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Abstract Cold stress poses a significant threat to the quality and productivity of lychee (Litchi chinensis Sonn.). While previous research has extensively explored the genomic and transcriptomic responses to cold stress in lychee, the translatome has not been thoroughly investigated. This study delves into the translatomic landscape of the 'Xiangjinfeng' cultivar under both control and low-temperature conditions using RNA sequencing and ribosome profiling. We uncovered a significant divergence between the transcriptomic and translatomic responses to cold exposure. Additionally, bioinformatics analyses underscored the crucial role of codon occupancy in lychee's cold tolerance mechanisms. Our findings reveal that the modulation of translation via codon occupancy is a vital strategy to abiotic stress. Specifically, the study identifies ribosome stalling, particularly at the E site AAU codon, as a key element of the translation machinery in lychee's response to cold stress. This work enhances our understanding of the molecular dynamics of lychee's reaction to cold stress and emphasizes the essential role of translational regulation in the plant's environmental adaptability.

IntroductionSalt stress severely inhibit plant growth and development. Uniconazole has been considered to significantly increase plant stress tolerance. However, the mechanism by which Uniconazole induces salt tolerance in rice seedlings and its impact on yield is still unclear.MethodsIn this study, the effects of exogenous Uniconazole on morphogenesis, physiological metabolism, and yield of rice seedlings under salt stress were analyzed using the salt-tolerant rice variety HD961 and the salt-sensitive rice variety 9311.ResultsThe results showed that salt stress significantly inhibited rice growth, disrupted the antioxidant system and pigment accumulation, and reduced photosynthesis, and yield. There were corresponding percent decreases of 13.0% and 24.1% in plant height, 31.6% and 55.8% in leaf area, 65.7% and 85.3% in root volume, respectively for HD961 and 9311. spraying However, compared to salt stress, the US treatment increased the percentage to 4.7% and 139.0% in root volume, 7.5% and 38.0% in total chlorophyll, 4.5% and 14.3% in peroxidase (POD) of leaves, 14.4% and 54.2% in POD of roots, 18.7% and 22.7% in catalase (CAT) of leaves, and 22.6% and 53.9% in CAT of roots, respectively, for HD961 and 9311. In addition, it also significantly enhanced photosynthesis at the reproductive stage, promoted the transport of carbohydrate to grains. And US treatment significantly increased the percentage to 9.0% in panicle length, 28.0% in panicle number per hole, 24.0% in filled grain number, 3.0% in 1000-grain weight, and 26.0% in yield per plant, respectively, for HD961, compared to salt stress.DiscussionIn summary, applying Uniconazole at the seedling stage can alleviate the damage induced by NaCl stress on rice by regulating the physiological metabolism of rice plants. This reduces the negative effects of salt stress, enhance salt tolerance, and boost rice production.

Soil salinity pollution is increasing worldwide, seriously affecting plant growth and crop production. Existing reports on how potassium indole-3-butyric acid (IBAK) regulates rice salt stress adaptation by affecting rice carbon metabolism, transcription factor (TF) genes expression, and biosynthesis of secondary metabolites still have limitations. In this study, an IBAK solution at 40 mg L−1 was sprayed on rice leaves at the seedling stage. The results showed that the IBAK application could promote shoot and root growth, decrease sucrose and fructose content, increase starch content, and enhance acid invertase (AI) and neutral invertase (NI) activity under salt stress, indicating altered carbon allocation. Furthermore, the expression of TF genes belonging to the ethylene responsive factor (ERF), WRKY, and basic helix-loop-helix (bHLH) families was influenced by IBAK. Many key genes (OsSSIIc, OsSHM1, and OsPPDKB) and metabolites (2-oxoglutaric acid, fumaric acid, and succinic acid) were upregulated in the carbon metabolism pathway. In addition, this study highlighted the role of IBAK in regulating the biosynthesis of secondary metabolites pathway, potentially contributing to rice stress adaptability. The results of this study can provide new sustainable development solutions for agricultural production.

IntroductionSalt stress is a major abiotic stress that affects crop growth and productivity. Choline Chloride (CC) has been shown to enhance salt tolerance in various crops, but the underlying molecular mechanisms in rice remain unclear.MethodsTo investigate the regulatory mechanism of CC-mediated salt tolerance in rice, we conducted morpho-physiological, metabolomic, and transcriptomic analyses on two rice varieties (WSY, salt-tolerant, and HHZ, salt-sensitive) treated with 500 mg·L-1 CC under 0.3% NaCl stress.ResultsOur results showed that foliar application of CC improved morpho-physiological parameters such as root traits, seedling height, seedling strength index, seedling fullness, leaf area, photosynthetic parameters, photosynthetic pigments, starch, and fructose content under salt stress, while decreasing soluble sugar, sucrose, and sucrose phosphate synthase levels. Transcriptomic analysis revealed that CC regulation combined with salt treatment induced changes in the expression of genes related to starch and sucrose metabolism, the citric acid cycle, carbon sequestration in photosynthetic organs, carbon metabolism, and photosynthetic antenna proteins in both rice varieties. Metabolomic analysis further supported these findings, indicating that photosynthesis, carbon metabolism, and carbon fixation pathways were crucial in CC-mediated salt tolerance.DiscussionThe combined transcriptomic and metabolomic data suggest that CC treatment enhances rice salt tolerance by activating distinct transcriptional cascades and phytohormone signaling, along with multiple antioxidants and unique metabolic pathways. These findings provide a basis for further understanding the mechanisms of metabolite synthesis and gene regulation induced by CC in rice in response to salt stress, and may inform strategies for improving crop resilience to salt stress.

The study of crop response to soil salinity has traditionally focused on the effects of varying salt concentrations, with less attention given to the methodologies of salt application. This research aimed to elucidate the differential impacts of two distinct salinity exposure methods on the photosynthetic characteristics of rice. Plants subjected to a gradual increase in salinity experience salt stress, whereas those immediately exposed to high salinity levels encounter a salt shock condition. Our findings revealed that rice plants accumulated comparable levels of shoot Na+ under both salt stress and salt shock at 4 and 10 days after the onset of stress. No significant differences were observed in the steady-state photosynthetic rate and electron transport rate (ETR). In contrast, salt stress markedly reduced the relative variable fluorescence at the ‘J’ step (Vj), thereby enhancing the probability of an exciton transferring an electron beyond the primary quinone electron acceptor (QA−) (ΨEo). This led to a notable increase in the activity of leaf photosystem II (PSII), as evidenced by the Performance Index on absorption basis (PIabs), which was twice as high as that of the control group. This mechanism is believed to facilitate the activation of alternative metabolic pathways. Additionally, kinetic measurements of light potential indicated that salt stress improved the initial induction of ETR after a brief exposure to high photosynthetically active radiation (PAR) compared to the control. This effect was not observed in the salt shock treatment group. Our results suggest that plants exhibit distinct physiological responses to salt stress versus salt shock, and the potential positive influence on leaf photosynthetic activity during salt stress may have been previously underestimated.

Abstract Background Salinity stress is an environmental constraint that normally develops concurrently under field conditions, resulting in drastic limitation of rice plant growth and grain productivity. The objective of this study was to explore the alleviating effects of NaCl pre-treatment on rice seedlings as well as the salt tolerance mechanisms by evaluating morph-physiological traits. Results Variety Huanghuazhan, either soaked in distilled water or 25 mg/L Prohexadione calcium (Pro-Ca), were first hardened with varying concentrations of NaCl solutions (0 and 50 mM NaCl), and then subjected to varying degrees of salt stress (0 and 100 mM NaCl), indicated by S0, S1, S2 and S3, respectively. Growth analysis suggested that NaCl-pretreatment improved the root/shoot ratio in water-soaked rice plant at DAP 0. Data related to the reaction center density, photosynthetic electron transport efficiency, trapping efficiency were compared before (CK) using performance Index (PIabs). Compared to S2 (Pro-Ca-S2) treatment, PIabs did not show any difference with plants pre-treated with NaCl (S3 or Pro-Ca-S3). Rather than PIabs, significant difference was found in photosynthetic electron transport efficiency (ΨEo). The ΨEo value in Pro-S2 was significantly lowered as compared to Pro-S3 treatment at DAP 7, and the decrease rate was about 6.5%. Correlation analysis indicated leaf PIabs was weak correlated with plant biomass while the quantum yield for reduction of the PSI end electron acceptors, trapped energy flux per reaction center and PSII antenna size displayed strong positive correlation with biomass. Additional analysis revealed that 100 mM NaCl significantly reduced leaf linear electron flux under low-light conditions, regardless of whether seedlings had been pre-treated with 50 mM NaCl or not. Conclusions NaCl-induced salt tolerance was related to the robust photosynthetic machinery.

Abstract Abscisic acid (ABA) has been shown to mitigate the deleterious effects of abiotic stresses and to regulate plant growth and development. Salinity is one of the important abiotic stresses affecting plant cell metabolism and physiology, which causes serious damages to crops. In this study, we investigated the protective role of exogenous ABA on leaves in response to salinity stress using rice seedlings (two leaf-one heart) subjected to three treatments: ZCK (control), ZS (50 mM NaCl), and ZSA (5 mg L–1 ABA + 50 mM NaCl). We carried out transcriptomic and metabolomic analyses to identify the molecular mechanisms by which ABA protects plants against salt stress. Results showed that 1159 differentially expressed genes (DEGs) (916 up-regulated, 243 down-regulated) and 63 differentially accumulated metabolites (DAMs) (42 up-regulated, 21 down-regulated) were identified between the ZS and ZSA treatments, respectively. In addition, ABA pretreatment regulated the expression pattern of genes responsible for oxidation redox, starch and sucrose metabolism, and phenylpropanoid biosynthesis. The combined transcriptomic and metabolomic analysis revealed that 16 DEGs and 2 DAMs were involved in Flavonoid biosynthesis and 8 DEGs and 2 DAMs were involved alpha-Linolenic acid metabolism which are responsible for salinity stress tolerance through induced by exogenous ABA. Overall, ABA could enhance rice leaves growth and development mainly by regulating flavonoid biosynthesis and linoleic acid metabolism pathway.

Abstract Background IBAK, as a plant growth regulator, has broad application prospects in improving crop resistance to abiotic stress. Results In this study, the regulation mechanism of IBAK on rice was revealed by physiology and transcriptomics by spraying 80 mg·L−1 IBAK solution on rice leaves at the early jointing stage under salt stress. The results showed that spraying IBAK solution on leaves under salt stress could significantly increase K+ content, decrease Na+ content, increase net photosynthetic rate (Pn), and increase the activity of catalase (CAT) and the contents of glutathione (GSH) and soluble protein in rice leaves. Using IBAK under salt stress increased the expression of plant hormone signal transduction pathway-related genes LOC4332548 and LOC4330957, which may help rice to more effectively sense and respond to plant hormone signals and enhance resistance to salt stress. In addition, the photosynthesis pathway-related genes LOC4339270, LOC4327150, and LOC4346326 were upregulated after using IBAK under salt stress, and the upregulation of these genes may be beneficial to improve the efficiency of photosynthesis and increase the photosynthetic capacity of rice. Regarding starch and sucrose metabolism pathway, spraying IBAK on leaves could promote the expression of sucrose synthesis-related gene LOC4347800 and increase the expression of starch synthesis-related genes LOC4330709 and LOC4343010 under salt stress. Finally, IBAK spraying resulted in the upregulation of multiple 50 S and 30 S ribosomal protein genes in the ribosome pathway, which may increase protein synthesis, help maintain cell function, and promote rice growth and development. Conclusion The results of this study revealed the mechanism of IBAK mediating resistance to salt stress in rice.

Salt stress is a key environmental factor altering rice plant growth. Strigolactones (GR24) play a vital role in responding to various abiotic stresses and regulating plant growth. However, the regulatory mechanisms of SLs on rice seedlings under salt stress have not yet been clarified. A pot experiment was undertaken to evaluate the effects of GR24 soaking on the rice variety ‘Huanghuazhan’ (salt-sensitive) seedling growth, antioxidant metabolism, and endogenous hormones under NaCl stress. Results showed that NaCl stress significantly inhibited rice growth; disrupted antioxidant enzymes activity; and increased the content of soluble proteins (SPs), proline (Pro), malondialdehyde (MDA) and hydrogen–peroxide (H2O2). GR24 significantly improved photosynthetic pigments and antioxidant–enzyme activities, including superoxide dismutase (SOD), catalase (CAT), peroxidase (POD), and ascorbate–peroxidase (APX); increased SP, ascorbic acid (AsA); and reduced glutathione (GSH) content and MDA, H2O2, and Pro content, resulting in the mitigation of oxidative injury caused by NaCl stress. Moreover, GR24 significantly increased the content of strigolactones (SLs), cytokinin (CTK), auxin (IAA), Gibberellin A3 (GA3), and IAA/ABA and CTK/ABA ratios and decreased the abscisic acid (ABA). Findings indicated that GR24 alleviated oxidative damage caused by NaCl stress by increasing photosynthetic and antioxidant capacity and maintaining the balance of endogenous hormones, thus improving the salt tolerance of rice seedlings.

Assessing salt tolerance in plants under field conditions is a challenging task. The objective of this research was to assess the effectiveness of different methods (leaf disc assay and pot experiment) for evaluating salt tolerance in rice. Using two varieties with different salt tolerance, Changmaogu (CM) and 9311, under three NaCl levels (0, 0.3%, and 1.0%), we evaluated the photosynthetic performance in terms of chlorophyll content in leaf disc assays, as well as the photosynthetic rate (Pn), chlorophyll content, linear electron flow (LEF), and non-photochemical quenching (NPQ), in a semi-controlled pot experiment. In the leaf disc assay, CM showed a smaller decrease in chlorophyll content compared to 9311, especially under 1.0% salinity. Simultaneously, in the pot experiment, the CM variety employed flexible photosynthetic strategies, actively decreasing LEF and Pn after 5 days of salt stress (day 5) and then increasing photosynthetic capacity (chlorophyll content, LEF, and Pn) on day 10. Notably, the total chlorophyll content for the CM variety under 1.0% salinity was significantly higher than in the control, showing a 25.0% increase. Additionally, CM demonstrated NPQt sensitivity under 0.3% salinity, requiring an LEF of 150 to achieve an NPQt value of 3.0, compared to an LEF of 180 in the control. These results suggest that a simple leaf disc assay may not fully capture the adaptive mechanisms of rice plants under salinity stress. Therefore, we advocate for the use of more comprehensive methods, such as outdoor pot or field experiments, to gain a deeper understanding and more accurate evaluation of salt tolerance in rice.

In Northeast China’s black soil rice cropping area, nitrogen (N) application is lower than in the south, yet excessive N fertilizer use persists, particularly in base fertilizers. This study aimed to assess the impact of reduced N and increased planting density on rice yields and photosynthetic matter production. From 2019 to 2020, a field split-plot experiment was conducted with two N rates (conventional N, CN: 120 kg ha−1 and reduced basal N, RN: 108 kg ha−1) and two planting densities (D1: 33.3 × 104 hills ha−1 and D2: 27.8 × 104 hills ha−1) using the rice varieties Kongyu131 (KY131) and Kendao24 (KD24). The results showed that RN increased the effective panicle formation rate but decreased the tiller numbers, dry matter accumulation, stems/sheaths transport capacity, leaf photosynthetic capacity, and yield by 2.67% compared to CN. D1 significantly boosted the dry matter accumulation, stems/sheaths transport, effective panicles, grains per square meter, and yield by 8.26% compared to D2. Interaction analysis revealed that RN under D2 conditions reduced the effective panicle percentage, harvest index, filled grain number, leaf area index (LAI), crop growth rate (CGR), and net assimilation rate (NAR) but increased the seed setting rate and 1000-grain weight. Under D1, RN reduced the LAI, CGR, and NAR at the tillering and heading stages but increased the NAR post-heading. Compared to CND2, RND1 increased the biomass, stems/sheaths transport, LAI, CGR, NAR, seed setting rate, 1000-grain weight, panicle numbers, and filled grains per square meter, compensating for the lower harvest index and effective panicle rate, achieving a 5.36% yield increase. KD24 outperformed KY131 in yield improvement. In summary, using 108 kg ha−1 with a planting density of 33.3 × 104 hills ha−1 promotes tillering, enhances photosynthetic substance production stems/sheaths dry matter transport, and increases rice yields.

Dragon fruits have abundant nutritional and antioxidant properties. High temperatures limit the growth and production of dragon fruits. Hemin can effectively alleviate abiotic stress in plants. However, the regulatory effect of Hemin on dragon fruit under heat stress remains unclear. In this study, we explored the impacts of foliar application of Hemin on dragon fruit size, yield and quality during the high temperatures of the summer season. In this experiment, dragon fruit variety ‘Jindu No. 1’ was used as material and treated with three Hemin concentrations, i.e., H1: 1 μmol.L−1, H2: 10 μmol.L−1, H3: 100 μmol.L−1, compared with CK: control. The results show that exogenous Hemin increased the single fruit weight, yield, fruit shape index and edible rate. It also improved pericarp L* value, a* value, C* and decreased ho, improving the peel colour; exogenous Hemin enhanced soluble solids content and phenolic compounds content and antioxidant enzyme activities in the pulp of dragon fruit. In addition, exogenous Hemin increased the content of chlorophyll content in dragon fruit stems. Differential metabolites determined by metabolomic assay also indicated that Hemin significantly increased the content of active substances such as selagin. Additionally, the Hemin treatment H2 also activated the activity of antioxidant enzymes such as superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), and ascorbate peroxidase (APX), which helps to mitigate the effects of high temperatures on dragon fruit. The current findings strongly advocate that H2 treatment may effectively counteract the adverse effects of heat stress by regulating the morph-physiological and antioxidant traits.

Salinity stress imposes severe constraints on plant growth and development. Here, we explored the impacts of prohexadione-calcium (Pro-Ca) on rapeseed growth under salt stress. We designed a randomized block design pot experiment using two rapeseed varieties, ‘Huayouza 158R’ and ‘Huayouza 62’. We conducted six treatments, S0: non-primed + 0 mM NaCl, Pro-Ca+S0: Pro-Ca primed + 0 mM NaCl, S100: non-primed + 100 mM NaCl, Pro-Ca+S100: Pro-Ca primed + 100 mM NaCl, S150: non-primed + 150 mM NaCl, Pro-Ca+S150: Pro-Ca primed + 150 mM NaCl. The morphophysiological characteristics, and osmoregulatory and antioxidant activities were compared for primed and non-primed varieties. Our data analysis showed that salt stress induced morph-physiological traits and significantly reduced the antioxidant enzyme activities in both rapeseed varieties. The Pro-Ca primed treatment significantly improved seedlings, root, and shoot morphological traits and accumulated more dry matter biomass under salt stress. Compared to Huayouza 158R, Huayouza 62 performed better with the Pro-Ca primed treatment. The Pro-Ca primed treatment significantly enhanced chlorophyll content, net photosynthetic rate (Pn), stomatal conductance (Gs), transpiration rate (Tr), and actual photochemical quantum efficiency (ФPSII). Furthermore, the Pro-Ca primed treatment also improved ascorbic acid (ASA) content, superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), and ascorbate peroxidase (APX) activity, and stimulated the accumulation of soluble proteins. These findings strongly suggested that the Pro-Ca primed treatment may effectively counteract the negative impacts of salinity stress by regulating the morph-physiological and antioxidant traits.

Abiotic stress caused by soil salinization remains a major global challenge that threatens and severely impacts crop growth, causing yield reduction worldwide. In this study, we aim to investigate the damage of salt stress on the leaf physiology of two varieties of rice (Huanghuazhan, HHZ, and Xiangliangyou900, XLY900) and the regulatory mechanism of Hemin to maintain seedling growth under the imposed stress. Rice leaves were sprayed with 5.0 μmol·L−1 Hemin or 25.0 μmol·L−1 ZnPP (Zinc protoporphyrin IX) at the three leaf and one heart stage, followed by an imposed salt stress treatment regime (50.0 mmol·L−1 sodium chloride (NaCl)). The findings revealed that NaCl stress increased antioxidant enzymes activities and decreased the content of nonenzymatic antioxidants such as ascorbate (AsA) and glutathione (GSH). Furthermore, the content of osmoregulatory substances like soluble proteins and proline was raised. Moreover, salt stress increased reactive oxygen species (ROS) content in the leaves of the two varieties. However, spraying with Hemin increased the activities of antioxidants such as superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT) and accelerated AsA-GSH cycling to remove excess ROS. In summary, Hemin reduced the effect of salt stress on the physiological characteristics of rice leaves due to improved antioxidant defense mechanisms that impeded lipid peroxidation. Thus, Hemin was demonstrated to lessen the damage caused by salt stress.

The aim of this experiment was to investigate the effects of exogenous sprays of 5-aminolevulinic acid (5-ALA) and 2-Diethylaminoethyl hexanoate (DTA-6) on the growth and salt tolerance of rice (Oryza sativa L.) seedlings. This study was conducted in a solar greenhouse at Guangdong Ocean University, where ‘Huanghuazhan’ was selected as the test material, and 40 mg/L 5-ALA and 30 mg/L DTA-6 were applied as foliar sprays at the three-leaf-one-heart stage of rice, followed by treatment with 0.3% NaCl (W/W) 24 h later. A total of six treatments were set up as follows: (1) CK: control, (2) A: 40 mg⋅ L−1 5-ALA, (3) D: 30 mg⋅ L−1 DTA-6, (4) S: 0.3% NaCl, (5) AS: 40 mg⋅ L−1 5-ALA + 0.3% NaCl, and (6) DS: 30 mg⋅ L−1 DTA-6+0.3% NaCl. Samples were taken at 1, 4, 7, 10, and 13 d after NaCl treatment to determine the morphology and physiological and biochemical indices of rice roots. The results showed that NaCl stress significantly inhibited rice growth; disrupted the antioxidant system; increased the rates of malondialdehyde, hydrogen peroxide, and superoxide anion production; and affected the content of related hormones. Malondialdehyde content, hydrogen peroxide content, and superoxide anion production rate significantly increased from 12.57% to 21.82%, 18.12% to 63.10%, and 7.17% to 56.20%, respectively, in the S treatment group compared to the CK group. Under salt stress, foliar sprays of both 5-ALA and DTA-6 increased antioxidant enzyme activities and osmoregulatory substance content; expanded non-enzymatic antioxidant AsA and GSH content; reduced reactive oxygen species (ROS) accumulation; lowered malondialdehyde content; increased endogenous hormones GA3, JA, IAA, SA, and ZR content; and lowered ABA content in the rice root system. The MDA, H2O2, and O2− contents were reduced from 35.64% to 56.92%, 22.30% to 53.47%, and 7.06% to 20.01%, respectively, in the AS treatment group compared with the S treatment group. In the DS treatment group, the MDA, H2O2, and O2− contents were reduced from 24.60% to 51.09%, 12.14% to 59.05%, and 12.70% to 45.20%. In summary, NaCl stress exerted an inhibitory effect on the rice root system, both foliar sprays of 5-ALA and DTA-6 alleviated damage from NaCl stress on the rice root system, and the effect of 5-ALA was better than that of DTA-6.

Soybean (Glycine max) and mung bean (Vigna radiata) are key legumes with global importance, but their mechanisms for coping with cold stress—a major challenge in agriculture—have not been thoroughly investigated, especially in a comparative study. This research aimed to fill this gap by examining how these two major legumes respond differently to cold stress and exploring the role of uniconazole, a potential stress mitigator. Our comprehensive approach involved transcriptomic and metabolomic analyses, revealing distinct responses between soybean and mung bean under cold stress conditions. Notably, uniconazole was found to significantly enhance cold tolerance in mung bean by upregulating genes associated with photosynthesis, while its impact on soybean was either negligible or adverse. To further understand the molecular interactions, we utilized advanced machine learning algorithms for protein structure prediction, focusing on photosynthetic pathways. This enabled us to identify LOC106780309 as a direct binding target for uniconazole, confirmed through isothermal titration calorimetry. This research establishes a new comparative approach to explore how soybean and mung bean adapt to cold stress, offers key insights to improve the hardiness of legumes against environmental challenges, and contributes to sustainable agricultural practices and food security.

Prohexadione calcium (EA) and gibberellin (GA) are two different types of plant growth regulators that have different effects on the regulation of plant development. The objective of this study was to evaluate the impacts of EA and GA on rice plant growth, development and morph-physiological traits in two rice varieties: ‘Huang Huazhan’ and ‘Guang Hong 3’. At the three-leaf seedling stage, the plants were treated with 50 mM NaCl 24 h after foliar application of EA (100 mg·L−1) and GA (1 mg·L−1). Data on morphological indexes, osmotic regulators and antioxidant activities were compared with the treatment of EA and GA on the 4th, 7th, 10th and 13th days after NaCl stress. Our data analysis showed that NaCl stress inhibited the leaf area growth of rice seedlings, altered the microstructure and disrupted the antioxidant system, ion uptake and transport balance. The significant increase in malondialdehyde (MDA) content and superoxide anion production rate (O2·¯) indicated that NaCl stress caused a severe oxidative stress response to rice seedlings. Treatment with EA and GA activated the antioxidant system under NaCl stress, significantly elevated superoxide dismutase (SOD), peroxidase (POD) and catalase (CAT) activities and suppressed the increase in MDA content and the O2·¯ production rate. Under NaCl stress, EA and GA treatments improved the osmoregulatory balance, significantly increased soluble protein and proline contents and maintained lower Na+/K+ levels. EA and GA treatments significantly increased the K+ and Ca2+ contents, thereby maintaining ionic balance, which was favorable for maintaining the growth of rice seedlings. In this study, moth plant growth regulators maintained the growth and development of rice seedlings under NaCl stress by inducing an increase in osmoregulation and antioxidant levels, reducing the degree of membrane damage and regulating the selective uptake of ions by rice seedlings. Current findings also clarified that foliar application of EA was more effective than GA in three-leaf seedlings by enhancing the morph-physiological and antioxidant parameters under NaCl stress.

With the increasingly severe problem of soil salinization worldwide, exploring the molecular mechanism of salt tolerance of super hybrid rice has become an important scientific issue. In this study, the super hybrid rice Chaoyou1000 was used as the focus of attention, and the conventional rice Huanghuazhan was used as the control to explore the molecular mechanism of salt tolerance in super hybrid rice. The joint analysis of transcriptome and metabolome found 4661 DEGs, of which 2130 were up-regulated and 2531 were down-regulated; 70 named differential metabolites were found in the positive ion mode, and 32 were found in the negative ion mode. KEGG enrichment analysis showed that the carbohydrate metabolism-related pathways enriched by DEGs and differential metabolites were “starch and sucrose metabolism”, “galactose metabolism”, “glyoxylate and dicarboxylate metabolism”, and “citrate cycle (TCA cycle)”. Specifically, we found that some critical genes involved in carbohydrate metabolism, such as LOC4330753, LOC4325448, and LOC4341069, were up-regulated; some key metabolites, such as cis-aconitate, sucrose, and raffinose, were up-regulated. The difference in the expressions of these critical genes and metabolites between the two varieties is one of the most important reasons for the high resistance of Chaoyou1000. In addition, this study found that a large number of DEGs had a strong correlation with D-pipecolic acid, niveusin C, Gly-Val Ala-Ile, 2-(3-hydroxyphenyl)ethanol 1′-glucoside, 2,6-dimethyl-7-octene-1,6-diol 8-O-glucoside, (+)-syringaresinol, 2-indanone, 2-keto-6-acetamidocaproate, 3-dehydroquinate, IRETOL, and estrone glucuronide, suggesting that these genes and corresponding metabolites may exist with functional associations and regulatory relationships. The results of this study will provide a reference for the breeding of salt-tolerant rice.

Abstract Background Due to global warming, drought climates frequently occur on land, and despite being drought resistant, pineapples are still subjected to varying degrees of drought stress. Plant growth regulators can regulate the stress tolerance of plants through hormonal effects. This experiment aims to investigate the regulatory effects of different plant growth regulators on Tainong- 16 and MD-2 Pineapple when subjected to drought stress. Results In this experiment, we examined the regulatory effects of two different plant growth regulators, sprayed on two pineapple varieties: MD-2 Pineapple and Tainong-16. The main component of T1 was diethyl aminoethyl hexanoate (DA-6) and that of T2 is chitosan oligosaccharide (COS). An environment similar to a natural drought was simulated in the drought stress treatments. Then, pineapples at different periods were sampled and a series of indicators were measured. The experimental results showed that the drought treatments treated with T1 and T2 plant growth regulators had a decrease in malondialdehyde, an increase in bromelain and antioxidant enzyme indicators, and an increase in phenotypic and yield indicators. Conclusion This experiment demonstrated that DA-6 and COS can enhance the drought resistance of pineapple plants to a certain extent through bromelain and oxidative stress. Therefore, DA-6 and COS have potential applications and this experiment lays the foundation for further research.

Abstract It is widely known that salt stress restricts rice growth and productivity severely. However, little information is available regarding the stage of rice seedlings subjected to the Heme oxygenase 1 (HO-1) inducer, Hemin. This study aimed to investigate the effects of salt stress on two rice varieties (Huanghuazhan and Xiangliangyou 900) and the effect of Hemin in promoting photosynthesis, carbohydrate metabolism, and key enzymes under salt-stress conditions. At the stage of three leaves and one heart, Huanghuazhan (HHZ) and Xiangliangyou 900 (XLY900) were sprayed with 5 μmol·L−1 Hemin and then subjected to 50 mM NaCl stress. The results showed that NaCl stress decreased the contents of chlorophyll a, chlorophyll b, and carotenoids. Furthermore, the net photosynthetic rate (P n) decreased remarkably and the starch content was also lowered. However, NaCl treatment enhanced the concentration of sucrose and soluble sugar, simultaneously enhancing the sucrose metabolism. Nevertheless, the foliar spraying of exogenous Hemin mediated the increase in fructose and starch content, along with the activities of key enzymes’ soluble acid invertase (SAInv), basic/neutral invertase (A/N-Inv), and sucrose synthase (SS) in rice leaves under NaCl stress. The sucrose phosphate synthase (SPS) in leaves decreased significantly, and the fructose accumulation in leaves increased. Hemin also mediated the increase of starch content and the α-amylase, total amylase, and starch phosphorylase (SP) activities under NaCl stress. Under stress conditions, the application of the Heme oxygenase 1 (HO-1) inhibitor, ZnPP failed to alleviate the damage to rice seedlings by NaCl stress. The ZnPP treatment showed similar tendency to the NaCl treatment on pigment content, gas exchange parameters and carbon metabolism related products and enzymes. However, ZnPP decreased carotenoids, fructose, starch content and enzyme activities related to starch metabolism. The regulation effect of Hemin on HuangHuaZhan was better than XiangLiangYou 900. These results indicate that Hemin improved the effects of salt stress on the photosynthesis and physiological characteristics of rice leaves as a result of enhanced carbohydrate metabolism. Thus, Hemin could alleviate the damage caused by salt stress to a certain extent.

Salt stress is one of the major abiotic stresses that damage the structure and composition of cell walls. Alginate oligosaccharides (AOS) have been advocated to significantly improve plant stress tolerance. The metabolic mechanism by which AOS induces salt tolerance in rice cell walls remains unclear. Here, we report the impact of AOS foliar application on the cell wall composition of rice seedlings using the salt-tolerant rice variety FL478 and the salt-sensitive variety IR29. Data revealed that salt stress decreased biomass, stem basal width, stem breaking strength, and lodging resistance; however, it increased cell wall thickness. In leaves, exogenous AOS up-regulated the expression level of OSCESA8, increased abscisic acid (ABA) and brassinosteroids (BR) content, and increased β-galacturonic activity, polygalacturonase activity, xylanase activity, laccase activity, biomass, and cellulose content. Moreover, AOS down-regulated the expression levels of OSMYB46 and OSIRX10 and decreased cell wall hemicellulose, pectin, and lignin content to maintain cell wall stability under salt stress. In stems, AOS increased phenylalamine ammonia-lyase and tyrosine ammonia-lyase activities, while decreasing cellulase, laccase, and β-glucanase activities. Furthermore, AOS improved the biomass and stem basal width and also enhanced the cellulose, pectin, and lignin content of the stem, As a result, increased resistance to stem breakage strength and alleviated salt stress-induced damage, thus enhancing the lodging resistance. Under salt stress, AOS regulates phytohormones and modifies cellulose, hemicellulose, lignin, and pectin metabolism to maintain cell wall structure and improve stem resistance to lodging. This study aims to alleviate salt stress damage to rice cell walls, enhance resistance to lodging, and improve salt tolerance in rice by exogenous application of AOS.

Rice (Oryza sativa L.), a crucial food crop that sustains over half the world’s population, is often hindered by salt stress during various growth stages, ultimately causing a decrease in yield. However, the specific mechanism of rice roots’ response to salt stress remains largely unknown. In this study, transcriptomics and lipidomics were used to analyze the changes in the lipid metabolism and gene expression profiles of rice roots in response to salt stress. The results showed that salt stress significantly inhibited rice roots’ growth and increased the roots’ MDA content. Furthermore, 1286 differentially expressed genes including 526 upregulated and 760 downregulated, were identified as responding to salt stress in rice roots. The lipidomic analysis revealed that the composition and unsaturation of membrane lipids were significantly altered. In total, 249 lipid molecules were differentially accumulated in rice roots as a response to salt stress. And most of the major phospholipids, such as phosphatidic acid (PA), phosphatidylcholine (PC), and phosphatidylserine (PS), as well as major sphingolipids including ceramide (Cer), phytoceramide (CerP), monohexose ceramide (Hex1Cer), and sphingosine (SPH), were significantly increased, while the triglyceride (TG) molecules decreased. These results suggested that rice roots mitigate salt stress by altering the fluidity and integrity of cell membranes. This study enhances our comprehension of salt stress, offering valuable insights into changes in the lipids and adaptive lipid remodeling in rice’s response to salt stress.

In order to explore the regulating role and the physiological and biochemical mechanisms of trans-abscisic acid (hereinafter referred as S-ABA) in the process of rice growth and development under salt stress, we took Chaoyou 1000 and Yuxiangyouzhan as materials and set up three salt concentration treatments, CK0 (Control treatment), N1 (50 mmol L−1 NaCl), and N2 (100 mmol L−1 NaCl), in potted trials; we aimed to study the mechanism of rice’s response to salt stress from the perspective of agricultural traits and physiological biochemicals and to improve rice’s resistance to salt stress through exogenously applying the regulating technology of S-ABA. The following results were obtained: Under salt stress, the growth of rice was significantly suppressed compared to CK0, exhibiting notable increases in agricultural indicators, photosynthesis efficiency, and the NA+ content of leaves. However, we noted a significant decrease in the K+ content in the leaves, alongside a prominent increase in NA+/K+ and a big increase in MDA (malondialdehyde), H2O2 (hydrogen peroxide), and O2− (superoxide anion). This caused the cytomembrane permeability to deteriorate. By applying S-ABA under salt stress (in comparison with salt treatment), we promoted improvements in agronomic traits, enhanced photosynthesis, reduced the accumulation of NA+ in leaves, increased the K+ content and the activity of antioxidant enzymes, and reduced the active oxygen content, resulting in a sharp decrease in the impact of salt stress on rice’s development. The application of S-ABA decreased the endogenous ABA (abscisic acid) content under salt stress treatment but increased the endogenous GA (gibberellin) and IAA (indole acetic acid) contents and maintained the hormonal homeostasis in rice plants. To summarize, salt stress causes damage to rice growth, and the exogenous application of S-ABA can activate the pouring system mechanism of rice, suppress the outbreak of active oxygen, and regulate NA+/K+ balance and hormone homeostasis in the blades, thus relieving the salt stress.

A large number of dead seedlings can occur in saline soils, which seriously affects the large-scale cultivation of rice. This study investigated the effects of plant growth regulators (PGRs) and nitrogen application on seedling growth and salt tolerance (Oryza sativa L.), which is of great significance for agricultural production practices. A conventional rice variety, “Huang Huazhan”, was selected for this study. Non-salt stress treatments included 0% NaCl (CK treatment), CK + 0.05 g N/pot (N treatment), CK + 40 mg·L−1 5-aminolevulinic acid (5-ALA) (A treatment), and CK + 30 mg·L−1 diethylaminoethyl acetate (DTA-6) (D treatment). Salt stress treatments included 0.3% NaCl (S treatment), N + 0.3% NaCl (NS treatment), A + 0.3% NaCl (AS treatment), and D + 0.3% NaCl (DS treatment). When 3 leaves and 1 heart emerged from the soil, plants were sprayed with DTA-6 and 5-ALA, followed by the application of 0.3% NaCl (w/w) to the soil after 24 h. Seedling morphology and photosynthetic indices, as well as carbohydrate metabolism and key enzyme activities, were determined for each treatment. Our results showed that N, A, and D treatments promoted seedling growth, photosynthesis, carbohydrate levels, and the activities of key enzymes involved in carbon metabolism when compared to the CK treatment. The A treatment had the most significant effect, with increases in aboveground dry weight and net photosynthetic rates (Pn) ranging from 17.74% to 41.02% and 3.61% to 32.60%, respectively. Stomatal limiting values (Ls) significantly decreased from 19.17% to 43.02%. Salt stress significantly inhibited seedling growth. NS, AS, and DS treatments alleviated the morphological and physiological damage of salt stress on seedlings when compared to the S treatment. The AS treatment was the most effective in improving seedling morphology, promoting photosynthesis, increasing carbohydrate levels, and key enzyme activities. After AS treatment, increases in aboveground dry weight, net photosynthetic rate, soluble sugar content, total sucrose synthase, and amylase activities were 17.50% to 50.79%, 11.39% to 98.10%, 20.20% to 80.85%, 21.21% to 33.53%, and 22.17% to 34.19%, respectively, when compared to the S treatment. In summary, foliar sprays of 5-ALA, DTA-6, and additional nitrogen fertilizer enhanced rice seedling growth, increased photosynthesis, lowered Ls values, and improved seedling salt tolerance. Spraying two regulators, 5-ALA and DTA-6, quantitatively increased the effect of nitrogen fertilizer, with comparable effects on NaCl stress regulation. This study provides the basis for efficient agricultural production.

Abstract The clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR‐associated protein 9 (Cas9) system is a fast‐growing, genome editing technology that has wide applications in identifying gene functions as well as improving agricultural production and crop breeding. Here, we summarized recent advances in the development and applications of genome editing technologies in plants. We briefly described CRISPR/Cas9 technology and examined the base and prime editing techniques that have been developed from CRISPR technology. Some new prime editing‐derived techniques were assessed.

This study aimed to investigate whether presoaking with hemin (5 μmol·L−1) could alleviate NaCl stress during rapeseed seedlings’ growth and its role in the regulation of photosynthesis. In this experiment, ‘HUAYOUZA 62 (HYZ 62)’ and ‘HUAYOUZA 158R (158R)’ were used as materials for pot experiments to study the morphology, photosynthetic characteristics, antioxidant activity, and osmoregulatory factors of seedlings under different salt concentrations, as well as the regulatory effects of hemin-presoaked seeds. Our findings revealed that, compared the control, NaCl stress inhibited the growth of two rapeseed varieties, decreased the seedling emergence rate, and increased the content of malondialdehyde (MDA), the electrolyte leakage rate (EL) and antioxidant enzyme activity. Hemin soaking alleviated the adverse effects of salt stress and increased plant height, root elongation and dry matter accumulation. Compared with all NaCl treatments, hemin significantly enhanced photosynthetic indexes, including a percent increase of 12.99–24.36% and 5.39–16.52% in net photosynthetic rate (Pn), 17.86–48.08% and 8.6–23.44% in stomatal conductivity (Gs), and 15.42–37.94% and 11.09–19.08% in transpiration rate (Tr) for HYZ62 and 158R, respectively. Moreover, hemin soaking also increased antioxidant enzyme activities, including superoxide dismutase (SOD), catalase (CAT), peroxidase (POD), and ascorbate peroxidase (APX), reducing the malondialdehyde, and thus resulting in the alleviation of oxidative damage caused by NaCl stress. Furthermore, hemin stimulated the formation of soluble protein, which effectively regulated the osmo-protective qualities. The current findings strongly elucidate that hemin soaking could effectively alleviate the negative impacts of NaCl stress by regulating the morphological, photosynthetic, and antioxidant traits. This study provides a new idea regarding the effect of Hemin on the salt tolerance of rapeseed, and provides a basis for the practical application of Hemin in saline–alkali soil to improve the salt tolerance of cultivated rapeseed.

Abstract Abscisic acid (ABA) plays a crucial role in response to abiotic stress as important small molecules in regulating metabolism. This study aimed to evaluate the ability of foliar spraying ABA to regulate growth quality at rice seedling stage under salt stress. Results demonstrated that salt stress strongly reduced all the growth parameters of two rice seedlings (‘Chaoyouqianhao’ and ‘Huanghuazhan’), caused prominent decrease in the levels of photosynthetic pigments (mainly in Huanghuazhan), photosynthesis and fluorescence parameters. Salinity treatment increased the concentration of malondialdehyde (MDA) and hydrogen peroxide (H2O2) in roots, whereas significant decreased H2O2 was found in leaves of Huanghuazhan. Additionally, salinity triggered high Na+ content particularly in leaves and enhanced catalase (CAT) activities, ascorbate peroxidase (APX) and peroxidase (POD) activities of the two rice seedlings. Nevertheless, salinity-induced increased root ascorbic acid (AsA) and glutathione (GSH) levels while decreased in leaves, which depended on treatment time. Conversely, ABA application partially or completely mitigated salinity toxicity on the seedlings. ABA could reverse most of the changed physiological parameters triggered by salt stress. Specially, ABA treatment improved antioxidant enzyme levels and significantly reduced the Na+ content of two varieties as well as increased the K+, Mg2+ and Ca2+ content in leaves and roots. ABA treatment increased the hormone contents of 1-aminocclopropane carboxylic acid (ACC), trans-zeatin (TZ), N6-isopentyladenosine (IPA), Indole-3-acetic acid (IAA), and ABA in leaves of two rice varieties under salt stress. It is suggested that ABA was beneficial to protect membrane lipid peroxidation, the modulation of antioxidant defense systems and endogenous hormonal balance with imposition to salt stress.

Salt stress affects crop quality and reduces crop yields, and growth regulators enhance salt tolerance of crop plants. In this report, we examined the effects of prohexadione-calcium (Pro-Ca) on improving rice (Oryza sativa L.) growth and tillering under salt stress. We found that NaCl stress inhibited the growth of two rice varieties and increased malondialdehyde (MDA) levels, electrolyte leakage, and the activities of the antioxidant enzymes. Foliar application of Pro-Ca reduced seedling height and increased stem base width and lodging resistance of rice. Further analyses showed that Pro-Ca application reduced MDA content, electrolyte leakage, and membrane damage in rice leaves under NaCl stress. Pro-Ca enhanced the net photosynthetic rate (Pn), stomatal conductance (Gs), and intercellular CO2 concentration (Ci) of rice seedlings, while increasing the activities of superoxide dismutase (SOD), catalase (CAT), peroxidase (POD), and ascorbic acid peroxidase (APX) at the tillering stage under salt stress. Overall, Pro-Ca improves salt tolerance of rice seedlings at the tillering stage by enhancing lodging resistance, reducing membrane damages, and enhancing photosynthesis and antioxidant capacities of rice seedlings.

Abstract Pulsed amplitude modulation (PAM) chlorophyll a fluorescence provides information about photosynthetic energy transduction. When reliably measured, chlorophyll a fluorescence provides detailed information about critical in vivo photosynthetic processes. Such information has recently provided novel and critical insights into how the yield potential of crops can be improved and it is being used to understand remotely sensed fluorescence, which is termed solar‐induced fluorescence and will be solely measured by a satellite scheduled to be launched this year. While PAM chlorophyll a fluorometers measure fluorescence intensity per se, herein we articulate the axiomatic criteria by which instrumentally detected intensities can be assumed to assess fluorescence yield, a phenomenon quite different than fluorescence intensity and one that provides critical insight about how solar energy is variably partitioned into the biosphere. An integrated mathematical, phenomenological, and practical discussion of many useful chlorophyll a fluorescence parameters is presented. We draw attention to, and provide examples of, potential uncertainties that can result from incorrect methodological practices and potentially problematic instrumental design features. Fundamentals of fluorescence measurements are discussed, including the major assumptions underlying the signals and the methodological caveats about taking measurements during both dark‐ and light‐adapted conditions. Key fluorescence parameters are discussed in the context of recent applications under environmental stress. Nuanced information that can be gleaned from intra‐comparisons of fluorescence‐derived parameters and intercomparisons of fluorescence‐derived parameters with those based on other techniques is elucidated.

Abstract Background Chilling injury of mung bean (Vigna radiata (L.)) during the blooming and podding stages is a major agricultural threat in Northeast China. Uniconazole (UNZ) can alleviate water deficit stress in soybean and waterlogging stress in mung bean. However, there has been no report on the effect of UNZ application on the growth and transcriptomic profile of mung bean under chilling stress. Results UNZ application before chilling stress at the R1 stage alleviated the decline in mung bean yield. UNZ delayed the decrease in leaf chlorophyll content under chilling stress at the R1 stage and accelerated the increase in leaf chlorophyll content during the recovery period. Eighteen separate RNA-Seq libraries were generated from RNA samples collected from leaves exposed to six different treatment schemes. The numbers of DEGs specific for UNZ treatment between D1 + S vs. D1 and D4 + S vs. D4 were 708 and 810, respectively. GO annotations showed that photosynthesis genes were obviously enriched among the genes affected by chilling stress and UNZ application. KEGG pathway enrichment analysis indicated that 4 pathways (cutin, suberin and wax biosynthesis; photosynthesis; porphyrin and chlorophyll metabolism; and ribosome) were downregulated, while plant–pathogen interaction was upregulated, by chilling stress. UNZ application effectively prevented the further downregulation of the gene expression of members of these 4 KEGG pathways under chilling stress. Conclusions UNZ application effectively delayed the decrease in photosynthetic pigment content under chilling stress and accelerated the increase in photosynthetic pigment content during the recovery period, thus effectively limiting the decline in mung bean yield. UNZ application effectively prevented the further downregulation of the gene expression of members of 4 KEGG pathways under chilling stress and increased mung bean tolerance to chilling stress.

Prohexadione-calcium (Pro-Ca) has been proved to play an important role in releasing abiotic stress in plants. However, there is still a lack of research on the mechanism of Pro-Ca alleviating salt stress in rice. To explore the protective effects of Pro-Ca on rice seedlings under salt stress, we investigated the effect of exogenous Pro-Ca on rice seedling under salt stress by conducting the following three treatment experiments: CK (control), S (50 mmol·L-1 NaCl saline solution) and S + Pro-Ca (50 mmol·L-1 NaCl saline solution + 100 mg·L-1 Pro-Ca). The results indicated that Pro-Ca modulated the expression of antioxidant enzyme-related genes (such as SOD2, PXMP2, MPV17, E1.11.1.7). Spraying Pro-Ca under salt stress significantly increased in ascorbate peroxidase, superoxide dismutase, and peroxidase activity by 84.2%, 75.2%, and 3.5% as compared to the salt treatment, as demonstrated by an example of a 24-hour treatment. Malondialdehyde level in Pro-Ca was also dramatically decreased by 5.8%. Moreover, spraying Pro-Ca under salt stress regulated the expression of photosynthesis genes (such as PsbS, PsbD) and chlorophyll metabolism genes (heml, PPD). Compared to salt stress treatment, spraying Pro-Ca under salt stress significantly increased in net photosynthetic rate by 167.2%. In addition, when rice shoots were sprayed with Pro-Ca under salt stress, the Na+ concentration was considerably reduced by 17.1% compared to salt treatment. In conclusion, Pro-Ca regulates antioxidant mechanisms and photosynthesis to aid in the growth of rice seedlings under salt stress.

Salt stress, as a principal abiotic stress, harms the growth and metabolism of rice, thus affecting its yield and quality. The tillering stage is the key growth period that controls rice yield. Prohexadione-calcium (Pro-Ca) can increase the lodging resistance of plants by reducing plant height, but its effects on rice leaves and roots at the tillering stage under salt stress are still unclear. This study aimed to evaluate the ability of foliar spraying of Pro-Ca to regulate growth quality at the rice tillering stage under salt stress. The results showed that salt stress reduced the tillering ability of the rice and the antioxidant enzyme activity in the roots. Salt stress also reduced the net photosynthetic rate (Pn), stomatal conductance (Gs) and intercellular CO2 concentration (Ci) of the rice leaves and increased the contents of osmotic regulatory substances in the leaves and roots. The application of exogenous Pro-Ca onto the leaves increased the tiller number of the rice under salt stress and significantly increased the photosynthetic capacity of the leaves. Additionally, it increased the activities of antioxidant enzymes and the AsA content. The contents of an osmotic regulation substance, malondialdehyde (MDA), and H2O2 in the leaves and roots also decreased. These results suggested that Pro-Ca can increase the tillering ability, photosynthetic capacity, osmotic adjustment substance content levels and antioxidant enzyme activity levels in rice and reduce membrane lipid peroxidation, thus improving the salt tolerance of rice at the tillering stage.

Prohexadione calcium (Pro-Ca), as a growth retardant, can effectively alleviate the damage of salt stress to plants. In order to explore the effects of NaCl stress on the physiological characteristics and panicle traits of rice plants as well as the alleviating effect of Pro-Ca at the booting stage, we performed pot experiments on two rice cultivars: conventional rice ‘Huanghuazhan’ and hybrid rice ‘Xiangliangyou900’. Rice plants were treated with 0.3% NaCl 48 hours after Pro-Ca (100 mg L−1) treatment to study the effects of Pro-Ca on the physiological characteristics of the leaves and panicles, as well as the panicle and yield traits of rice under salt stress. Our analysis indicated that NaCl treatment inhibited the morphological growth parameters and photosynthetic efficiency, destroyed the antioxidant defense systems of leaves and panicles, increased soluble protein and proline in both rice cultivars. Foliar application of Pro-Ca significantly increased the leaf area, uppermost internode length, panicle length, panicle weight, number of primary branches, number of grains per panicle, seed setting rate and yield under salt stress. Pro-Ca application significantly affected chlorophyll content, net photosynthetic rate (Pn), stomatal conductance (Gs), transpiration rate (Tr), and apparent mesophyll conductance (AMC) in NaCl-treated rice cultivars compared with NaCl treatment alone. Moreover, Pro-Ca also increased ascorbic acid (AsA) content, enhanced superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), and ascorbate peroxidase (APX) activity, and further increased the accumulation of soluble protein and proline in leaves and panicles. These results illustrated that foliar application of Pro-Ca at the booting stage could alleviate the damage caused by NaCl stress by regulating the physiological and metabolic processes of rice plants, thereby enhancing the stress resistance of the plants, increasing total rice yield in salt stress conditions.

Abstract Uniconazole (S-(+)-uniconazole), a plant growth retardant, exerts key roles in modulating growth and development and increasing abiotic stress tolerance in plants. However, the underlying mechanisms by which uniconazole regulates drought response remain largely unknown. Here, the effects of exogenous uniconazole on drought tolerance in hemp were studied via physiological and transcriptome analyses of the drought-sensitive industrial hemp cultivar Hanma No. 2 grown under drought stress. Exogenous uniconazole treatment increased hemp tolerance to drought-induced damage by enhancing chlorophyll content and photosynthesis capacity, regulating activities of enzymes involved in carbon and nitrogen metabolism, and altering endogenous hormone levels. Expression of genes associated with porphyrin and chlorophyll metabolism, photosynthesis-antenna proteins, photosynthesis, starch and sucrose metabolism, nitrogen metabolism, and plant hormone signal transduction were significantly regulated by uniconazole compared with that by control (distilled water) under drought stress. Numerous genes were differentially expressed to increase chlorophyll content, enhance photosynthesis, regulate carbon–nitrogen metabolism-related enzyme activities, and alter endogenous hormone levels. Thus, uniconazole regulated physiological and molecular characteristics of photosynthesis, carbon–nitrogen metabolism, and plant hormone signal transduction to enhance drought resistance in industrial hemp.

Sugarcane (Saccharum spp. hybrid) is frequently affected by seasonal drought, which causes substantial declines in quality and yield. To understand the drought resistance mechanisms of S. officinarum, the main species of modern sugarcane, at a molecular level, we carried out a comparative analysis of transcriptome and metabolome profiling of the sugarcane variety Badila under drought stress (DS). Compared with control group (CG) plants, plants exposed to DS had 13,744 (6663 up-regulated and 7081 down-regulated) differentially expressed genes (DEGs). GO and KEGG analysis showed that the DEGs were enriched in photosynthesis-related pathways and most DEGs had down-regulated expression. Moreover, the chlorophyll content, photosynthesis (Photo), stomatal conductance (Cond), intercellular carbon dioxide concentration (Ci) and transpiration rate (Trmmol) were sharply decreased under DS. These results indicate that DS has a significant negative influence on photosynthesis in sugarcane. Metabolome analysis identified 166 (37 down-regulated and 129 up-regulated) significantly regulated metabolites (SRMs). Over 50% of SRMs were alkaloids, amino acids and their derivatives, and lipids. The five most significantly enriched KEGG pathways among SRMs were Aminoacyl-tRNA biosynthesis, 2-Oxocarboxylic acid metabolism, Biosynthesis of amino acids, Phenylalanine metabolism, and Arginine and proline metabolism (p < 0.05). Comparing CG with DS for transcriptome and metabolome profiling (T_CG/DS and M_CG/DS, respectively), we found three of the same KEGG-enriched pathways, namely Biosynthesis of amino acids, Phenylalanine metabolism and Arginine and proline metabolism. The potential importance of Phenylalanine metabolism and Arginine and proline metabolism was further analyzed for response to DS in sugarcane. Seven SRMs (five up-regulated and two down-regulated) and 60 DEGs (17 up-regulated and 43 down-regulated) were enriched in Phenylalanine metabolism under DS, of which novel.31261, Sspon.04G0008060-1A, Sspon.04G0008060-2B and Sspon.04G0008060-3C were significantly correlated with 7 SRMs. In Arginine and proline metabolism, eight SRMs (seven up-regulated and one down-regulated) and 63 DEGs (32 up-regulated and 31 down-regulated) were enriched, of which Sspon.01G0026110-1A (OAT) and Sspon.03G0002750-3D (P5CS) were strongly associated with proline (r > 0.99). These findings present the dynamic changes and possible molecular mechanisms of Phenylalanine metabolism as well as Arginine and proline metabolism under DS and provide a foundation for future research and sugarcane improvement.

Salt stress is a major factor limiting the growth and yield of soybean (Glycine max). Wild soybeans (Glycine soja) contain high allelic diversity and beneficial alleles that can be re-introduced into domesticated soybeans to improve adaption to the environment. However, very few beneficial alleles have been identified from wild soybean. Here, we demonstrate that wild soybean is more salt tolerant than cultivated soybean and examine dehydration responsive element-binding (DREB) family transcription factor genes to look for advantageous alleles that might improve drought tolerance in cultivated soybean. Our genome-wide analysis identified 103 DREB genes from the Glycine max genome. By combined RNA-sequencing and population genetics of wild, landrace, and cultivated soybean accessions, we show that the natural variation in DREB3a and DREB3b is related to differences in salt tolerance in soybean accessions. Interestingly, DREB3b, but not DREB3a, appears to have undergone artificial selection. Soybean plants carrying the wild soybean DREB3b allele (DREB3b39Del) are more salt tolerant than those containing the reference genome allele (DREB3bRef). Together, our results suggest that the loss of the DREB3b39Del allele through domestication of cultivated soybean may be associated with a reduction in salt tolerance. Our findings provide crucial information for improving salt tolerance in soybean through molecular breeding.

Studying the mechanism of drought stress in soybean root at vegetative cotyledon (VC) stage by soaking seeds with uniconazole revealed new insights into soybean stress physiology. Therefore, a completely random pot experiments with different time gradients for water cut-off (24, 48, 72, 96 and 120 h, respectively) were carried out with uniconazole (0.4 mgL−1) with respect to morphological, microscopic, ultramicroscopic, physiological, and molecular studies on varieties Hefeng55 (H50, drought tolerant variety) and Kenfeng16 (K16, drought susceptible variety). Results revealed that uniconazole effectively alleviated the inhibition on root growth caused by drought stress, increased the number of root tips, significantly reduced lignification of vessels, alleviated the damage of mitochondria and nucleus caused by drought stress, further strengthened osmotic adjustment system and antioxidant system, especially when the soil moisture content was less than 14%, broke expression restriction of IAA due to drought stress, and inhibited GA3 generation; finally, we found that high-intensity drought stress significantly increased the expression levels of GmNAC003, GmNAC004, GmNAC015, GmNAC020, GmHK07, GmRR01, GmRR02 and GmRR16 genes relating to drought tolerance, while uniconazole had a significant inhibitory effect on GmNAC003, GmNAC004, GmNAC015, GmNAC020, GmRR01, GmRR02 and GmRR16 genes. Our results provided a reference for the mechanism of drought resistance in legume and the effect of uniconazole on alleviating drought stress.

Soil salinization seriously restricts the growth and yield of soybeans. However, little information is available on the early growth stages of soybeans which are subjected to the gibberellin biosynthesis inhibitor, prohexadione-calcium (Pro-Ca). This study aimed to investigate the effects of exogenous Pro-Ca on saline-alkali stress-induced damages to photosynthesis and antioxidant defenses in soybean (Glycine max L.) seedlings. At the V3 growth stage, salt-tolerant genotype Hefeng 50 (HF50) and salt-sensitive genotype Kenfeng 16 (KF16) were subjected to 110 mmol L−1 mixed saline-alkali stress respectively, and then 100 mg L−1 Pro-Ca was sprayed on the leaves. Our results showed that saline-alkali stress accelerated the degradation of thylakoids, inhibited chlorophyll synthesis, reduced shoot dry weight, electron transfer rate (ETR), and peroxidase (POD) activity, the concentration of ascorbic acid (AsA) and soluble sugar, but enhanced the concentration of proline, hydrogen peroxide (H2O2) and the rate of superoxide radical (O2∙−) generation. Additionally, saline-alkali stress induced a lower decrease of the net photosynthetic rate (Pn), potential activity of PSII (Fv/F0), and maximum quantum yield of PSII (Fv/Fm) in salt-tolerant HF50 than in salt-sensitive KF16. Nevertheless, foliar spraying of exogenous Pro-Ca increased the chlorophyll content, Pn, Fv/F0, and Fv/Fm. These results were more prominent when Pro-Ca was applied to KF16 under saline-alkali conditions. Furthermore, exogenous application of Pro-Ca retarded the degradation of thylakoids, increased the ETR and the accumulation of AsA, soluble sugar, and proline, activated the activities of superoxide dismutase (SOD), catalase (CAT), and POD, and decreased the concentration of malondialdehyde (MDA), electrolyte leakage (EL), O2∙−, and H2O2. These results indicated that Pro-Ca could effectively protect soybean seedlings against damage from saline-alkali stress by regulating seedling phenotype, photosynthetic apparatus, antioxidant defense, and osmoregulation.

Sugarcane (Saccharum spp. hybrid) is an important crop for sugar and biofuels, and often suffers from water shortages during growth. Currently, there is limited knowledge concerning the molecular mechanism involved in sugarcane response to drought stress (DS) and whether chitooligosaccharide could alleviate DS. Here, we carried out a combined transcriptome and metabolome of sugarcane in three different treatment groups: control group (CG), DS group, and DS + chitooligosaccharide group (COS). A total of 12,275 (6404 up-regulated and 5871 down-regulated) differentially expressed genes (DEGs) were identified when comparing the CG and DS transcriptomes (T_CG/DS), and 2525 (1261 up-regulated and 1264 down-regulated) DEGs were identified in comparing the DS and COS transcriptomes (T_DS/COS). GO and KEGG analysis showed that DEGs associated with photosynthesis were significantly enriched and had down-regulated expression. For T_DS/COS, photosynthesis DEGs were also significantly enriched but had up-regulated expression. Together, these results indicate that DS of sugarcane has a significantly negative influence on photosynthesis, and that COS can alleviate these negative effects. In metabolome analysis, lipids, others, amino acids and derivatives and alkaloids were the main significantly different metabolites (SDMs) observed in sugarcane response to DS, and COS treatment reduced the content of these metabolites. KEGG analysis of the metabolome showed that 2-oxocarboxylic acid metabolism, ABC transporters, biosynthesis of amino acids, glucosinolate biosynthesis and valine, leucine and isoleucine biosynthesis were the top-5 KEGG enriched pathways when comparing the CG and DS metabolome (M_CG/DS). Comparing DS with COS (M_DS/COS) showed that purine metabolism and phenylalanine metabolism were enriched. Combined transcriptome and metabolome analysis revealed that pyruvate and phenylalanine metabolism were KEGG-enriched pathways for CG/DS and DS/COS, respectively. For pyruvate metabolism, 87 DEGs (47 up-regulated and 40 down-regulated) and five SDMs (1 up-regulated and 4 down-regulated) were enriched. Pyruvate was closely related with 14 DEGs (|r| > 0.99) after Pearson’s correlation analysis, and only 1 DEG (Sspon.02G0043670-1B) was positively correlated. For phenylalanine metabolism, 13 DEGs (7 up-regulated and 6 down-regulated) and 6 SDMs (1 up-regulated and 5 down-regulated) were identified. Five PAL genes were closely related with 6 SDMs through Pearson’s correlation analysis, and the novel.31257 gene had significantly up-regulated expression. Collectively, our results showed that DS has significant adverse effects on the physiology, transcriptome, and metabolome of sugarcane, particularly genes involved in photosynthesis. We further show that COS treatment can alleviate these negative effects.

Abstract Background Continuous cropping stress involves such factors as biological barriers, allelopathic autotoxicity, deterioration of soil physicochemical properties, and soil fertility imbalance and is regarded as a kind of comprehensive stress limiting soybean yield and quality. Genomic DNA methylation is an important regulatory mechanism for plants to resist various environmental stresses. Therefore, it is especially worthwhile to reveal genomic methylation characteristics under stress and clarify the relationship between DNA methylation status and continuous cropping stress adaptability in soybean. Results We generated a genome-wide map of cytosine methylation induced by this kind of comprehensive stress in a tolerant soybean variety (Kang Xian 2, KX2) and a sensitive variety (He Feng, HF55) using whole-genome bisulfite sequencing (WGBS) technology. The expression of DNA demethylase genes was detected using real-time quantitative PCR (qRT-PCR). The functions of differentially methylated genes (DMGs) involved in stress response in biochemical metabolism and genetic information transmission were further assessed based on Gene Ontology (GO) annotation and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis. The results showed that genomic DNA demethylation was closely related to continuous cropping comprehensive stress adaptability in soybean, which was further verified by the increasing expression of DNA demethylases ROS1 and DML. The demethylation of mCpG and mCpHpG (mCpApG preferred) contexts was more critical, which mainly occurred in gene-regulatory regions at the whole-chromosome scale. Moreover, this kind of stress adaptability may be related to various stress responders generated through strengthened glucose catabolism and amino acid and fatty acid anabolism, as well as fidelity transmission of genetic information. Conclusions Genomic DNA demethylation was closely associated with continuous cropping comprehensive stress adaptability, highlighting the promising potential of screening continuous cropping-tolerant cultivars by DNA methylation index and further exploring the application of DNA demethylases in soybean breeding.

For the purpose of functional validation, the mung bean (Vigna radiata) VrPR gene was cloned and overexpressed in Arabidopsis thaliana. The findings revealed that the ORF of VrPR contained 1200 bp, in which 399 amino acids were encoded. Bioinformatics analysis showed that the VrPR protein belonged to the NADB Rossmann superfamily, which was one of the non-transmembrane hydrophilic proteins. VrPR was assumed to have 44 amino acid phosphorylation sites and be contained in chloroplasts. The VrPR secondary structure comprised of random coil, α helix, β angle, and extended chain, all of which were quite compatible with the anticipated tertiary structure. Moreover, analysis of the phylogenetic tree indicated that the soybean PR (Glyma.12G222200) and VrPR were closely related. Furthermore, chlorophyll content in leaves is markedly increased in Arabidopsis when VrPR is overexpressed. Our findings will serve as a reference for more functional studies on the PR genes in mung bean. [ABSTRACT FROM AUTHOR]