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We studied the D3-type cyclin function during gynoecium development in Arabidopsis and how they are related to the hormone cytokinin and the transcription factor SPATULA. Growth throughout the life of plants is sustained by cell division and differentiation processes in meristematic tissues. In Arabidopsis, gynoecium development implies a multiphasic process where the tissues required for pollination, fertilization, and seed development form. The Carpel Margin Meristem (CMM) is a mass of undifferentiated cells that gives rise to the gynoecium internal tissues, such as septum, ovules, placenta, funiculus, transmitting tract, style, and stigma. Different genetic and hormonal factors, including cytokinin, control the CMM function. Cytokinin regulates the cell cycle transitions through the activation of cell cycle regulators as cyclin genes. D3-type cyclins are expressed in proliferative tissues, favoring the mitotic cell cycle over the endoreduplication. Though the role of cytokinin in CMM and gynoecium development is highly studied, its specific role in regulating the cell cycle in this tissue remains unclear. Additionally, despite extensive research on the relationship between CYCD3 genes and cytokinin, the regulatory mechanism that connects them remains elusive. Here, we found that D3-type cyclins are expressed in proliferative medial and lateral tissues. Conversely, the depletion of the three CYCD3 genes showed that they are not essential for gynoecium development. However, the addition of exogenous cytokinin showed that they could control the division/differentiation balance in gynoecium internal tissues and outgrowths. Finally, we found that SPATULA can be a mechanistic link between cytokinin and the D3-type cyclins. The data suggest that the role of D3-type cyclins in gynoecium development is related to the cytokinin response, and they might be activated by the transcription factor SPATULA.

Cytokinins, which play crucial roles in shoot development, substantially affect grain yield. In rice, the OsRopGEF10-OsRAC3 module is associated with cytokinin signaling and crown root development. However, the effects of RopGEF-mediated cytokinin signaling on rice shoot development and grain yield remain unclear. In this study, we investigated the role of OsRopGEF10 in SAM development and the underlying mechanism. We showed that overexpression of OsRopGEF10 inhibited SAM and panicle development, leading to decreased grain yield. Intriguingly, the overexpression of a specific amino acid mutant of OsRopGEF10, designated gef10-W260S, was found to promote panicle development and grain yield. Further analysis using the BiFC assay revealed that the gef10-W260S mutation disrupted the recruitment of rice histidine phosphotransfer proteins (OsAHP1/2) to the plasma membrane (PM), thereby promoting cytokinin signaling. This effect was corroborated by a dark-induced leaf senescence assay, which revealed an increased cytokinin response in the gef10-W260S ectopic expression lines, whereas the overexpression lines presented a suppressed cytokinin response. Moreover, we revealed that the enhanced panicle development in the gef10-W260S lines was attributable to the upregulated expression of several type-B response regulators (RRs) that are crucial for panicle development. Collectively, these findings revealed the negative regulatory function of OsRopGEF10 in the development of the shoot apical meristem (SAM) via interference with cytokinin signaling. Our study highlights the promising role of OsRopGEF10 as a potential target for regulating SAM and panicle development in rice, revealing a valuable breeding strategy for increasing crop yield. [ABSTRACT FROM AUTHOR]

Summary: Phytohormones possess unique chemical structures, and their physiological effects are regulated through intricate interactions or crosstalk among multiple phytohormones. MALDI‐MSI enables the simultaneous detection and imaging of multiple hormones. However, its application for tracing phytohormones is currently restricted by low abundance of hormone in plant and suboptimal matrix selection.2,4‐Dihydroxy‐5‐nitrobenzoic acid (DHNBA) was reported as a new MALDI matrix for the enhanced detection and imaging of multiple phytohormones in plant tissues. DHNBA demonstrates remarkable sensitivity improvement when compared to the commonly used matrix, 2,5‐dihydroxybenzoic acid (DHB), in the detection of isoprenoid cytokinins (trans‐zeatin (tZ), dihy‐drozeatin (DHZ), meta‐topolin (mT), and N6‐(Δ2‐isopentenyl) adenine (iP)), jasmonic acid (JA), abscisic acid (ABA), and 1‐aminocyclo‐propane‐1‐carboxylic acid (ACC) standards.The distinctive properties of DHNBA (i.e. robust UV absorption, uniform matrix deposition, negligible background interference, and high ionization efficiency of phytohormones) make it as an ideal matrix for enhanced detection and imaging of phytohormones, including tZ, DHZ, ABA, indole‐3‐acetic acid (IAA), and ACC, by MALDI‐MSI in various plant tissues, for example germinating seeds, primary/lateral roots, and nodules.Employing DHNBA significantly enhances our capability to concurrently track complex phytohormone biosynthesis pathways while providing precise differentiation of the specific roles played by individual phytohormones within the same category. This will propel forward the comprehensive exploration of phytohormonal functions in plant science. [ABSTRACT FROM AUTHOR]

Plants encounter many biotic entities, such as fungi, bacteria, and nematodes, which induce biotic stress that disrupts normal metabolism and limits the growth and productivity of plants. Currently, the use of plant growth-promoting bacterial endophytes instead of synthetic fungicides is intriguingly eco-friendly. An in vitro and in vivo antagonistic approach using Bacillus amyloliquefaciens RaSh1 was used to mimic the pathogenic effect of Alternaria alternata. The results showed that B. amyloliquefaciens significantly inhibited pathogenic fungal growth in vitro. Further, Capsicum annuum L. (pepper plants) were grown and subjected to inoculation with B. amyloliquefaciens and infected with A. alternata, and then the growth attributes, photosynthetic pigments, physio-biochemical parameters, and the level of endogenous phytohormones were assessed. Under the pathogen attack, the main responses, such as plant length, total fresh and dry weights, total chlorophylls, and pigments, were reduced, accompanied by increases in H2O2. As well, infection of pepper with A. alternata caused downregulation in the plant hormonal system by significantly decreasing gibberellins, indole-3-acetic acid, abscisic acid, as well as cytokinin concentrations. Although, with B. amyloliquefaciens application, an enhancement in growth, photosynthetic pigments, proline, thiol content, phenylalanine ammonia-lyase, and peroxidase in pepper plant leaves appeared while the content of H2O2 decreased. Endogenous phytohormones were found to be upregulated in B. amyloliquefaciens-inoculated and diseased plants. The current study found that B. amyloliquefaciens RaSh1 rescued pepper plant growth by modulating antioxidant defense and regulating hormones, and could be used to control A. alternata in an environmentally friendly manner while maintaining sustainable agriculture and food security. [ABSTRACT FROM AUTHOR]

Plant growth regulators are an appealing and fast-track method for overcoming the drastic effects of drought. Paclobutrazol (PBZ), a member of the triazole family, is a versatile chemical compound that acts as a growth regulator and retardant. This study assessed the effect of two concentrations of PBZ (30 and 60 mg L–1) on strawberry plants under two drought stress levels [40% and 80% field capacity (FC)] and 100% FC set as the control. The findings revealed that drought significantly affected strawberry plants, elevating the levels of reactive oxygen species (ROS) like hydrogen peroxide (H2O2), hydroxide ion (OH–), and superoxide ion (O2–), and reactive carbonyl species (RCS) like malondialdehyde (MDA), methylglyoxal (MG), 4-hydroxy-(E)-2-hexenal (HEE), acetone, propionaldehyde (PD), acetaldehyde (ACD), and formaldehyde (FMD), due to decreased antioxidant activities. The study also found that glutathione (GSH) is crucial in ROS and RCS scavenging. In addition, the presence of thiol groups (–SH compounds) in strawberry plants under moderate and severe drought stress was a noteworthy finding. Due to excess thiol production, drought stress significantly decreased MDA, MG, HEE, PD, ACD, FMD, and acetone levels. However, PBZ application decreased the total thiol content in strawberry leaves. Furthermore, PBZ improved plant growth and development by modulating the production of endogenous growth hormones such as abscisic acid, indole-3-acetic acid, ethylene, gibberellic acid, strigolactones, and brassinosteroids, while increasing cytokinin levels. These changes led to enhanced enzymatic and non-enzymatic antioxidant activities, reduced stomatal conductance, increased relative water content in leaves, improved chlorophyll content, elevated photosynthetic rate, and ultimately enhanced increased fruit yield. Moreover, drought stress enhanced metabolic activity (α-tocopherol, β-carotene, total phenolic content, anthocyanin, and proline) in strawberry plants, indicating that metabolites also function as stress scavengers/protectors. This study shed light on crucial physiological mechanisms underlying ROS- and RCS-induced oxidative stresses and their management in strawberry plants. [ABSTRACT FROM AUTHOR]

Eggplant (Solanum melongena L.) is one of the essential vegetables worldwide, and cultivated genotypes of eggplant suffer from numerous abiotic and biotic stresses. A reproducible and efficient plant regeneration system is crucial for applying molecular breeding methods to overcome the difficulties of conventional breeding programs to improve eggplant germplasm, such as genetic transformation and genome editing techniques. The three explant types, cotyledon, hypocotyl, and leaf, were obtained from two different cultivars, Pusa purple long (PL) and Pusa green round (GR) of eggplant. Three explants were cultivated on media augmented with a variety of cytokinins, including BAP, mT, and ZEA, in different concentrations. The media supplemented with mT at 8.28 µM generated the highest number of shoots, which showed the optimum regeneration efficiency for all three explants in two eggplant genotypes. The cotyledon explants generated the optimum number of shoot buds on the medium amended with low concentrations of BAP (2.22 µM), KIN (2.32 µM), and ZEA (4.56 µM), and mT at 8.28 µM. The mT (8.28 µM) and BAP at 2.22 µM combinations produced 25.8 and 18.3 shoots in PL and GR genotypes, respectively. The addition of various concentrations of IAA (1.43 to 5.71 µM), IBA (1.23 to 4.92 µM), and NAA (1.34 to 5.37 µM) in combination with mT (8.28 µM) were evaluated to find out their role on the induction and proliferation of numerous shoot buds from cotyledon explants of two cultivars of eggplant. The medium augmented with mT (8.28 µM) and IAA (2.85 µM) produced 26.4 shoots and 17.8 shoots in cotyledon explants of PL and GR cultivars, respectively. The optimum rooting efficiency of shoots was recorded on the medium containing the IAA (5.71 µM) and produced complete plantlets. The plantlets showed 100% similarity with their mother plants. [ABSTRACT FROM AUTHOR]

Coffea spp. are remarkable sources of phytochemicals, but the lack of a well-defined culture medium aimed at the induction of non-embryogenic and friable callus hampers the establishment of plant cell suspension cultures for large-scale production of valuable compounds. In this paper, we describe a one-medium protocol suitable to obtain both callus and cell suspension cultures from leaves of two elite cultivars of C. arabica. The protocol was developed through an iterative process involving the determination of the best concentration of auxin and cytokinin, their optimal ratio, as well as the most effective molecule of either hormone class. Young leaves were found to be a good and easy-to-use explant source for callus induction and proliferation, provided that a cytokinin was present in association with a chlorinated auxin in a full strength, semi-solid MS medium. The best results were obtained by hormone concentration and combination of 1 mg/L of both kinetin and 2,4,5-trichlorophenoxyacetic acid. The same ratio of these growth regulators was conveniently used for the development and stabilization of cell suspension cultures in liquid MS medium. When grown in darkness, stabilized suspension cultures showed a fine and homogeneous texture, with a 10-fold biomass increase within 25 days and a cell viability > 90%. In addition, the phytochemical profile revealed the presence of the most widely studied coffee compounds. The protocol can be applied to obtain adequate amounts of cell biomass for use in physiological studies concerning the production of secondary metabolites.Key messages: A protocol for callus induction and undifferentiated cell suspensions establishment in Coffea arabica was developed. This technique represents a useful tool for in vitro production of remarkable phytochemicals from coffee. [ABSTRACT FROM AUTHOR]

The shoot apical meristem (SAM) contains pluripotent stem cells that produce all the aerial parts of the plant. Stem cells undergo asymmetric cell divisions to self-renew and to produce differentiating cells. Our research focused on unraveling the mechanisms governing the specification of these two distinct cell fates following the stem cell division. For this purpose, we used the model organism Physcomitrium patens, which features a singular pluripotent stem cell known as the gametophore apical cell. We show that the activity of cytokinins, critical stem cell regulators, is restricted to the gametophore apical cell due to the specific localization of PpLOG, the enzyme responsible for cytokinin activation. In turn, PpTAW, which promotes differentiating cell identity of the merophyte, is excluded from the gametophore apical cell by the action of cytokinins. We propose a cytokinin-based model for the establishment of asymmetry in the pluripotent stem cell division. [ABSTRACT FROM AUTHOR]

Leaves play a crucial role in photosynthesis and respiration, ultimately affecting the final grain yield of crops, including wheat (Triticum aestivum L.); however, the molecular mechanisms underlying wheat leaf development remain largely unknown. Here, we isolated a narrow-leaf gene, TaWAK2-A, through a map-based cloning strategy. TaWAK2-A encodes a wall-associated kinase (WAK), for which a single Ala-to-Val amino acid substitution reduces the protein stability, leading to a narrow-leaf phenotype in wheat. Further investigation suggests that TaWAK2 directly interacts with and phosphorylates TaNAL1, a trypsin-like serine/cysteine protease. The phosphorylated TaNAL1 is then involved in the degradation of the zinc finger transcription factor TaDST, which acts as a repressor of leaf expansion by activating the expression of the cytokinin oxidase gene TaCKX9 and triggering in vivo cytokinin degradation. Therefore, our findings elucidate a signaling cascade involving TaWAK2-TaNAL1-TaDST that sheds light on the regulation of wheat leaf development. [ABSTRACT FROM AUTHOR]

Parthenocarpic fruits, known for their superior taste and reliable yields in adverse conditions, develop without the need for fertilization or pollination. Exploring the physiological and molecular mechanisms behind parthenocarpic fruit development holds both theoretical and practical significance, making it a crucial area of study. This review examines how plant hormones and MADSbox transcription factors control parthenocarpic fruit formation. It delves into various aspects of plant hormones-including auxin, gibberellic acid, cytokinins, ethylene, and abscisic acid--ranging from external application to biosynthesis, metabolism, signaling pathways, and their interplay in influencing parthenocarpic fruit development. The review also explores the involvement of MADS family gene functions in these processes. Lastly, we highlight existing knowledge gaps and propose directions for future research on parthenocarpy. [ABSTRACT FROM AUTHOR]

ABSTRACT Salinization poses a significant challenge in agriculture, exacerbated by anthropogenic global warming. Biostimulants, derived from living microorganisms or natural extracts, have emerged as valuable tools for conventional and organic agriculture. However, our understanding of the molecular mechanisms underlying the effects of biostimulants is very limited, especially in crops under real cultivation conditions. In this study, we adopted an integrative approach to investigate the effectiveness of the combined application of plant growth‐promoting bacterium (Bacillus megaterium strain BM08) and a non‐microbial biostimulant under control conditions (normal watering) and salt stress. After confirming the yield increase under both conditions, we investigated the molecular mechanisms underlying the observed effect by measuring a number of physiological parameters (i.e., lipid peroxidation, antioxidants, chlorophylls, total phenolics and phytohormone content), as well as RNA sequencing and primary metabolite analyses. Our findings reveal that the combined effect of the microbial and non‐microbial biostimulants led to a decrease in the antioxidant response and an up‐regulation of genes involved in cytokinin biosynthesis under salt stress conditions. This, in turn, resulted in a higher concentration of the bioactive cytokinin, isopentenyladenosine, in roots and leaves and an increase in γ‐aminobutyric acid, a non‐proteic amino acid related to abiotic stress responses. In addition, we observed a decrease in malic acid, along with an abscisic acid (ABA)‐independent up‐regulation of SR‐kinases, a family of protein kinases associated with abiotic stress responses. Furthermore, we observed that the single application of the non‐microbial biostimulant triggers an ABA‐dependent response under salt stress; however, when combined with the microbial biostimulant, it potentiated the mechanisms triggered by the BM08 bacterial strain. This comprehensive investigation shows that the combination of two biostimulants is able to elicit a cytokinin‐dependent response that may explain the observed yield increase under salt stress conditions. [ABSTRACT FROM AUTHOR]

Cadaba trifoliata (Roxb.) Wight & Arn. (Capparaceae) is an occasional and endemic tree species of the Peninsular India. In this study, an effective in vitro regeneration system is reported for the first time for this tree, and the impact of growth regulators on the micro-morphometric growth modulations was assessed. Node explants were cultivated on Murashige and Skoog (MS) medium containing 3 types of cytokinins viz., N6-benzyladenine (BA), N6-furfuryladenine (kinetin/Kin), and N6-(meta-hydroxybenzyl)adenine (meta-Topolin/mT). The MS medium with mT at 1.0 mg/L was found the most efficient cytokinin for bud break, resulting in a 90.3% organogenic response and producing 8.0 shoots/explants. Conversely, MS medium with 1.5 mg/L BA produced 4.0 shoots, and only 3.3 shoots resulted in 2.0 mg/L Kin. Additionally, a combination of mT (0.5 mg/L) and 0.25 mg/L indole-3-acetic acid (IAA) increased regeneration frequencies and a maximum of 23.0 shoots (5.4 cm length) were amplified, in contrast a combination of BA + IAA and Kin + IAA resulted in a lesser number of shoots comparatively with shoot tip necrosis. Microscopic analysis showed that the leaves developed on the optimal mT and IAA combination were structurally superior with moderately differentiated cuticle, uniform epidermal layers, and increased mesophyll density and vascular elements. The leaves from BA + IAA and Kin + IAA treatments exhibited micro-structural abnormalities. The highest rhizogenic response (95.8%) and a considerable number of roots (5.0 roots with 4.3 cm length) were regenerated from the shoots derived from mT and IAA combination on 1.25 mg/L indole-3-butyric acid (IBA). About 91.7% of the regenerated plantlets survived during ex vitro acclimatization. The study thus highlights the pivotal role of mT in stimulating the in vitro regeneration and alleviation of micro-structural and physiological disorders in cultures of C. trifoliata. [ABSTRACT FROM AUTHOR]

Promoting more floret primordia within a spike to acquire fertile potential during the differentiation and pre-dimorphism phases is critical for increasing the number of fertile florets per spike (NFFs). However, it is yet unknown the physiological mechanism regulating the complex and dynamic process. This study aimed to clarify how intra-spike hormones, pigments, and assimilates coordinate with each other to regulate spike morphology and then floret primordia development. A two-year field experiment was conducted with two winter wheat genotypes: N50 (big-spike with greater NFFs) and SM22 (mediumspike with fewer NFFs). We monitored high temporal and spatial-resolution changes in the number and morphology of floret primordia within a spike, as well as in intra-spike hormones, pigments, and assimilates. Our results revealed that the big-spike genotype had more NFFs than the medium-spike genotype, not only because they had more spikelets, but also because they had greater NFFs mainly at central spikelets. More floret primordia at central spikelets had sufficient time to develop and acquire fertile potential during the differentiation phase (167-176 d after sowing, DAS) and the pre-dimorphism phase (179 DAS) for the big-spike genotype than the medium-spike genotype. Floret primordia with fertile morphology during the pre-dimorphism phase always developed into fertile florets during the dimorphism phase. Those early-developed floret primordia most proximal and intermediate to the rachis in the big-spike genotype developed faster than the medium-spike genotype. Correspondingly, the spike dry matter and pigments (chlorophyll a, chlorophyll b, carotene, and carotenoids) content during 170-182 DAS, auxin (IAA) and cytokinin (CTK) content on 167 DAS were significantly higher in the big-spike genotype than in the medium-spike genotype, while jasmonic acid (JA) content was significantly lower in the big-spike genotype compared to the medium-spike genotype during 167-182 DAS. Since the significant differences in intra-spike hormone content of the two genotypes appear earlier than those in dry matter and pigments, we propose a possible model that helped the N50 genotype (big-spike) to form more fertile florets, taking the intra-spike hormone content as a signaling molecule induced assimilates and pigments synthesis, which accelerated the development of more floret primordia during the differentiation phase and then acquired fertile potential during the pre-dimorphism phase, finally improved the NFFs. Our high temporal and spatial-resolution analysis provides an accurate time window for precision cultivation and effective physiological breeding to improve the number of fertile florets in wheat. [ABSTRACT FROM AUTHOR]

Seed vigor is a pivotal indicator of seed quality, and timely harvesting is essential for maize seed vigor. The seeds and embryos of maize inbred lines JNY6F and PH4CV at different maturity stages were selected as study materials, the phenotypic characteristics and seed vigor indexes of which were detected, and the soluble sugars, antioxidant enzyme activity, and pythormones [auxin (IAA), cytokinins (CTKs), gibberellins (GAs), and abscisic acid (ABA)] in fresh immature embryos were analyzed. The analysis results indicated that the seeds of JNY6F and PH4CV reached physiological maturity at 35 and 50 days after pollination, which were the optimal harvest times for JNY6F and PH4CV, respectively, as the embryonic morphology of which had been estabilished, and the seed vigor of which reached their peaks at these two stages. The seed vigor indexes showed significant negative correlations with the levels of soluble reducing sugar, total soluble sugar, and four pythormones in the immature embryos, but were highly positively correlated with catalase (CAT) and peroxidase (POD) enzyme activities. In summary, our findings offer valuable insights into the ideal harvest time and physiological mechanisms underlying the seed vigor of maize inbred lines, and contribute to the enhancement of seed quality and agricultural practices in maize inbred line production. [ABSTRACT FROM AUTHOR]

In this study, we document the primary structural changes that occur during the seed development of Paphiopedilum spicerianum (Rchb.f.) Pfitzer, an endangered species with high horticultural value. Within a defined timeline, our results offer insights into the connection between these structural changes in seeds and their germination percentage. The optimum germination was recorded for immature seeds collected at 180 to 210 days after pollination (DAP), during which the embryos are in the late globular stage and the suspensor begins to degenerate. As seeds continued to mature by 240 DAP, there was a gradual decline in germination. Histochemical staining of mature seeds reveals that only the inner seedcoat and the surface of the embryo exhibit positive reactions to the Nile red stain, suggesting a relatively weak coat-imposed dormancy. This weaker dormancy may contribute to the higher germination observed in mature seeds of P. spicerianum compared with other challenging-to-germinate species. Of the cytokinins examined, 6-(γ,γ-dimethylallylamino)purine (2iP), kinetin (KN), and 6-benzylaminopurine (BA) exhibited a stimulating effect on germination, concurrently enhancing the formation of amorphous protocorms. [ABSTRACT FROM AUTHOR]

SUMMARY: WHIRLY1 is a chloroplast‐nucleus located DNA/RNA‐binding protein with functions in development and stress tolerance. By overexpression of HvWHIRLY1 in barley, one line with a 10‐fold and two lines with a 50‐fold accumulation of the protein were obtained. In these lines, the relative abundance of the nuclear form exceeded that of the chloroplast form. Growth of the plants was shown to be compromised in a WHIRLY1 abundance‐dependent manner. Over‐accumulation of WHIRLY1 in chloroplasts had neither an evident impact on nucleoid morphology nor on the composition of the photosynthetic apparatus. Nevertheless, oeW1 plants were found to be compromised in the light reactions of photosynthesis as well as in carbon fixation. The reduction in growth and photosynthesis was shown to be accompanied by a decrease in the levels of cytokinins and an increase in the level of jasmonic acid. Gene expression analyses revealed that in nonstress conditions the oeW1 plants had enhanced levels of pathogen response (PR) gene expression indicating activation of constitutive defense. During growth in continuous light of high irradiance PR gene expression increased indicating that under stress conditions oeW1 are capable to further enhance defense. Significance Statement: With regard to its dual localization in chloroplasts and nucleus WHIRLY1 is an excellent communicator in retrograde signaling. Previous studies with barley showed that a knockdown of WHIRLY1 compromises acclimation to environment. Here we show that overexpression of WHIRLY1 in barley, leading to an over‐accumulation of the protein in both chloroplasts and nucleus, improves stress resistance whereas it has a negative impact on photosynthesis and growth. [ABSTRACT FROM AUTHOR]

Background and Aims Turions are vegetative, dormant overwintering organs formed in aquatic plants in response to unfavourable ecological conditions. Contents of cytokinin (CK), auxin metabolites and abscisic acid (ABA) as main growth and development regulators were compared in innately dormant autumnal turions of 22 aquatic plant species of different functional ecological or taxonomic groups with those in non-dormant winter apices in three aquatic species and with those in spring turions of four species after their overwintering. Methods The hormones were analysed in miniature turion samples using ultraperformance liquid chromatography coupled with triple quadrupole mass spectrometry. Key Results In innately dormant turions, the total contents of each of the four main CK types, biologically active forms and total CKs differed by two to three orders of magnitude across 22 species; the proportion of active CK forms was 0.18–67 %. Similarly, the content of four auxin forms was extremely variable and the IAA proportion as the active form was 0.014–99 %. The ABA content varied from almost zero to 54 µmol kg−1 dry weight and after overwintering it usually significantly decreased. Of all functional traits studied, hormone profiles depended most on the place of turion sprouting (surface vs bottom) and we suggest that this trait is crucial for turion ecophysiology. Conclusions The key role of ABA in regulating turion dormancy was confirmed. However, the highly variable pattern of the ABA content in innately dormant and in overwintered turions indicates that the hormonal mechanism regulating the innate dormancy and its breaking in turions is not uniform within aquatic plants. [ABSTRACT FROM AUTHOR]

Camellia drupifera is an important woody oil plant in South China, renowned for its seed oil that is rich in unsaturated fatty acids and possesses significant antioxidant, anti-cancer, and immune-enhancing properties. The low fruit-setting rate of C. drupifera is influenced by multiple factors, including flowering stage climate, flowering habits, pollination biology, soil conditions, and self-incompatibility. Among these, large-scale pure forest plantations are the primary cause of the low fruit-setting rate. Although previous studies have explored the impact of self-incompatibility on fruit-setting in C. drupifera, research on the dynamic changes of endogenous substances during the flowering stage in pure forest environments remains limited. Research findings indicate that tannase activity is relatively high in the pistils of C. drupifera, creating a favorable environment for pollen tube growth. Plant hormones such as indole-3-acetic acid (IAA), cytokinin (CTK), gibberellin (GA), and ethylene (ETH) regulate the development and aging of floral organs through complex interactions. Specifically, high levels of IAA in the pistil promote pollen tube growth, while changes in ETH and ABA are closely related to the aging of floral organs. Under oxidative stress conditions, high levels of H2O2 in the pistil may contribute to self-incompatibility. The activity of superoxide dismutase (SOD) in the floral organs during the flowering stage is significantly higher compared to peroxidase (POD) and catalase (CAT), highlighting the critical role of SOD in regulating oxidative stress during this stage. This study provides new insights into the changes in endogenous substances in the floral organs of C. drupifera during the flowering stage. It offers theoretical references for understanding its sexual reproduction process and for the application of plant growth regulators to improve fruit setting. [ABSTRACT FROM AUTHOR]

Exposure to abiotic stresses accelerates leaf senescence in most crop plant species, thereby reducing photosynthesis and other assimilatory processes. In some cases, genotypes with delayed leaf senescence (i.e. 'stay-green') show stress resistance, particularly in cases of water deficit, and this has led to the proposal that senescence delay improves crop performance under some abiotic stresses. In this review, we summarize the evidence for increased resistance to abiotic stress, mostly water deficit, in genotypes with delayed senescence, and specifically focus on the physiological mechanisms and agronomic conditions under which the stay-green trait may ameliorate grain yield under stress. [ABSTRACT FROM AUTHOR]

Background: Kale, a versatile cruciferous crop, valued for its pro-health benefits, stress resistance, and potential applications in forage and cosmetics, holds promise for further enhancement of its bioactive compounds through in vitro cultivation methods. Micropropagation techniques use cytokinins (CKs) which are characterized by various proliferative efficiency. Despite the extensive knowledge regarding CKs, there remains a gap in understanding their role in the physiological mechanisms. That is why, here we investigated the effects of three CKs – kinetin (Kin), 6-benzylaminopurine (BAP), and 2-isopentenyladenine (2iP) – on kale physiology, antioxidant status, steroidal metabolism, and membrane integrity under in vitro cultivation. Results: Our study revealed that while BAP and 2iP stimulated shoot proliferation, they concurrently diminished pigment levels and photosynthetic efficiency. Heightened metabolic activity in response to all CKs was reflected by increased respiratory rate. Despite the differential burst of ROS, the antioxidant properties of kale were associated with the upregulation of guaiacol peroxidase and the scavenging properties of ascorbate rather than glutathione. Notably, CKs fostered the synthesis of sterols, particularly sitosterol, pivotal for cell proliferation and structure of membranes which are strongly disrupted under the action of BAP and 2iP possibly via pathway related to phospholipase D and lipoxygenase which were upregulated. Intriguingly, both CKs treatment spurred the accumulation of sitostenone, known for its ROS scavenging and therapeutic potential. The differential effects of CKs on brassicasterol levels and brassinosteroid (BRs) receptor suggest potential interactions between CKs and BRs. Conclusion: Based on the presented results we conclude that the effect evoked by BAP and 2iP in vitro can improve the industrial significance of kale because this treatment makes possible to control proliferation and/or biosynthesis routes of valuable beneficial compounds. Our work offers significant insights into the nuanced effects of CKs on kale physiology and metabolism, illuminating potential avenues for their application in plant biotechnology and medicinal research. [ABSTRACT FROM AUTHOR]

In this study, the effects of various light treatments, growth regulators and culture media (agar-solidified and liquid) on in vitro propagation of Alternanthera reineckii Briq. Were evaluated. In in vitro experiments were used red, blue, and white LEDs alone and various combinations of red and blue LEDs. Different levels of 6-benzylaminopurine (BAP) and Kinetin (KIN), ranging from 0.25 mg/L to 1 mg/L, were introduced into the solid and liquid Murashige and Skoog (MS) basal medium. In solid culture, the highest number of shoots per explant (16.67 shoots/explant) was observed when utilizing a proportion of 1:2 red/blue LEDs in MS medium supplemented with 1 mg/L BAP. On the other hand, in the liquid culture, 15.13 shoots/explant were obtained with 1 mg/L BAP under a 2:1 red/blue LEDs configuration. During the experiments involving KIN, 10.42 shoots/explant were observed in the solid culture conditions with 1 mg/L of KIN under a lighting configuration of 1:2 red/blue LEDs. On the other hand, a total of 10.62 shoots/explant was attained in the liquid MS medium with 0.50 mg/L of KIN under a lighting configuration of 2:1 red/blue LEDs. As a result, LED lights were found to be better than fluorescent lights for multiple propagations of A. reineckii. Moreover, higher shoot numbers and longer shoots were achieved with red and blue LED light combinations. [ABSTRACT FROM AUTHOR]

The negative effects of salt stress on plants and their environment are increasing dramatically day by day, and it is crucial for plants to develop salt tolerance with various applications and biotechnological approaches. For this purpose, it is possible to improve salt tolerance in plants through different studies using controlled and uniform in vitro cultures, which are an alternative approach to greenhouse and pot experiments that affected by external environmental conditions. In this study, 24-epibrassinolide (24-epiBL) was used for increasing salt tolerance in in vitro shoot tip cultures of tomato M-28 hybrid cultivar. Shoot tips of 10-day sterile seedlings were placed in MS medium supplemented with 2 mg L-1 K + 0.4 mg L-1 NAA in a 12-day culture period, and 12-day plantlets soaked in 24-epiBL solutions (0, 1, 2 µM) were transferred to MS medium containing different concentrations of NaCl (0, 20, 40, 60, 80, 100 mM). After 20 days, the plantlets derived from in vitro cultures were used to assess growth (length, fresh and dry weight of plantlets) and biochemical parameters (pigment, MDA, proline, total soluble protein contents, POX and SOD enzyme activities). All growth and biochemical parameters, including pigment and total soluble protein content, were adversely impacted by salt stress (particularly at 40, 60, 80, and 100 Mm NaCl concentrations). However, MDA, proline content, as well as SOD and POX enzyme activity, increased as a results of oxidative stress at the same NaCl concentrations. As a result, NaCl responses in plant differed between various NaCl and 24-epiBL concentrations, and the different defense strategies combine multiple tolerance mechanisms. Therefore, this study, indicates that pretreatment of 24-epiBL to plantlets derived from shoot tips of the tomato M-28 hybrid cultivar played crucial role in mitigating the effects of salt stress. [ABSTRACT FROM AUTHOR]

Fluorinated cytokinins have emerged as promising alternatives to traditional cytokinins in Phalaenopsis plant tissue culture, offering enhanced stability and bioactivity. However, their metabolic fate and impact on endogenous cytokinin profiles remain largely unexplored. This study builds upon previous research to investigate the comparative metabolism of the traditional cytokinin 6-Benzylaminopurine (BA) with the successful alternatives 6-(3-fluorobenzylamino)purine (FmT) and 6-(3-fluorobenzylamino)purine 9-riboside (FmTR). Additionally, this study examines the impact of another crucial factor, the use of ventilated versus closed containers, on metabolic processes. The results revealed the distinct metabolic profiles associated with each treatment, highlighting the complex interplay between exogenous and endogenous cytokinin levels. This study is the first to investigate the effects of these stable, synthetic, and exogenous cytokinins on the naturally occurring cytokinin levels and their metabolites in micropropagated Phalaenopsis. Additionally, we proposed an alternative inactivation pathway involving the conversion of FmTR and BA to pT and pTR. These findings provide valuable insights into the intricate relationship between cytokinin metabolism and plant growth under in vitro conditions. [ABSTRACT FROM AUTHOR]

Isoprene, a volatile hydrocarbon, is typically emitted from the leaves of many plant species. Given its well‐known function in plant growth and defense aboveground, we examined its effects on root physiology. We used isoprene‐emitting (IE) lines and a non‐emitting (NE) line of Arabidopsis and investigated their performance by analyzing root phenotype, hormone levels, transcriptome, and metabolite profiles under both normal and salt stress conditions. We show that IE lines emitted tiny amounts of isoprene from roots and showed an increased root/shoot ratio compared with NE line. Isoprene emission exerted a noteworthy influence on hormone profiles related to plant growth and stress response, promoting root development and salt‐stress resistance. Methyl erythritol 4‐phosphate pathway metabolites, precursors of isoprene and hormones, were higher in the roots of IE lines than in the NE line. Transcriptome data indicated that the presence of isoprene increased the expression of key genes involved in hormone metabolism/signaling. Our findings reveal that constitutive root isoprene emission sustains root growth under saline conditions by regulating and/or priming hormone biosynthesis and signaling mechanisms and expression of key genes relevant to salt stress defense. [ABSTRACT FROM AUTHOR]

Abstract Background Kale, a versatile cruciferous crop, valued for its pro-health benefits, stress resistance, and potential applications in forage and cosmetics, holds promise for further enhancement of its bioactive compounds through in vitro cultivation methods. Micropropagation techniques use cytokinins (CKs) which are characterized by various proliferative efficiency. Despite the extensive knowledge regarding CKs, there remains a gap in understanding their role in the physiological mechanisms. That is why, here we investigated the effects of three CKs – kinetin (Kin), 6-benzylaminopurine (BAP), and 2-isopentenyladenine (2iP) – on kale physiology, antioxidant status, steroidal metabolism, and membrane integrity under in vitro cultivation. Results Our study revealed that while BAP and 2iP stimulated shoot proliferation, they concurrently diminished pigment levels and photosynthetic efficiency. Heightened metabolic activity in response to all CKs was reflected by increased respiratory rate. Despite the differential burst of ROS, the antioxidant properties of kale were associated with the upregulation of guaiacol peroxidase and the scavenging properties of ascorbate rather than glutathione. Notably, CKs fostered the synthesis of sterols, particularly sitosterol, pivotal for cell proliferation and structure of membranes which are strongly disrupted under the action of BAP and 2iP possibly via pathway related to phospholipase D and lipoxygenase which were upregulated. Intriguingly, both CKs treatment spurred the accumulation of sitostenone, known for its ROS scavenging and therapeutic potential. The differential effects of CKs on brassicasterol levels and brassinosteroid (BRs) receptor suggest potential interactions between CKs and BRs. Conclusion Based on the presented results we conclude that the effect evoked by BAP and 2iP in vitro can improve the industrial significance of kale because this treatment makes possible to control proliferation and/or biosynthesis routes of valuable beneficial compounds. Our work offers significant insights into the nuanced effects of CKs on kale physiology and metabolism, illuminating potential avenues for their application in plant biotechnology and medicinal research.

India has taken a huge leap in the seaweed aquaculture sector, and Kappaphycus alvarezii is the most prominent carrageenophyte cultivated so far. With the ever-increasing demands for seaweed feedstock, the quality of planting material would determine the extent of the expansion of commercial farming. The current study is a sequel to our previous investigation on the long-distance transport of K. alvarezii planting material. The present work determines the effect of a bio-stimulant AMPEP (Ascophyllum Marine Plant Extract Powder) in imparting tolerance to the translocated planting material against desiccation. Various regulatory components like phytohormones; antioxidant enzymes (CAT, APX, GR); and metabolic components were assessed for day 0 (immediately after translocation) and day 1 (after 24 h of rehydration). It was observed that more than 84% moisture content was retained in translocated and AMPEP-treated translocated samples. After 24 h of rehydration, the catalase activity increased from 45,343.3 Unit mg protein−1 in the control to 146,148 and 321,489.1 Unit mg protein−1 in translocated and AMPEP-treated translocated biomass respectively. Similarly, ascorbate peroxidase activity increased from 0.3 Unit mg protein−1 to 2 Unit mg protein−1 in translocated and 1.3 Unit mg protein−1 in AMPEP-treated translocated biomass on day 1, which is significantly higher than their respective day 0 values. Glutathione reductase activity, on the other hand, decreased significantly on day 1 as compared to day 0. The activity increased significantly from 18.9 Unit mg protein−1 to 25.7 and 276 Unit mg protein−1, respectively, in translocated and AMPEP-treated translocated biomass. Similarly, the concentration of metabolites palmitic and benzoic acids, which help the cells against oxidative stress, also increased significantly in AMPEP-treated translocated biomass. Auxin and cytokinin concentrations however decreased in AMPEP-treated translocated biomass on day 1 as compared to translocated. The implementation of management practice based on the study would ultimately lead to the enhancement of livelihood prospects of the coastal communities involved in seaweed farming. [ABSTRACT FROM AUTHOR]

Due to ongoing global climate changes and anthropogenic stress, soil drought has emerged as a significant threat, hindering plant growth, development, and resulting in crop losses. While phytohormones play a vital role in the formation of stress resistance mechanisms, cytokinins, in particular, remain poorly understood in cultivated cereals. The objective of our study was to investigate the impact of soil drought on plant growth and the homeostasis of endogenous cytokinins in both the aerial parts and roots of winter rye (Secale cereale) during the initial stages of vegetation. We aimed to elucidate the relationship between growth processes and the balance of these phytohormones. The plants were cultivated in a phytochamber using sand culture, and drought stress was induced by withholding water from nine-day-old plants for a period of eight days. The shoots and roots of 17-day-old plants were collected when dehydrated plants reached the critical wilting point. The content of endogenous cytokinins was analyzed using HPLC-MS. Our findings revealed that the inhibition of shoot growth and root elongation in stressed plants coincided with a reduction in the content of trans-zeatin riboside. This observation suggests that trans-zeatin riboside acts as a growth regulator in winter rye under soil drought conditions. Moreover, we observed an elevation in the levels of trans-zeatin and isopentenyladenine in the shoots and roots of stressed rye plants, indicating the involvement of these hormones in the formation of a "protective anti-stress block." These results highlight the multifunctional activity of cytokinins and demonstrate their role in regulating various components of the water deficit response. Consequently, our study expands our understanding of the role of cytokinins in the development of stress resistance in cereals.

As a cell proliferation regulator involved in wide biological processes in plants, GRF-INTERACTING FACTOR (GIF) controls different tissues development. However, whether GIF participates in fruit development remains unclear. According to transcriptome data, we identified PbGIF1 was highly expressed during fruit development in cytokinins induced parthenocarpy pear. In the present study, the biofunction of PbGIF1 was initially verified. Overexpression of PbGIF1 promoted fruit size of transgenic tomato. The size of flesh fruit was not affected by cell expansion but the cell proliferation was promoted by overexpressing PbGIF1. The accelerated cell proliferation process was also observed in PbGIF1-overexpressed transgenic pear fruit calli. The transcriptional regulation of cytokinins on PbGIF1 was further confirmed by exogenous CPPU treatments in pear fruitlets. To investigate the underlying mechanism, the cytokinins-responded factor, PbRR1, was further focused on. The results of Yeast-one-hybrid assay suggested that PbRR1 can bind to the promoter sequence of PbGIF1. The transcriptional activation of PbRR1 on PbGIF1 was also confirmed by Dual-Luciferase assays. Taken together, the results showed that cytokinins control pear fruit development via the transcriptional activation of PbGIF1 by PbRR1.

Global warming has adversely affected Picea abies (L.) H. Karst. forests in Europe, prompting the need for innovative forest-breeding strategies. Somatic embryogenesis (SE) offers promise but requires protocol refinement. Understanding the molecular mechanisms governing somatic embryo development is essential, as oxidative stress plays a crucial role in SE regulation. Ascorbic acid (ASA), is a vital antioxidant that can potentially control oxidative stress. In the present study, we normalized ASA concentrations in induction and proliferation media to enhance embryogenic tissue (ET) regeneration and proliferation capacity of mature explants. The media were supplemented with ASA at 0 mg l-1, 25mg l-¹ 50mg l-¹100 mg l-1, and 200 mg l-1. The accumulation of hydrogen peroxide (H2O2) and endogenous phytohormones, including auxins, cytokinins, brassinosteroids, abscisic acid, and gibberellin, was measured in non-embryonic calli and ET. Subsequently, their impact on ET induction and multiplication was analyzed. Our results demonstrate that application of ASA at concentrations of 25 mg l-¹ and 200 mg l-¹ led to increased H2O2 levels, potentially inducing oxidative stress while simultaneously reducing the levels of all endohormone groups. Notably, the highest ET induction frequency (approximately 70%) was observed for ASA at 50 mg l-1. These findings will enhance SE induction procedures, particularly in more resistant explants, underscoring the significance of ASA application to culture media. [ABSTRACT FROM AUTHOR]

Yield of cotton (Gossypium hirsutum) does not always fall with high temperature (HT) even though this induces significant reductions in fruit retention. To investigate the underlying mechanisms, a greenhouse experiment was conducted with two temperature regimes [control treatment, 28 °C; high temperature (HT), 34 °C] for 7 d. Results showed HT did not significantly influence cotton yield, but reduced boll number and increased boll weight. The 13C distribution ratio of the leaf subtending the cotton boll (LSCB) decreased while that of the cotton boll increased under HT. Transcriptomic and proteomic analyses of the LSCB revealed up-regulated genes involved in cytokinin and jasmonic acid synthesis, as well as SWEET15 (GH_D01G0218), which positively regulated photosynthesis and transport photosynthate, ultimately leading to increased boll weight. After 7 d recovery from HT, the 13C distribution ratio of the LSCB increased while that of the cotton boll decreased. However, boll weight still increased, which was related to increased amylase and sucrose phosphate synthase activities and up-regulated sucrose transport genes in the main-stem leaf and capsule wall. Thus, both accelerated sucrose synthesis and transport in the LSCB under HT and increased sucrose supply ability of the main-stem leaf and capsule wall after recovery from HT contributed to an increased boll weight, which finally maintained cotton yield. [ABSTRACT FROM AUTHOR]

Cytokinins (CKs) are a group of N6-substituted signaling molecules whose biosynthesis and metabolism have been documented in all kingdoms of life, including vertebrates. While their biological relevance in vertebrate systems continues to be elucidated, they have broadly been documented with therapeutic effects in exogenous applications. In this study, we evaluated the virostatic potential of four types of CKs including, N6-isopentenyladenine (iP), N6-isopentenyladenosine (iPR), N6-isopentenyladenosine-5′monophosphate (iPMP), and 2-methylthiol-N6-isopentenyladenosine (2MeSiPR) against the ranavirus type species, frog virus 3 (FV3). Following concurrent treatment and infection, iP and iPR reduced viral replication by 33.8% and 59.6%, respectively, in plaque formation assays. A decrease in viral replication was also observed when CK exposure was limited to 12 h prior to infection, where iP and iPR reduced viral replication by 31% and 23.75%, respectively. Treatment with iP and iPR was also marked by 48% and 60% decreases in viral load over 72 h, respectively, as measured in single step growth curves. Plaque morphology was altered in vitro, as iP and iPR treatment increased plaque area by 83% and 112% with lytic zone formation also becoming more prevalent in corresponding treatments. Treatment with iPMP and 2MeSiPR resulted in no effect on viral kinetics in vitro. The results of this study are the first to provide evidence of CK antiviral activity against a DNA virus and highlight the importance of their structure for therapeutic investigations. [ABSTRACT FROM AUTHOR]

Callus cultures of the Iranian medicinal plant Salvia atropatana were initiated from three-week-old seedlings on Murashige and Skoog (MS) medium supplemented with α-naphthaleneacetic acid (NAA) and various cytokinins. Although all tested hormonal variants of the medium and explant enabled callus induction, the most promising growth was noted for N-(2-chloro-4-pyridyl)-N′-phenylurea (CPPU)-induced calli. Three lines obtained on this medium (cotyledon line-CL, hypocotyl line—HL, and root line—RL) were preselected for further studies. Phenolic compounds in the callus tissues were identified using UPLC–MS (ultra-performance liquid chromatography–mass spectrometry) and quantified with HPLC (high-performance liquid chromatography). All lines exhibited intensive growth and contained twelve phenolic acid derivatives, with rosmarinic acid predominating. The cotyledon-derived callus line displayed the highest growth index values and polyphenol content; this was exposed to different light-emitting diodes (LED) for improving biomass accumulation and secondary metabolite yield. Under LED treatments, all callus lines exhibited enhanced RA and total phenolic content compared to fluorescent light, with the highest levels observed for white (48.5–50.2 mg/g dry weight) and blue (51.4–53.9 mg/g dry weight) LEDs. The selected callus demonstrated strong antioxidant potential in vitro based on the 2,2′-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid) (ABTS), 2,2-diphenyl-1-picrylhydrazyl (DPPH), and ferric reducing antioxidant power (FRAP) tests. Our findings confirm that the S. atropatana callus system is suitable for enhanced rosmarinic acid production; the selected optimized culture provide high-quality plant-derived products. [ABSTRACT FROM AUTHOR]

A large group of horticulture species are propagated vegetatively through shoottip cuttings harvested from stock plants and planted to form adventitious roots. Adventitious rooting leads to establishing a carbohydrate sink in the region of root regeneration that is highly dependent on energy and carbon skeletons. We hypothesized that the timing of exogenous applications of cytokinin (CK) and boron (B)-molybdenum (Mo)-based products during adventitious root development can affect the flow of sugars from leaves to sinks, carbon allocation to the adventitious roots, and the quality of rooted cuttings. During this project, we aimed to determine if the application time of a CK/B-Mo-based product during the adventitious root development of unrooted cuttings would impact the source-to-sink relationship and, hence, affect plug growth and quality. A sink-strengthening commercial product based on cytokinin, B, and Mo was applied at four plug development stages plus a negative control as follows: T1, plants without product (control); T2, sticking stage (starting 24 hours after the sticking); T3, callus formation stage; T4, root development stage; and T5, toning stage. The root and shoot lengths and dry matter, number of leaves, leaf chlorophyll content, root-to-shoot ratio (based on dry matter), and nonstructural carbohydrate contents were measured. The timing of the application of the product impacted the root development, quality of the cuttings, and nonstructural carbohydrate content. Product application during the adventitious root dedifferentiation and induction phases (T2) resulted in the shortest root and shoot lengths, lowest dry matter accumulation, lowest nonstructural carbohydrate contents, and some phytotoxicity. Application during the initiation phase (T3) resulted in greater root length, total dry matter, and total soluble sugar contents compared with the control. Application during the expression phase (T4) resulted in the largest root length and mass and the highest sucrose contents. Applying the product when the roots had grown and reached all the edges of the growing media (T5) did not have any benefits compared with the control. This study provides new insights into the application timing of exogenous CKs, B, and Mo to generate a well-toned rooted coleus cutting and potential explanations in relation to nonstructural carbohydrate metabolism. [ABSTRACT FROM AUTHOR]

A two-year field experiment conducted under dryland conditions in semi-humid and drought-prone regions of China aimed to assess the effect of ammonia-oxidizing bacterial on maize water use efficiency and yield. A heterotrophic ammonia-oxidizing bacteria (HAOB) strain S2_8_1 was used. Six treatments were applied: (1) no irrigation + HAOB strain (DI), (2) no irrigation + blank culture medium (DM), (3) no irrigation control (DCK), (4) irrigation + HAOB (WI), (5) irrigation + blank culture medium (WM), and (6) irrigation control (WCK). Results revealed that HAOB treatment increased maize growth, yield, and water use efficiency over controls, regardless of whether the year was wet or dry. This improvement was attributed to the accelerated nitrification in the rhizosphere soil due to HAOB inoculation, which subsequently led to increased levels of leaf cytokinins. Overall, these findings suggest that HAOB inoculation holds promise as a strategy to boost water use efficiency and maize productivity in dryland agriculture. [ABSTRACT FROM AUTHOR]

Maize plant architecture influences planting density and, in turn, grain yield. Most of the plant architecture-related traits can be described as organ size. We describe a miniature maize mutant, Tiny plant 4 (Tip4), which exhibits reduced size of multiple organs and exhibits a semi-dominant monofactorial inheritance characteristic. Positional cloning confirmed that a 4-bp deletion in the NAC TF with transmembrane motif 1-Like (NTL) gene ZmNTL2, denoted as ZmNTL2△, confers the Tip4 mutation. qRT-PCR showed that ZmNTL2 was expressed in all tested tissues. ZmNTL2 functions as a transcriptional activator and is located in both the nucleus and biomembranes. The mutation does not affect the mRNA abundance of ZmNTL2 locus, but it does result in the loss of transmembrane domain and confines the ZmNTL2△ protein to the nucleus. Knocking out ZmNTL2 has no effect on maize organ size development, indicating that the 4-bp deletion might be a gain-of-function mutation in organ size regulation. Combining transcriptome sequencing with cytokinin and auxin content determination suggests that the decreased organ size may be possibly mediated by changes in hormone homeostasis. [ABSTRACT FROM AUTHOR]

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6-BA, a small molecule compound of cytokinins, has been proven to delay leaf senescence in different species, including Chinese flowering cabbage; however, its specific mechanism remains relatively unknown. In this study, the application of external 6-BA delayed leaf senescence in Chinese flowering cabbage, showing that 6-BA effectively prevented the decrease in the maximum quantum yield (Fv/Fm) and overall chlorophyll content and suppressed the expression of the senescence-associated gene BrSAG12 over a 7-day period of storage. Moreover, treatment with 6-BA decreased the respiratory rate, NAD(H) content, the activities of hexose phosphate isomerase (PHI), succinate dehydrogenase (SDH), cytochrome c oxidase (CCO), and ascorbic acid oxidase (AAO) using enzyme-linked immunosorbent assay, and the transcriptional abundance of related genes by real-time quantitative polymerase chain reaction. Furthermore, 6-BA also increased the activity and expression levels of glucose-6-phosphate dehydrogenase (G6PDH) and 6-phosphate gluconate dehydrogenase (6-PGDH). The group treated with 6-BA retained elevated levels of NADP (H), ATP, total ATPase, and nicotinamide adenine dinucleotide kinase (NADK) activity, as well as the expression of respiratory enzymes. Molecular docking indicated that 6-BA hinders the glycolysis pathway (EMP), tricarboxylic acid cycle (TCA), and cytochrome pathway (CCP), and sustains elevated levels of the pentose phosphate pathway (PPP) through interactions with the PHI, SDH, 6-PGDH, G6PDH, CCO, and AAO proteins, consequently delaying postharvest leaf senescence in Chinese flowering cabbage. [ABSTRACT FROM AUTHOR]

Plant growth regulators (PGRs) are chemical substances that imitate the functions of phytohormones to enhance the crop yield and the harvest process. Phenylurea-derived plant growth regulators are known for their excellent efficacy in promoting fruit growth, particularly in kiwifruit, grapes, and melons. Phenylurea derivatives represent one class of the highly efficient and versatile PGRs. Specifically, forchlorfenuron (CPPU, N-(2-chloro-4-pyridinyl)- N0-phenylurea) exhibits similar growth-regulating efficacy to cytokinins and has a significant impact on the plant growth and the crop yield. As a result, there is growing interest in exploring the incorporation of various phenylurea moieties into agrochemicals to enhance their regulatory properties on crops. This review aims to provide a comprehensive overview on representative synthetic approaches for phenylurea derived PGRs. Additionally, we provide our perspective on the future development in this active research field. [ABSTRACT FROM AUTHOR]

As seed precursors, ovules are fundamental organs during the plant life cycle. Decades of morphological and molecular study have allowed for the elucidation of the complex and intricate genetic network regulating ovule development. Ovule and seed number is highly dependent on the number of ovule primordia that are determined from the placenta during early pistil development. Ovule initiation is positively regulated by the plant hormones auxins, cytokinins, and brassinosteroids, as well as negatively regulated by gibberellins. Each hormone does not act independently; multiple points of hormonal crosstalk occur to coordinately regulate ovule primordia initiation. In this review, we highlight the roles of these hormones and their interactions in the genetic and hormonal network co-regulating ovule initiation in Arabidopsis. [ABSTRACT FROM AUTHOR]

Stem cells in plants and animals are the source of new tissues and organs. In plants, stem cells are maintained in the central zone (CZ) of multicellular meristems, and large shoot meristems with an increased stem cell population hold promise for enhancing yield. The mobile homeodomain transcription factor WUSCHEL (WUS) is a central regulator of stem cell function in plant shoot meristems. Despite its central importance, the factors that directly modulate WUS protein stability have been a long-standing question. Here, we show that the peptidase DA1 physically interacts with and cleaves the WUS protein, leading to its destabilization. Furthermore, our results reveal that cytokinin signaling represses the level of DA1 protein in the shoot apical meristem, thereby increasing the accumulation of WUS protein. Consistent with these observations, loss of DA1 function results in larger shoot apical meristems with an increased stem cell population and also influences cytokinin-induced enlargement of shoot apical meristem. Collectively, our findings uncover a previously unrecognized mechanism by which the repression of DA1 by cytokinin signaling stabilizes WUS, resulting in the enlarged shoot apical meristems with the increased stem cell number during plant growth and development. The transcription factor WUSCHEL is essential for stem cell function, but factors that directly modulate WUS stability are unclear. This work discovers that the peptidase DA1 cleaves and destabilizes WUS to control shoot apical meristem size. [ABSTRACT FROM AUTHOR]

Stenotrophomonas strains, which are often described as plant growth promoting (PGP) bacteria, are ubiquitous in many environments. A total of 213 genomes of strains of Stenotrophomonas were analyzed using comparative genomics to better understand the ecological roles of these bacteria in the environment. The pan-genome of the 213 strains of Stenotrophomonas consists of 27,186 gene families, including 710 core gene families, 11,039 unique genes and 15,437 accessory genes. Nearly all strains of Stenotrophomonas harbor the genes for GH3-family cellulose degradation and GH2- and GH31-family hemicellulose hydrolase, as well as intact glycolysis and tricarboxylic acid cycle pathways. These abilities suggest that the strains of this genus can easily obtain carbon and energy from the environment. The Stenotrophomonas strains can respond to oxidative stress by synthesizing catalase, superoxide dismutase, methionine sulfoxide reductase, and disulfide isomerase, as well as managing their osmotic balance by accumulating potassium and synthesizing compatible solutes, such as betaine, trehalose, glutamate, and proline. Each Stenotrophomonas strain also contains many genes for resistance to antibiotics and heavy metals. These genes that mediate stress tolerance increase the ability of Stenotrophomonas strains to survive in extreme environments. In addition, many functional genes related to attachment and plant colonization, growth promotion and biocontrol were identified. In detail, the genes associated with flagellar assembly, motility, chemotaxis and biofilm formation enable the strains of Stenotrophomonas to effectively colonize host plants. The presence of genes for phosphatesolubilization and siderophore production and the polyamine, indole-3-acetic acid, and cytokinin biosynthetic pathways confer the ability to promote plant growth. These strains can produce antimicrobial compounds, chitinases, lipases and proteases. Each Stenotrophomonas genome contained 1-9 prophages and 17-60 genomic islands, and the genes related to antibiotic and heavy metal resistance and the biosynthesis of polyamines, indole-3-acetic acid, and cytokinin may be acquired by horizontal gene transfer. This study demonstrates that strains of Stenotrophomonas are highly adaptable for different environments and have strong potential for use as plant growth-promoting bacteria. [ABSTRACT FROM AUTHOR]

Defoliation is an inevitable abiotic stress for forage and turf grasses because harvesting, grazing, and mowing are general processes for their production and management. Vegetative regrowth occurs upon defoliation, a crucial trait determining the productivity and persistence of these grasses. However, the information about the molecular regulation of this trait is limited because it is still challenging to perform molecular analyses in forage and turf grasses. Here, we used rice as a model to investigate vegetative regrowth upon defoliation at physiological and molecular levels. This study analyzed stubble and regrown leaves following periodic defoliation using two rice varieties with contrasting regrowth vigor. Vigorous regrowth was associated with maintained chlorophyll content and photosystem II performance; a restricted and promoted mRNA accumulation of sucrose synthase (SUS) I and III subfamilies, respectively; and reduced enzymatic activity of SUS. These results suggest that critical factors affecting vegetative regrowth upon defoliation are de novo carbohydrate synthesis by newly emerged leaves and proper carbohydrate management in leaves and stubble. Physiological and genetic analyses have demonstrated that the reduced sensitivity to and inhibited biosynthesis of cytokinin enhance regrowth vigor. Proper regulation of these metabolic and hormonal pathways identified in this study can lead to the development of new grass varieties with enhanced regrowth vigor following defoliation. [ABSTRACT FROM AUTHOR]

Cytokinins (CKs) and abscisic acid (ABA) play an important role in the life of both plants and pathogenic fungi. However, the role of CKs and ABA in the regulation of fungal growth, development and virulence has not been sufficiently studied. We compared the ability of two virulent isolates (SnB and Sn9MN-3A) and one avirulent isolate (Sn4VD) of the pathogenic fungus Stagonospora nodorum Berk. to synthesize three groups of hormones (CKs, ABA and auxins) and studied the effect of exogenous ABA and zeatin on the growth, sporulation and gene expression of necrotrophic effectors (NEs) and transcription factors (TFs) in them. Various isolates of S. nodorum synthesized different amounts of CKs, ABA and indoleacetic acid. Using exogenous ABA and zeatin, we proved that the effect of these hormones on the growth and sporulation of S. nodorum isolates can be opposite, depends on both the genotype of the isolate and on the concentration of the hormone and is carried out through the regulation of carbohydrate metabolism. ABA and zeatin regulated the expression of fungal TF and NE genes, but correlation analysis of these parameters showed that this effect depended on the genotype of the isolate. This study will contribute to our understanding of the role of the hormones ABA and CKs in the biology of the fungal pathogen S. nodorum. [ABSTRACT FROM AUTHOR]

Termites are widely distributed globally and serve as a valuable food source in many countries. However, information on the myriad nutritional benefits of processed termite products in African markets remain largely unexploited. This study evaluated the phytochemicals, fatty acids, amino acids, minerals, vitamins and proximate composition of the edible winged termites (Macrotermes spp.) from three major Counties of Kenya. A total of 9 flavonoids, 5 alkaloids, and 1 cytokinin were identified. The oil content varied from 33 to 46%, exhibiting significant levels of beneficial omega 3 fatty acids, such as methyl (9Z,12Z,15Z)-octadecatrienoate and methyl (5Z,8Z,11Z,14Z,17Z)-eicosapentaenoate, ranging from 82.7–95.1 to 6.3–8.1 µg/g, respectively, across the different regions. Four essential and cereal-limiting amino acids lysine (1.0–1.3 mg/g), methionine (0.08–0.1 mg/g), leucine (0.6–0.9 mg/g) and threonine (0.1–0.2 mg/g), were predominant. Moreover, termites had a rich profile of essential minerals, including iron (70.7–111.8 mg/100 g), zinc (4.4–16.2 mg/100 g) and calcium (33.1–53.0 mg/100 g), as well as vitamins A (2.4–6.4 mg/kg), C (0.6–1.9 mg/kg) and B12 (10.7–17.1 mg/kg). The crude protein (32.2–44.8%) and fat (41.2–49.1%) contents of termites from the various Counties was notably high. These findings demonstrated the promising nutrients potential of winged termites and advocate for their sustainable utilization in contemporary efficacious functional food applications to combat malnutrition. [ABSTRACT FROM AUTHOR]

The efficiency of regeneration media, based on the morpho-cytochemical response and embryogenesis gene expression of widely cultivated cotton in Indonesia (Gossypium hirsutum L.), needs to be studied further. This study's objectives are to identify the effect of 2,4-D and IBA hormones on the morphology and induction of cotton callus; to determine the effect of regeneration media on the morphology, cytochemical, and gene expression of cotton plant during embryogenesis. This study was conducted by inducing cotton callus on MS0 medium, MS Basal + 0.1 mg/L 2,4-D and MS Basal + 0.1 mg/L IBA. The best callus induction results were regenerated on the regeneration media, namely M1 (MS Vitamin + 0.01 ppm 2,4-D + 0.3 ppm IBA + 0.5 ppm Kinetin), M2 (MS Vitamin + 0.01 ppm 2,4-D + 0.5 ppm IBA + 0.5 ppm Kinetin), M3 (MS Vitamin + 0.00 ppm 2,4-D + 0.3 ppm IBA + 0.5 ppm Kinetin), and M4 (MS Vitamin + 0, 00 ppm 2,4-D + 0.5 ppm IBA + 0.5 ppm Kinetin). The embryogenesis gene expression was observed. The best morphological results for callus induction were obtained on MS Basal + 0.1 mg/L 2,4-D medium with a compact and white callus, indicates high embryogenic and regeneration ability. The highest percentage of regenerated callus parameters was found in M2 media and further confirmed by cytochemical characterization. Embryogenesis genes expressed were GhSERK1, GhSERK2, LEC, GhWUS, and GhWOX11. Other fiber-related genes GhMYB25-like, GhHD-1, and F3H were also expressed during the embryogenesis. [ABSTRACT FROM AUTHOR]

Since its first identification in the 1950s as a regulator of cell division, cytokinin has been linked to many physiological processes in plants, spanning growth and development and various responses to the environment. Studies from the last two and one-half decades have revealed the pathways underlying the biosynthesis and metabolism of cytokinin and have elucidated the mechanisms of its perception and signaling, which reflects an ancient signaling system evolved from two-component elements in bacteria. Mutants in the genes encoding elements involved in these processes have helped refine our understanding of cytokinin functions in plants. Further, recent advances have provided insight into the mechanisms of intracellular and long-distance cytokinin transport and the identification of several proteins that operate downstream of cytokinin signaling. Here, we review these processes through a historical lens, providing an overview of cytokinin metabolism, transport, signaling, and functions in higher plants. We provide an overview of cytokinin metabolism, transport, signaling, and functions in higher plants. [ABSTRACT FROM AUTHOR]

This study was aimed to establish an efficient micropropagation protocol for three popular kenaf (Hibiscus cannabinus L.) cultivars (V36, HF992 and KB6) using different types of plant growth regulators (PGR’s) on Murashige and Skoog medium (MS). The shoot tip, cotyledon and hypocotyl isolated from 2 weeks old seedlings were used as explants. MS medium fortified with different types and concentrations of cytokinins and auxin were evaluated for establishment callus formation, shoot multiplication and rooting. Among different PGR’s used, 5.0 mg/l 2iP + 0.1 mg/l NAA was the best concentration for direct shoot regeneration from cotyledon with shooting percentage of 55% in HF992 cultivar. In multiple shoot induction experiment, 1.0 mg/l TDZ + 0.1 mg/l NAA mg/l concentration has induced the highest (10.4) shoots/explant. Moreover, indirect shoot regeneration was established from callus which was induced from cotyledon, maximum callus induction percentage (88.75%) was recorded on 0.5 mg/l TDZ and 1.0 mg/l NAA in V36 variety. While, for shoot elongation and rooting, MS media half strength supplemented with 1.0 mg/l kinetin + 1.0 mg/l IBA was found to be an optimum concentration. [ABSTRACT FROM AUTHOR]

Phytohormones that trigger or repress flower meristem development in apple buds are thought to be locally emitted from adjacent plant tissues, including leaves and fruitlets. The presence of fruitlets is known to inhibit adjacent buds from forming flowers and thus fruits. The resulting absence of fruitlets the following season restores flower-promoting signalling to the new buds. The cycle can lead to a biennial bearing behaviour of alternating crop loads in a branch or tree. The hormonal stimuli that elicit flowering is typically referred to as the floral induction (FI) phase in bud meristem development. To determine the metabolic pathways activated in FI, young trees of the cultivar 'Ruby Matilda' were subjected to zonal crop load treatments imposed to two leaders of bi-axis trees in the 2020/2021 season. Buds were collected over the expected FI phase, which is within 60 DAFB. Metabolomics profiling was undertaken to determine the differentially expressed pathways and key signalling molecules associated with FI in the leader and at tree level. Pronounced metabolic differences were observed in trees and leaders with high return bloom with significant increases in compounds belonging to the cytokinin, abscisic acid (ABA), phenylpropanoid and flavanol chemical classes. The presence of cytokinins, namely adenosine, inosine and related derivatives, as well as ABA phytohormones, provides further insight into the chemical intervention opportunities for future crop load management strategies via plant growth regulators. [ABSTRACT FROM AUTHOR]

Summary: Theoretically, the PEP‐CK C4 subtype has a higher quantum yield of CO2 assimilation (ΦCO2) than NADP‐ME or NAD‐ME subtypes because ATP required for operating the CO2‐concentrating mechanism is believed to mostly come from the mitochondrial electron transport chain (mETC). However, reported ΦCO2 is not higher in PEP‐CK than in the other subtypes. We hypothesise, more photorespiration, associated with higher leakiness and O2 evolution in bundle‐sheath (BS) cells, cancels out energetic advantages in PEP‐CK species.Nine species (two to four species per subtype) were evaluated by gas exchange, chlorophyll fluorescence, and two‐photon microscopy to estimate the BS conductance (gbs) and leakiness using a biochemical model.Average gbs estimates were 2.9, 4.8, and 5.0 mmol m−2 s−1 bar−1, and leakiness values were 0.129, 0.179, and 0.180, in NADP‐ME, NAD‐ME, and PEP‐CK species, respectively. The BS CO2 level was somewhat higher, O2 level was marginally lower, and thus, photorespiratory loss was slightly lower, in NADP‐ME than in NAD‐ME and PEP‐CK species. Differences in these parameters existed among species within a subtype, and gbs was co‐determined by biochemical decarboxylating sites and anatomical characteristics.Our hypothesis and results partially explain variations in observed ΦCO2, but suggest that PEP‐CK species probably use less ATP from mETC than classically defined PEP‐CK mechanisms. [ABSTRACT FROM AUTHOR]

Introduction: Paeonia lactiflora contains diverse active constituents and exhibits various pharmacological activities. However, only partial identification of biologically active substances from P. lactiflora has been achieved using low-throughput techniques. Here, the roots of P. lactiflora, namely, Fenyunu (CK), Dafugui (DFG), and Red Charm (HSML), were studied. The primary and secondary metabolites were investigated using ultrahigh-performance liquid chromatography-electrospray ionization-tandem mass spectrometry (UPLC-ESIMS/MS). Methods: The chemical compounds and categories were detected using broadly targeted UPLC–MS/MS. Principal component analysis (PCA), orthogonal partial least-squares discriminant analysis (OPLS-DA), and hierarchical clustering analysis (HCA) were carried out for metabolites of different varieties of P. lactiflora. Results: A total of 1237 compounds were detected and classified into 11 categories. HCA, PCA, and OPLS-DA of these metabolites indicated that each variety of P. lactiflora was clearly separated from the other groups. Differential accumulated metabolite analysis revealed that the three P. lactiflora varieties contained 116 differentially activated metabolites (DAMs) involved in flavonoid, flavone, and flavonol metabolism. KEGG pathway analysis revealed that, in 65 pathways, 336 differentially abundant metabolites (DMs) were enriched in the CK and DFG groups; moreover, the type and content of terpenoids were greater in the CK group than in the DFG group. The CK and HSML groups contained 457 DMs enriched in 61 pathways; the type and amount of flavonoids, terpenoids, and tannins were greater in the CK group than in the HSML group. The DFG and HSML groups contained 497 DMs enriched in 65 pathways; terpenoids and alkaloids were more abundant in the HSML variety than in the DFG variety. Conclusions: A total of 1237 compounds were detected, and the results revealed significant differences among the three P. lactiflora varieties. Among the three P. lactiflora varieties, phenolic acids and flavonoids composed the largest and most diverse category of metabolites, and their contents varied greatly. Therefore, CK is suitable for medicinal plant varieties, and DFG and HSML are suitable for ornamental plant varieties. Twelve proanthocyanidin metabolites likely determined the differences in color among the three varieties. [ABSTRACT FROM AUTHOR]