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Root-knot nematodes (RKNs) are plant pests that infect the roots of host plants. Bacillus thuringiensis (Bt) nematicidal proteins exhibited toxicity to nematodes. However, the application of nematicidal proteins for plant protection is hampered by the lack of effective delivery systems in transgenic plants. In this study, we discovered the accumulation of leucoplasts (root plastids) in galls and RKN-induced giant cells. RKN infection causes the degradation of leucoplasts into small vesicle-like structures, which are responsible for delivering proteins to RKNs, as observed through confocal microscopy and immunoelectron microscopy. We showed that different-sized proteins from leucoplasts could be taken up by Meloidogyne incognita female. To further explore the potential applications of leucoplasts, we introduced the Bt crystal protein Cry5Ba2 into tobacco and tomato leucoplasts by fusing it with a transit peptide. The transgenic plants showed significant resistance to RKNs. Intriguingly, RKN females preferentially took up Cry5Ba2 protein when delivered through plastids rather than the cytosol. The decrease in progeny was positively correlated with the delivery efficiency of the nematicidal protein. In conclusion, this study offers new insights into the feeding behavior of RKNs and their ability to ingest leucoplast proteins, and demonstrates that root leucoplasts can be used for delivering nematicidal proteins, thereby offering a promising approach for nematode control., (Copyright © 2024 The Author. Published by Elsevier Inc. All rights reserved.)

Phosphate deficiency and drought are significant environmental constraints that impact both the productivity and quality of wheat. The interaction between phosphorus and water facilitates their mutual absorption processes in plants. Under conditions of both phosphorus deficiency and drought stress, we observed a significant upregulation in the expression of wheat MYB-CC transcription factors through the transcriptome analysis. 52 TaMYB-CC genes in wheat were identified and analyzed their evolutionary relationships, structures, and expression patterns. The TaMYB-CC5 gene exhibited specific expression in roots and demonstrated significant upregulation under phosphorus deficiency and drought stress compared to other TaMYB-CC genes. The overexpression of TaMYB-CC5A in Arabidopsis resulted in a significant increase of root length under stress conditions, thereby enhancing tolerance to phosphate starvation and drought stress. The wheat lines with silenced TaMYB-CC5 genes exhibited reduced root length under stress conditions and increased sensitivity to phosphate deficiency and drought stress. In addition, silencing the TaMYB-CC5 genes resulted in altered phosphorus content in leaves but did not lead to a reduction in phosphorus content in roots. Enrichment analysis the co-expression genes of TaMYB-CC5 transcription factors, we found the zinc-induced facilitator-like (ZIFL) genes were prominent associated with TaMYB-CC5 gene. The TaZIFL1, TaZIFL2, and TaZIFL5 genes were verified specifically expressed in roots and regulated by TaMYB-CC5 transcript factor. Our study reveals the pivotal role of the TaMYB-CC5 gene in regulating TaZIFL genes, which is crucial for maintaining normal root growth under phosphorus deficiency and drought stress, thereby enhanced resistance to these abiotic stresses in wheat., Competing Interests: Declaration of competing interest The authors declare no conflicts of interest., (Copyright © 2024 Elsevier Masson SAS. All rights reserved.)

Barley (Hordeum vulgare) is an important global cereal crop and a model in genetic studies. Despite advances in characterising barley genomic resources, few mutant studies have identified genes controlling root architecture and anatomy, which plays a critical role in capturing soil resources. Our phenotypic screening of a TILLING mutant collection identified line TM5992 exhibiting a short-root phenotype compared with wild-type (WT) Morex background. Outcrossing TM5992 with barley variety Proctor and subsequent SNP array-based bulk segregant analysis, fine mapped the mutation to a cM scale. Exome sequencing pinpointed a mutation in the candidate gene HvPIN1a, further confirming this by analysing independent mutant alleles. Detailed analysis of root growth and anatomy in Hvpin1a mutant alleles exhibited a slower growth rate, shorter apical meristem and striking vascular patterning defects compared to WT. Expression and mutant analyses of PIN1 members in the closely related cereal brachypodium (Brachypodium distachyon) revealed that BdPIN1a and BdPIN1b were redundantly expressed in root vascular tissues but only Bdpin1a mutant allele displayed root vascular defects similar to Hvpin1a. We conclude that barley PIN1 genes have sub-functionalised in cereals, compared to Arabidopsis (Arabidopsis thaliana), where PIN1a sequences control root vascular patterning., (© 2024 The Author(s). New Phytologist © 2024 New Phytologist Foundation.)

Plants grow by anchoring their roots in the soil, acquiring essential water and nutrients for growth, and interacting with other signaling factors in the soil. Root systems are crucial for both the basic growth and development of plants and their response to external environmental stimuli. Under different environmental conditions, the configuration of root systems in plants can undergo significant changes, with their strength determining the plant's ability to adapt to the environment. Therefore, understanding the mechanisms by which environmental factors regulate root development is essential for crop root architecture improvement and breeding for stress resistance. This paper summarizes the research progress in genetic regulation of root development of the model plant Arabidopsis thaliana (L.) Heynh. amidst diverse environmental stimuli over the past five years. Specifically, it focuses on the regulatory networks of environmental signals, encompassing light, energy, temperature, water, nutrients, and reactive oxygen species, on root development. Furthermore, it provides prospects for the application of root architecture improvement in crop breeding for stress resistance and nutrient efficiency., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Masson SAS. All rights reserved.)

Mediator, a multiprotein complex, is an important component of the transcription machinery. In plants, the latest studies have established that it functions as a signal processor that conveys transcriptional signals from transcription factors to RNA polymerase II. Mediator has been found to be involved in different developmental and stress-adaptation conditions, ranging from embryo, root, and shoot development to flowering and senescence, and also in responses to different biotic and abiotic stresses. In the last decade, significant progress has been made in understanding the role of Mediator subunits in root development. They have been shown to transcriptionally regulate development of almost all the components of the root system architecture-primary root, lateral roots, and root hairs. They also have a role in nutrient acquisition by the root. In this review, we discuss all the known functions of Mediator subunits during root development. We also highlight the role of Mediator as a nodal point for processing different hormone signals that regulate root morphogenesis and growth., (© The Author(s) 2024. Published by Oxford University Press on behalf of the Society for Experimental Biology. All rights reserved. For commercial re-use, please contact reprints@oup.com for reprints and translation rights for reprints. All other permissions can be obtained through our RightsLink service via the Permissions link on the article page on our site—for further information please contact journals.permissions@oup.com.)

Rhizobial attachment to host legume roots is the first physical interaction of bacteria and plants in symbiotic nitrogen fixation. The pH-dependent primary attachment of Rhizobium leguminosarum biovar viciae 3841 to Pisum sativum (pea) roots was investigated by genome-wide insertion sequencing, luminescence-based attachment assays, and proteomic analysis. Under acid, neutral, or alkaline pH, a total of 115 genes are needed for primary attachment under one or more environmental pH, with 22 genes required for all. These include components of cell surfaces and membranes, together with enzymes that construct and modify them. Mechanisms of dealing with stress also play a part; however, exact requirements vary depending on environmental pH. RNASeq showed that knocking out the two transcriptional regulators required for attachment causes massive changes in the bacterial cell surface. Approximately half of the 54 proteins required for attachment at pH 7.0 have a role in the later stages of nodule formation. We found no evidence for a single rhicadhesin responsible for alkaline attachment, although sonicated cell surface fractions inhibited root attachment at alkaline pH. Our results demonstrate the complexity of primary root attachment and illustrate the diversity of mechanisms involved., Importance: The first step by which bacteria interact with plant roots is by attachment. In this study, we use a combination of insertion sequencing and biochemical analysis to determine how bacteria attach to pea roots and how this is influenced by pH. We identify several key adhesins, which are molecules that enable bacteria to stick to roots. This includes a novel filamentous hemagglutinin which is needed at all pHs for attachment. Overall, 115 proteins are required for attachment at one or more pHs., Competing Interests: The authors declare no conflict of interest.

Background: Brassica napus L. (B. napus) is susceptible to waterlogging stress during different cultivation periods. Therefore, it is crucial to enhance the resistance to waterlogging stress to achieve a high and stable yield of B. napus., Results: Here we observed significant differences in the responses of two B. napus varieties in root under waterlogging stress. The sensitive variety (23651) exhibited a more pronounced and rapid reduction in cell wall thickness and root integrity compared with the tolerant variety (Santana) under waterlogging stress. By module clustering analysis based on transcriptome data, we identified that cell wall polysaccharide metabolism responded to waterlogging stress in root. It was found that pectin content was significantly reduced in the sensitive variety compared with the tolerant variety. Furthermore, transcriptome analysis revealed that the expression of two homologous genes encoding polygalacturonase-inhibiting protein 2 (PGIP2), involved in polysaccharide metabolic pathways, was highly upregulated in root of the tolerant variety under waterlogging stress. BnaPGIP2s probably confer waterlogging resistance by inhibiting the activity of polygalacturonases (PGs), which in turn reduces the degradation of the pectin backbone polygalacturonic acid., Conclusions: Our findings demonstrate that cell wall polysaccharides in root plays a vital role in response to the waterlogging stress and provide a theoretical foundation for breeding waterlogging resistance in B. napus varieties., (© 2024. The Author(s).)

The Cichorium plants are particularly notable due to their remarkable therapeutic and medicinal properties, besides being used as food and conventional medication. Although Cichorium plants have been studied for their phytoconstituents and biological activities, there is limited knowledge about the constituents of the roots of C. bottae. A phytochemical study of the 90% MeOH extract of C. bottae roots resulted in the isolation of twelve compounds belonging to guaianolide sesquiterpene lactones, sesquiterpene lactone glucosides, and phenolic derivatives, of which two compounds designated as 9α-hydroxycrepediaside B (1) and cichobotinal (2) were previously undescribed. The isolated compounds were assessed for their anti-inflammatory potential through the inhibition of inducible nitric oxide synthase (iNOS) and resultant decrease in nitric oxide generation in LPS-induced macrophages. Among the isolates, compounds 2 and 11 (8-deoxylactucin) inhibited iNOS activity with IC 50 values of 21.0 ± 4 and 6.8 ± 0.1 μM, respectively. The methanolic extract of C. bottae inhibited iNOS with an IC 50 of 10.5 ± 0.5 μg/mL., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

Understanding the mechanisms that regulate plant root growth under soil drying is an important challenge in root biology. We observed that moderate soil drying promotes wheat root growth. To understand whether metabolic and hormonic changes are involved in this regulation, we performed transcriptome sequencing on wheat roots under well-watered and moderate soil drying conditions. The genes upregulated in wheat roots under soil drying were mainly involved in starch and sucrose metabolism and benzoxazinoid biosynthesis. Various plant hormone-related genes were differentially expressed during soil drying. Quantification of the plant hormones under these conditions showed that the concentrations of abscisic acid (ABA), cis-zeatin (CZ), and indole-3-acetic acid (IAA) significantly increased during soil drying, whereas the concentrations of salicylic (SA), jasmonic (JA), and glycosylated salicylic (SAG) acids significantly decreased. Correlation analysis of total root length and phytohormones indicated that CZ, ABA, and IAA are positively associated with wheat root length. These results suggest that changes in metabolic pathways and plant hormones caused by moderate soil drying help wheat roots grow into deeper soil layers.

Nitrogen (N) is essential for sugar beet ( Beta vulgaris L.), a highly N-demanding sugar crop. This study investigated the morphological, subcellular, and microRNA-regulated responses of sugar beet roots to low N (LN) stress (0.5 mmol/L N) to better understand the N perception, uptake, and utilization in this species. The results showed that LN led to decreased dry weight of roots, N accumulation, and N dry matter production efficiency, along with damage to cell walls and membranes and a reduction in organelle numbers (particularly mitochondria). Meanwhile, there was an increase in root length (7.2%) and branch numbers (29.2%) and a decrease in root surface area (6.14%) and root volume (6.23%) in sugar beet after 7 d of LN exposure compared to the control (5 mmol/L N). Transcriptomics analysis was confirmed by qRT-PCR for 6 randomly selected microRNAs, and we identified 22 differentially expressed microRNAs (DEMs) in beet root under LN treatment. They were primarily enriched in functions related to binding (1125), ion binding (641), intracellular (437) and intracellular parts (428), and organelles (350) and associated with starch and sucrose metabolism, tyrosine metabolism, pyrimidine metabolism, amino sugar and nucleotide sugar metabolism, and isoquinoline alkaloid biosynthesis, as indicated by the GO and KEGG analyses. Among them, the upregulated miR156a, with conserved sequences, was identified as a key DEM that potentially targets and regulates squamosa promoter-binding-like proteins (SPLs, 104889216 and 104897537) through the microRNA-mRNA network. Overexpression of miR156a (MIR) promoted root growth in transgenic Arabidopsis, increasing the length, surface area, and volume. In contrast, silencing miR156a (STTM) had the opposite effect. Notably, the fresh root weight decreased by 45.6% in STTM lines, while it increased by 27.4% in MIR lines, compared to the wild type (WT). It can be inferred that microRNAs, especially miR156, play crucial roles in sugar beet root's development and acclimation to LN conditions. They likely facilitate active responses to N deficiency through network regulation, enabling beet roots to take up nutrients from the environment and sustain their vital life processes.

The bottle gourd [ Lagenaria siceraria (Molina) Standl.] is often utilized as a rootstock for watermelon grafting. This practice effectively mitigates the challenges associated with continuous cropping obstacles in watermelon cultivation. The lower ground temperature has a direct impact on the rootstocks' root development and nutrient absorption, ultimately leading to slower growth and even the onset of yellowing. However, the mechanisms underlying the bottle gourd's regulation of root growth in response to low root zone temperature (LRT) remain elusive. Understanding the dynamic response of bottle gourd roots to LRT stress is crucial for advancing research regarding its tolerance to low temperatures. In this study, we compared the physiological traits of bottle gourd roots under control and LRT treatments; root sample transcriptomic profiles were monitored after 0 h, 48 h and 72 h of LRT treatment. LRT stress increased the malondialdehyde (MDA) content, relative electrolyte permeability and reactive oxygen species (ROS) levels, especially H 2 O 2 and O 2- . Concurrently, LRT treatment enhanced the activities of antioxidant enzymes like superoxide dismutase (SOD) and peroxidase (POD). RNA-Seq analysis revealed the presence of 2507 and 1326 differentially expressed genes (DEGs) after 48 h and 72 h of LRT treatment, respectively. Notably, 174 and 271 transcription factors (TFs) were identified as DEGs compared to the 0 h control. We utilized quantitative real-time polymerase chain reaction (qRT-PCR) to confirm the expression patterns of DEGs belonging to the WRKY, NAC, bHLH, AP2/ERF and MYB families. Collectively, our study provides a robust foundation for the functional characterization of LRT-responsive TFs in bottle gourd roots. Furthermore, these insights may contribute to the enhancement in cold tolerance in bottle gourd-type rootstocks, thereby advancing molecular breeding efforts.

Over evolutionary time, plants have developed sophisticated regulatory mechanisms to adapt to fluctuating nitrogen (N) environments, ensuring that their growth is balanced with their responses to N stress. This study explored the potential of L-tryptophan (Trp) in regulating sorghum root growth under conditions of N limitation. Here, two distinct sorghum genotypes (low-N tolerance 398B and low-N sensitive CS3541) were utilized for investigating effect of low-N stress on root morphology and conducting a comparative transcriptomics analysis. Our foundings indicated that 398B exhibited longer roots, greater root dry weights, and a higher Trp content compared to CS3541 under low-N conditions. Furthermore, transcriptome analysis revealed substantial differences in gene expression profiles related to Trp pathway and carbon (C) and N metabolism pathways between the two genotypes. Additional experiments were conducted to assess the effects of exogenous Trp treatment on the interplay between sorghum root growth and low-N tolerance. Our observations showed that Trp-treated plants developed longer root and had elevated levels of Trp and IAA under low-N conditons. Concurrently, these plants demonstrated stronger physiological activities in C and N metabolism when subjected to low-N stress. These results underscored the pivotal role of Trp on root growth and low-N stress responses by balancing IAA levels and C and N metabolism. This study not only deepens our understanding of how plants maintain growth plasticity during environmental stress but also provides valuable insights into the availability of amino acid in crops, which could be instrumental in developing strategies for promoting crop resilience to N deficiency., Competing Interests: Declaration of competing interest The authors declare no conflict of interests., (Copyright © 2024 Elsevier Masson SAS. All rights reserved.)

Euphorbia himalayensis Boiss. is an alpine member of the Euphorbiaceae family. Its dried roots have been used to treat digestive problems and chest congestion in traditional Tibetan and Mongolian medicine. Despite thousands of years of use in medicine, the bioactive compounds of the root remain unknown. Herein, we isolated a novel aqueous-soluble polysaccharide (EHP2) from the E. himalayensis root and determined its structural characteristics via high-performance gel permeation chromatography, Fourier-transform infrared spectroscopy, gas chromatography-mass spectrometry, and nuclear magnetic resonance spectrometry. The homogeneous molecular weight of EHP2 was 23.6 kDa with narrow polydisperity (Mw/Mn = 1.4), and EHP2 mainly comprised of glucose (86.4%), galactose (11.9%) and mannose (1.7%). The major backbone of EHP2 was →4)-α-D-GalAp-(1 → 4)-α-D-Glcp-(1 → and the branch chain was α-D-Glcp-(1→. The antioxidant activity of the EHP2 was evaluated by 1,1-diphenyl-2-picrylhydrazyl (DPPH) and superoxide anion radical scavenging assays, and antioxidant enzyme activity (SOD, GSH and MDA) was determined in human umbilical vein endothelial cells (HUVECs). The EHP2 demonstrated lower potential scavenging effects on DPPH and superoxide free radical scavenger than ascorbic acid, and in HUVECs, it led to increased SOD and GSH activities and decreased MDA levels. This study is the first to describe an E. himalayensis polysaccharide compound with potential antioxidant activity., Competing Interests: Declaration of competing interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: Sarangowa Ochir reports financial support was provided by Inner Mongolia Medical University. Lechaolu Bao reports financial support was provided by Inner Mongolia Autonomous Region Natural Science Foundation. Sarangowa Ochir reports statistical analysis was provided by Yangzhou BoRui Saccharide Biotech Co. Ltd. If there are other authors, they declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Authors. Published by Elsevier B.V. All rights reserved.)

Background: Soybean establishes a mutualistic interaction with nitrogen-fixing rhizobacteria, acquiring most of its nitrogen requirements through symbiotic nitrogen fixation. This crop is susceptible to water deficit; evidence suggests that its nodulation status-whether it is nodulated or not-can influence how it responds to water deficit. The translational control step of gene expression has proven relevant in plants subjected to water deficit., Results: Here, we analyzed soybean roots' differential responses to water deficit at transcriptional, translational, and mixed (transcriptional + translational) levels. Thus, the transcriptome and translatome of four combined-treated soybean roots were analyzed. We found hormone metabolism-related genes among the differentially expressed genes (DEGs) at the translatome level in nodulated and water-restricted plants. Also, weighted gene co-expression network analysis followed by differential expression analysis identified gene modules associated with nodulation and water deficit conditions. Protein-protein interaction network analysis was performed for subsets of mixed DEGs of the modules associated with the plant responses to nodulation, water deficit, or their combination., Conclusions: Our research reveals that the stand-out processes and pathways in the before-mentioned plant responses partially differ; terms related to glutathione metabolism and hormone signal transduction (2 C protein phosphatases) were associated with the response to water deficit, terms related to transmembrane transport, response to abscisic acid, pigment metabolic process were associated with the response to nodulation plus water deficit. Still, two processes were common: galactose metabolism and branched-chain amino acid catabolism. A comprehensive analysis of these processes could lead to identifying new sources of tolerance to drought in soybean., (© 2024. The Author(s).)

Two novel strains, designated APW6 T and APW11 T , were isolated from artificial pond water, and one novel strain, designated PFR6 T , was isolated from a Viola mandshurica root. These strains were found to be Gram-negative, rod-shaped, motile by means of flagella, and oxidase-positive. Growth conditions of the type strains were as follows: APW6 T , 15-43 °C (optimum, 28 °C), pH 6.0-12.0 (optimum, pH 7.0), with no salinity; APW11 T , 4-35 °C (optimum, 25 °C), pH 6.0-11.0 (optimum, pH 9.0), with 0-1 % NaCl (w/v, optimum 0 %); PFR6 T , 10-38 °C (optimum 28 °C), pH 6.0-12.0 (optimum, pH 7.0), with 0-2 % NaCl (w/v; optimum, 0 %). Strains APW6 T , APW11 T , and PFR6 T belonged to the genus Roseateles , having the most 16S rRNA gene sequence similarity to Roseateles saccharophilus DSM 654 T (98.1 %), Roseateles oligotrophus CHU3 T (98.7 %), and Roseateles puraquae CCUG 52769 T (98.1 %). The estimated genome sizes of APW6 T , APW11 T , and PFR6 T were 50 50 473, 56 70 008, and 52 16 869 bp, respectively and the G+C contents were 69.5, 66, and 68.5 mol%. The digital DNA-DNA hybridization, average amino acid identity, and average nucleotide identity values among the novel strains and related taxa were all lower than 22.4, 74.7, and 78.9 %, respectively. The predominant cellular fatty acids (>10 %) of all strains were summed feature 3 (comprising C 16 : 1  ω 6 c and/or C 16 : 1  ω 7 c ) and C 16 : 0 . PFR6 T also had summed feature 8 (comprising C 18 :  1   ω 7 c and/or C 18 :  1   ω 6 c ) as a major fatty acid. The polar lipid profile of all strains contained phosphatidylethanolamine, phosphoaminoglycolipid, and phosphoglycolipid. The distinct phylogenetic, physiological, and chemotaxonomic features reported in this study indicate that strains APW6 T , APW11 T , and PFR6 T represent novel species within the genus Roseateles , for which the names Roseateles subflavus sp. nov., with the type strain APW6 T (=KACC 22877 T =TBRC 16606 T ), Roseateles aquae sp. nov., with the type strain APW11 T (=KACC 22878 T =TBRC 16607 T ), and Roseateles violae sp. nov (=KACC 23257 T =TBRC 17653 T ) are respectively proposed.

Plants partly optimize their water recruitment from the growth medium by directing root growth toward a moisture source, a phenomenon termed hydrotropism. The default mechanism of downward growth, termed gravitropism, often functions to counteract hydrotropism when the water-potential gradient deviates from the gravity vector. This review addresses the identity of the root sites in which hydrotropism-regulating factors function to attenuate gravitropism and the interplay between these various factors. In this context, the function of hormones, including auxin, abscisic acid, and cytokinins, as well as secondary messengers, calcium ions, and reactive oxygen species in the conflict between these two opposing tropisms is discussed. We have assembled the available data on the effects of various chemicals and genetic backgrounds on both gravitropism and hydrotropism, to provide an up-to-date perspective on the interactions that dictate the orientation of root tip growth. We specify the relevant open questions for future research. Broadening our understanding of root mechanisms of water recruitment holds great potential for providing advanced approaches and technologies that can improve crop plant performance under less-than-optimal conditions, in light of predicted frequent and prolonged drought periods due to global climate change., (© 2024 The Authors. The Plant Journal published by Society for Experimental Biology and John Wiley & Sons Ltd.)

Background and Aims: Internal root aeration is essential for root growth in waterlogged conditions. Aerenchyma provides a path for oxygen to diffuse to the roots. In most wetland species, including rice, a barrier to radial oxygen loss (ROL) allows more of the oxygen to diffuse to the root tip, enabling root growth into anoxic soil. Most dryland crops, including barley, do not form a root ROL barrier. We previously found that abscisic acid (ABA) signalling is involved in the induction of ROL barrier formation in rice during waterlogging. Although rice typically does not form a tight ROL barrier in roots in aerated conditions, an ROL barrier with suberized exodermis was induced by application of exogenous ABA. Therefore, we hypothesized that ABA application could also trigger root ROL barrier formation with hypodermal suberization in barley., Methods: Formation of an ROL barrier was examined in roots in different exogenous ABA concentrations and at different time points using cylindrical electrodes and Methylene Blue staining. Additionally, we evaluated root porosity and observed suberin and lignin modification. Suberin, lignin and Casparian strips in the cell walls were observed by histochemical staining. We also evaluated the permeability of the apoplast to a tracer., Key Results: Application of ABA induced suberization and ROL barrier formation in the adventitious roots of barley. The hypodermis also formed lignin-containing Casparian strips and a barrier to the infiltration of an apoplastic tracer (periodic acid). However, ABA application did not affect root porosity., Conclusions: Our results show that in artificial conditions, barley can induce the formation of ROL and apoplastic barriers in the outer part of roots if ABA is applied exogenously. The difference in ROL barrier inducibility between barley (an upland species) and rice (a wetland species) might be attributable to differences in ABA signalling in roots in response to waterlogging conditions., (© The Author(s) 2024. Published by Oxford University Press on behalf of the Annals of Botany Company. All rights reserved. For commercial re-use, please contact reprints@oup.com for reprints and translation rights for reprints. All other permissions can be obtained through our RightsLink service via the Permissions link on the article page on our site—for further information please contact journals.permissions@oup.com.)

Bistorta vivipara is a medicinal plant with a long history, but there are few studies on the effects of its medicinal components and endophytic bacteria on the accumulation of secondary metabolites. Therefore, in this study, non-targeted metabolomics techniques and 16s rDNA techniques were used to study B. vivipara from different regions. A total of 1290 metabolites and 437 differential metabolites were identified from all samples. Among them, flavonoids, isoflavonoids, and benzopyrans are the main medicinal components of B. vivipara ; these have potential anticancer, antiviral, and antioxidant properties, as well as potential applications for the treatment of atrial fibrillation. In addition, irigenin, an important medicinal component, was identified for the first time. The endophytic bacterial communities in the root tissues of B. vivipara from different regions were also different in composition and richness. Hierarchical clustering heat map analysis showed that Proteobacteria and Actinobacteriota bacteria significantly affected the accumulation of many medicinal components in the roots of B. vivipara .

To better understand the dynamics and functional roles of root pressure, we represent a novel and the first complete analytical model for root pressure, which can be applied to complex roots/shoots. The osmotic volume of a single root is equal to that of the vessel lumen in fine roots and adjacent apoplastic spaces. Water uptake occurs via passive osmosis and active solute uptake ( J s * , osmol s -1 ), resulting in the osmolyte concentration C r (mol·kg -1 of water) at a fixed osmotic volume. Solute loss occurs via two passive processes: radial diffusion of solute K m (C r - C soil ) from fine roots to soil, where K m is the diffusional constant and C soil is the soil-solute concentration, and the mass flow of solute and water into the plant from the fine roots. The proposed model predicts the quadratic function of root pressure (P r ), P r 2 + b P r + c = 0 , where b and c are the functions of plant hydraulic resistance, soil water potential, solute flux and gravitational potential. The model demonstrates the root pressure-mediated distribution of water through the hydraulic architecture of a 6.8-m-tall bamboo shoot. This model provides a theoretical basis to test the functional roles of root pressure in shaping the hydraulic architecture and refilling potential xylem embolisms., (© 2023 John Wiley & Sons Ltd.)

Main Conclusion: We describe a user-optimized sample holder EasyClick for medium-sized plants that reduces root side movements and thus greatly extends the duration of live cell confocal microscopy. Preparation and mounting of the samples are key factors for successful live cell microscopy. To acquire biologically relevant data, it is necessary to minimize stress and avoid physical damage to plant tissues during the installation of the sample into the microscope. This is challenging, particularly when the whole plant is mounted as the living sample needs to be properly anchored in the microscopic system to obtain high-quality and high-resolution data. Here, we present a user-optimized sample holder EasyClick for live cell inverted confocal microscopic analysis of plant roots with diameters from 0.3 to 0.7 mm. The EasyClick holder was tested on an inverted confocal microscope using germinating plants of several cereals. Nevertheless, it can be directly used on other types of inverted microscopes from various producers and on different plant species. The EasyClick holder effectively restricts root lateral and vertical movements. This greatly improves the conditions for time-lapse microscopy of the samples of interest., (© 2023. The Author(s).)

Plant growth and morphogenesis are determined by the mechanical properties of its cell walls. Using atomic force microscopy, we have characterized the dynamics of cell wall elasticity in different tissues in developing roots of several plant species. The elongation growth zone of roots of all species studied was distinguished by a reduced modulus of elasticity of most cell walls compared to the meristem or late elongation zone. Within the individual developmental zones of roots, there were also significant differences in the elasticity of the cell walls of the different tissues, thus identifying the tissues that limit root growth in the different species. In cereals, this is mainly the inner cortex, whereas in dicotyledons this function is performed by the outer tissues-rhizodermis and cortex. These differences result in a different behaviour of the roots of these species during longitudinal dissection. Modelling of longitudinal root dissection using measured properties confirmed the difference shown. Thus, the morphogenesis of monocotyledonous and dicotyledonous roots relies on different tissues as growth limiting, which should be taken into account when analyzing the localization of associated molecular events. At the same time, no matrix polysaccharide was found whose immunolabelling in type I or type II cell walls would predict their mechanical properties. However, assessment of the degree of anisotropy of cortical microtubules showed a striking correlation with the elasticity of the corresponding cell walls in all species studied., (© 2023 Society for Experimental Biology and John Wiley & Sons Ltd.)

Climate change is increasing the frequency of extreme heat events that aggravate its negative impact on plant development and agricultural yield. Most experiments designed to study plant adaption to heat stress apply homogeneous high temperatures to both shoot and root. However, this treatment does not mimic the conditions in natural fields, where roots grow in a dark environment with a descending temperature gradient. Excessively high temperatures severely decrease cell division in the root meristem, compromising root growth, while increasing the division of quiescent center cells, likely in an attempt to maintain the stem cell niche under such harsh conditions. Here, we engineered the TGRooZ, a device that generates a temperature gradient for in vitro or greenhouse growth assays. The root systems of plants exposed to high shoot temperatures but cultivated in the TGRooZ grow efficiently and maintain their functionality to sustain proper shoot growth and development. Furthermore, gene expression and rhizosphere or root microbiome composition are significantly less affected in TGRooZ-grown roots than in high-temperature-grown roots, correlating with higher root functionality. Our data indicate that use of the TGRooZ in heat-stress studies can improve our knowledge of plant response to high temperatures, demonstrating its applicability from laboratory studies to the field., (Copyright © 2022 The Author(s). Published by Elsevier Inc. All rights reserved.)

The response of plants to magnetic fields (MF) is not fully understood. This work studies the effects of pulsed MF on the germination and growth of Allium cepa roots. Onions were exposed to 25Hz, 1.5mT, 33h. Pulsed MF was generated by a Helmholtz-type equipment that generated rectangular voltage pulses. The results showed that fewer roots grew in the specimens exposed to pulsed MF (14±6 roots on day 1 to 21±8 on day 4) than in the control groups (32±17 to 48±23) (p<0.05 Friedman). Control specimens showed a root mean length of 7±4 mm (day 1) and 24±10 mm (day 4). The specimens treated with pulsed MF showed a length of 4±2 mm (day 1), reaching 18±9 mm on day 4 (p<0.001 ANOVA). In conclusion, the exposure of Allium cepa specimens to 25Hz, 1.5mT pulsed MF during 33h produces a decrease in the germination and growth of roots.

The phytohormone abscisic acid (ABA) promotes plant tolerance to major stresses such as drought, partly by modulating growth through poorly understood mechanisms. Here, we show that ABA-triggered repression of cell proliferation in the Arabidopsis thaliana root meristem relies on the swift subcellular relocalization of SNF1-RELATED KINASE 1 (SnRK1). Under favorable conditions, the SnRK1 catalytic subunit, SnRK1α1, is enriched in the nuclei of root cells, and this is accompanied by normal cell proliferation and meristem size. Depletion of two key drivers of ABA signaling, SnRK2.2 and SnRK2.3, causes constitutive cytoplasmic localization of SnRK1α1 and reduced meristem size, suggesting that, under nonstress conditions, SnRK2s promote growth by retaining SnRK1α1 in the nucleus. In response to ABA, SnRK1α1 translocates to the cytoplasm, and this is accompanied by inhibition of target of rapamycin (TOR), decreased cell proliferation, and reduced meristem size. Blocking nuclear export with leptomycin B abrogates ABA-driven SnRK1α1 relocalization to the cytoplasm and ABA-elicited inhibition of TOR. Furthermore, fusing SnRK1α1 to an SV40 nuclear localization signal leads to defective ABA-dependent TOR repression. Altogether, we demonstrate that SnRK2-dependent changes in SnRK1α1 subcellular localization are crucial for inhibiting TOR and root growth in response to ABA. Rapid relocalization of central regulators such as SnRK1 may represent a general strategy of eukaryotic organisms to respond to environmental changes.

Roots assist plants in absorbing water and nutrients from soil. Thus, they are vital to the survival of nearly all land plants, considering that plants cannot move to seek optimal environmental conditions. Crop species with optimal root system are essential for future food security and key to improving agricultural productivity and sustainability. Root systems can be improved and bred to acquire soil resources efficiently and effectively. This can also reduce adverse environmental impacts by decreasing the need for fertilization and fresh water. Therefore, there is a need to improve and breed crop cultivars with favorable root system. However, the lack of high-throughput root phenotyping tools for characterizing root traits in situ is a barrier to breeding for root system improvement. In recent years, many breakthroughs in the measurement and analysis of roots in a root system have been made. Here, we describe the major advances in root image acquisition and analysis technologies and summarize the advantages and disadvantages of each method. Furthermore, we look forward to the future development direction and trend of root phenotyping methods. This review aims to aid researchers in choosing a more appropriate method for improving the root system., Competing Interests: The authors declare that they have no competing interests., (© 2022 Li et al.)

Mechanical impedance constrains root growth in most soils. Crop cultivation changed the impedance characteristics of native soils, through topsoil erosion, loss of organic matter, disruption of soil structure and loss of biopores. Increasing adoption of Conservation Agriculture in high-input agroecosystems is returning cultivated soils to the soil impedance characteristics of native soils, but in the low-input agroecosystems characteristic of developing nations, ongoing soil degradation is generating more challenging environments for root growth. We propose that root phenotypes have evolved to adapt to the altered impedance characteristics of cultivated soil during crop domestication. The diverging trajectories of soils under Conservation Agriculture and low-input agroecosystems have implications for strategies to develop crops to meet global needs under climate change. We present several root ideotypes as breeding targets under the impedance regimes of both high-input and low-input agroecosystems, as well as a set of root phenotypes that should be useful in both scenarios. We argue that a 'whole plant in whole soil' perspective will be useful in guiding the development of future crops for future soils., (© 2021 The Authors. Plant, Cell & Environment published by John Wiley & Sons Ltd.)

In all multicellular organisms, transcriptional networks orchestrate organ development. The Arabidopsis root, with its simple structure and indeterminate growth, is an ideal model for investigating the spatiotemporal transcriptional signatures underlying developmental trajectories. To map gene expression dynamics across root cell types and developmental time, we built a comprehensive, organ-scale atlas at single-cell resolution. In addition to estimating developmental progressions in pseudotime, we employed the mathematical concept of optimal transport to infer developmental trajectories and identify their underlying regulators. To demonstrate the utility of the atlas to interpret new datasets, we profiled mutants for two key transcriptional regulators at single-cell resolution, shortroot and scarecrow. We report transcriptomic and in vivo evidence for tissue trans-differentiation underlying a mixed cell identity phenotype in scarecrow. Our results support the atlas as a rich community resource for unraveling the transcriptional programs that specify and maintain cell identity to regulate spatiotemporal organ development., Competing Interests: Declaration of interests P.N.B. is a member of the Developmental Cell advisory board and is the co-founder and Chair of the Scientific Advisory Board of Hi Fidelity Genetics, a company that works on crop root growth., (Copyright © 2022 The Authors. Published by Elsevier Inc. All rights reserved.)

Plant ecological adaptation is associated with root traits. To clarify the differences of root traits between two dominant species, Stipa krylovii and Allium polyrhizum , under different grazing intensities (light, moderate, and heavy grazing intensities), we measured root traits, including root length, root surface area, root diameter, root volume, root tips, root bifurcations, specific root length, and specific surface area. We analyzed the root morphological patterns of tip proportion, length proportion, surface proportion and volume proportion of both species, and examined their ecological adaptation strategies under grazing. The results showed that grazing inhibited aboveground and belowground growth of S. krylovii , but promoted belowground growth of A. polyrhizum . In addition, the effects of grazing on belowground part of S. krylovii was greater than aboveground part. These results indicated that the growth of S. krylovii was maintained by the aboveground part and that of A. polyrhizum was maintained by the belowground part under grazing. Root length, root bifurcations, root surface area and root tips were the main factors affecting root traits of S. krylovii , while root length, root surface area and root volume were the main factors affecting root traits of A. polyrhizum . S. krylovii could adapt to grazing stress by increasing length proportion, surface proportion and volume proportion of diameter class of 0-0.7 mm, while A. polyrhizum by increasing the length proportion, surface proportion and volume proportion of diameter class of 1.4-1.8 mm. The study on the differences of root traits between S. krylovii and A. polyrhizum could help provide a scientific basis for controlling grassland degradation.

There are numerous exchanges of signals and materials between leaves and roots, including nitrogen, which is one of the essential nutrients for plant growth and development. In this study we identified and characterized the Chlorophyll A/B-Binding Protein ( CAB ) (named coe2 for CAB overexpression 2) mutant, which is defective in the development of chloroplasts and roots under normal growth conditions. The phenotype of coe2 is caused by a mutation in the Nitric Oxide Associated ( NOA1 ) gene that is implicated in a wide range of chloroplast functions including the regulation of metabolism and signaling of nitric oxide (NO). A transcriptome analysis reveals that expression of genes involved in metabolism and lateral root development are strongly altered in coe2 seedlings compared with WT. COE2 is expressed in hypocotyls, roots, root hairs, and root caps. Both the accumulation of NO and the growth of lateral roots are enhanced in WT but not in coe2 under nitrogen limitation. These new findings suggest that COE2-dependent signaling not only coordinates gene expression but also promotes chloroplast development and function by modulating root development and absorption of nitrogen compounds.

Root architecture can be targeted in breeding programs to develop crops with better capture of water and nutrients. In rich nations, such crops would reduce production costs and environmental pollution and, in developing nations, they would improve food security and economic development. Crops with deeper roots would have better climate resilience while also sequestering atmospheric CO 2 . Deeper rooting, which improves water and N capture, is facilitated by steeper root growth angles, fewer axial roots, reduced lateral branching, and anatomical phenotypes that reduce the metabolic cost of root tissue. Mechanical impedance, hypoxia, and Al toxicity are constraints to subsoil exploration. To improve topsoil foraging for P, K, and other shallow resources, shallower root growth angles, more axial roots, and greater lateral branching are beneficial, as are metabolically cheap roots. In high-input systems, parsimonious root phenotypes that focus on water capture may be advantageous. The growing prevalence of Conservation Agriculture is shifting the mechanical impedance characteristics of cultivated soils in ways that may favor plastic root phenotypes capable of exploiting low resistance pathways to the subsoil. Root ideotypes for many low-input systems would not be optimized for any one function, but would be resilient against an array of biotic and abiotic challenges. Root hairs, reduced metabolic cost, and developmental regulation of plasticity may be useful in all environments. The fitness landscape of integrated root phenotypes is large and complex, and hence will benefit from in silico tools. Understanding and harnessing root architecture for crop improvement is a transdisciplinary opportunity to address global challenges., (© 2021 The Authors. The Plant Journal published by Society for Experimental Biology and John Wiley & Sons Ltd.)

The effects of brassinosteroid signaling on shoot and root development have been characterized in great detail but a simple consistent positive or negative impact on a basic cellular parameter was not identified. In this study, we combined digital 3D single-cell shape analysis and single-cell mRNA sequencing to characterize root meristems and mature root segments of brassinosteroid-blind mutants and wild type. The resultant datasets demonstrate that brassinosteroid signaling affects neither cell volume nor cell proliferation capacity. Instead, brassinosteroid signaling is essential for the precise orientation of cell division planes and the extent and timing of anisotropic cell expansion. Moreover, we found that the cell-aligning effects of brassinosteroid signaling can propagate to normalize the anatomy of both adjacent and distant brassinosteroid-blind cells through non-cell-autonomous functions, which are sufficient to restore growth vigor. Finally, single-cell transcriptome data discern directly brassinosteroid-responsive genes from genes that can react non-cell-autonomously and highlight arabinogalactans as sentinels of brassinosteroid-dependent anisotropic cell expansion., (Copyright © 2021 The Authors. Published by Elsevier Inc. All rights reserved.)

Organogenesis in plants is primarily postembryonic and relies on a strict balance between cell division and cell expansion. The root is a particularly well-suited model to study cell proliferation in detail since the two processes are spatially and temporally separated for all the different tissues. In addition, the root is amenable to detailed microscopic analysis to identify cells progressing through the cell cycle. While it is clear that cell proliferation activity is restricted to the root apical meristem (RAM), understanding cell proliferation kinetics and identifying its parameters have required much effort over many years. Here, we review the main concepts, experimental settings, and findings aimed at obtaining a detailed knowledge of how cells proliferate within the RAM. The combination of novel tools, experimental strategies, and mathematical models has contributed to our current view of cell proliferation in the RAM. We also discuss several lines of research that need to be explored in the future., (© The Author(s) 2021. Published by Oxford University Press on behalf of the Society for Experimental Biology.)

Brassinosteroids (BRs) play key roles in diverse plant growth processes through a complex signaling pathway. Components orchestrating the BR signaling pathway include receptors such as kinases, transcription factors, protein kinases and phosphatases. The proper functioning of the receptor kinase BRI1 and the transcription factors BES1/BZR1 depends on their dephosphorylation by type 2A protein phosphatases (PP2A). In this work, we report that an additional phosphatase family, type one protein phosphatases (PP1), contributes to the regulation of the BR signaling pathway. Co-immunoprecipitation and BiFC experiments performed in Arabidopsis plants overexpressing durum wheat TdPP1 showed that TdPP1 interacts with dephosphorylated BES1, but not with the BRI1 receptor. Higher levels of dephosphorylated, active BES1 were observed in these transgenic lines upon BR treatment, indicating that TdPP1 modifies the BR signaling pathway by activating BES1. Moreover, ectopic expression of durum wheat TdPP1 lead to an enhanced growth of primary roots in comparison to wild-type plants in presence of BR. This phenotype corroborates with a down-regulation of the BR-regulated genes CPD and DWF4. These data suggest a role of PP1 in fine-tuning BR-driven responses, most likely via the control of the phosphorylation status of BES1.

Manganese (Mn) is an essential element for plant growth and development, but transporters required for Mn uptake have only been identified in a few plant species. Here, we functionally characterized a member of the natural resistance-associated macrophage proteins (Nramps) family, FeNramp5 in buckwheat (Fagopyrum esculentum Moench), which is known as a species well adapted to acidic soils. FeNramp5 was mainly expressed in the roots, and its expression was upregulated by the deficiency of Mn and Fe. Furthermore, spatial and tissue-specific expression analysis showed that FeNramp5 was expressed in all tissues of the basal root regions. FeNramp5-GFP protein was localized to the plasma membrane when transiently expressed in buckwheat leaf protoplast. FeNramp5 showed the transport activity for Mn2+ and Cd2+ but not for Fe2+ when expressed in yeast. Furthermore, the transport activity for Mn2+ was higher in yeast expressing FeNramp5 than in yeast expressing AtNramp1. FeNramp5 was also able to complement the phenotype of Arabidopsis atnramp1 mutant in terms of the growth and accumulation of Mn and Cd. The absolute expression level of AtNramp1 was comparable to that of FeNramp5 in the roots, but buckwheat accumulated higher Mn than Arabidopsis when grown under the same condition. Further analysis showed that at least motif B in FeNramp5 seems important for its high transport activity for Mn. These results indicate that FeNramp5 is a transporter for the uptake of Mn and Cd and its higher transport activity for Mn is probably associated with higher Mn accumulation in buckwheat., (© The Author(s) 2020. Published by Oxford University Press on behalf of Japanese Society of Plant Physiologists. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)

The phloem transport network is a major evolutionary innovation that enabled plants to dominate terrestrial ecosystems. In the growth apices, the meristems, apical stem cells continuously produce early 'protophloem'. This is easily observed in Arabidopsis root meristems, in which the differentiation of individual protophloem sieve element precursors into interconnected conducting sieve tubes is laid out in a spatio-temporal gradient. The mature protophloem eventually collapses as the neighboring metaphloem takes over its function further distal from the stem cell niche. Compared with protophloem, metaphloem ontogenesis is poorly characterized, primarily because its visualization is challenging. Here, we describe the improved TetSee protocol to investigate metaphloem development in Arabidopsis root tips in combination with a set of molecular markers. We found that mature metaphloem sieve elements are only observed in the late post-meristematic root, although their specification is initiated as soon as protophloem sieve elements enucleate. Moreover, unlike protophloem sieve elements, metaphloem sieve elements only differentiate once they have fully elongated. Finally, our results suggest that metaphloem differentiation is not directly controlled by protophloem-derived cues but rather follows a distinct, robust developmental trajectory., Competing Interests: Competing interests The authors declare no competing or financial interests., (© 2021. Published by The Company of Biologists Ltd.)

Maize root responds to nitrate by modulating its development through the coordinated action of many interacting players. Nitric oxide is produced in primary root early after the nitrate provision, thus inducing root elongation. In this study, RNA sequencing was applied to discover the main molecular signatures distinguishing the response of maize root to nitrate according to their dependency on, or independency of, nitric oxide, thus discriminating the signaling pathways regulated by nitrate through nitric oxide from those regulated by nitrate itself of by further downstream factors. A set of subsequent detailed functional annotation tools (Gene Ontology enrichment, MapMan, KEGG reconstruction pathway, transcription factors detection) were used to gain further information and the lateral root density was measured both in the presence of nitrate and in the presence of nitrate plus cPTIO, a specific NO scavenger, and compared to that observed for N-depleted roots. Our results led us to identify six clusters of transcripts according to their responsiveness to nitric oxide and to their regulation by nitrate provision. In general, shared and specific features for the six clusters were identified, allowing us to determine the overall root response to nitrate according to its dependency on nitric oxide.

The F-box protein CORONANTINE INSENSITIVE1 (COI1) serves as the receptor for the plant hormone jasmonoyl-isoleucine (JA-Ile). COI1, its co-receptors of the JASMONATE ZIM-domain (JAZ) protein family, and JA-Ile form a functional unit that regulates growth or defense mechanisms in response to various stress cues. Strikingly, COI1, but not JA-Ile, is required for susceptibility of Arabidopsis thaliana towards the soil-borne vascular pathogen Verticillium longisporum. In order to obtain marker genes for further analysis of this JA-Ile-independent COI1 function, transcriptome analysis of roots of coi1 and allene oxide synthase (aos) plants (impaired in JA biosynthesis) was performed. Intriguingly, nearly all of the genes that are differentially expressed in coi1 versus aos and wild type are constitutively more highly expressed in coi1. To support our notion that COI1 acts independently of its known downstream signaling components, coi1 plants were complemented with a COI1 variant (COI1 AA ) that is compromised in its interaction with JAZs. As expected, these plants showed only weak induction of the expression of the JA-Ile marker gene VEGETATIVE STORAGE PROTEIN2 after wounding and remained sterile. On the other hand, genes affected by COI1 but not by JA-Ile were still strongly repressed by COI1 AA . We suggest that COI1 has a potential moonlighting function that serves to repress gene expression in a JA-Ile- and JAZ-independent manner., (© 2021 The Authors. The Plant Journal published by Society for Experimental Biology and John Wiley & Sons Ltd.)

Background: Phosphorus (P) is an essential macronutrient for plant growth and development. Upon P shortage, plant responds with massive reprogramming of transcription, the Phosphate Starvation Response (PSR). In parallel, the production of strigolactones (SLs)-a class of plant hormones that regulates plant development and rhizosphere signaling molecules-increases. It is unclear, however, what the functional link is between these two processes. In this study, using tomato as a model, RNAseq was used to evaluate the time-resolved changes in gene expression in the roots upon P starvation and, using a tomato CAROTENOID CLEAVAGE DIOXYGENASES 8 (CCD8) RNAi line, what the role of SLs is in this., Results: Gene ontology (GO)-term enrichment and KEGG analysis of the genes regulated by P starvation and P replenishment revealed that metabolism is an important component of the P starvation response that is aimed at P homeostasis, with large changes occurring in glyco-and galactolipid and carbohydrate metabolism, biosynthesis of secondary metabolites, including terpenoids and polyketides, glycan biosynthesis and metabolism, and amino acid metabolism. In the CCD8 RNAi line about 96% of the PSR genes was less affected than in wild-type (WT) tomato. For example, phospholipid biosynthesis was suppressed by P starvation, while the degradation of phospholipids and biosynthesis of substitute lipids such as sulfolipids and galactolipids were induced by P starvation. Around two thirds of the corresponding transcriptional changes depend on the presence of SLs. Other biosynthesis pathways are also reprogrammed under P starvation, such as phenylpropanoid and carotenoid biosynthesis, pantothenate and CoA, lysine and alkaloids, and this also partially depends on SLs. Additionally, some plant hormone biosynthetic pathways were affected by P starvation and also here, SLs are required for many of the changes (more than two thirds for Gibberellins and around one third for Abscisic acid) in the gene expression., Conclusions: Our analysis shows that SLs are not just the end product of the PSR in plants (the signals secreted by plants into the rhizosphere), but also play a major role in the regulation of the PSR (as plant hormone)., (© 2021. The Author(s).)

Abiotic stresses, such as drought, salinity, heavy metals, variations in temperature, and ultraviolet (UV) radiation, are antagonistic to plant growth and development, resulting in an overall decrease in plant yield. These stresses have direct effects on the rhizosphere, thus severely affect the root growth, and thereby affecting the overall plant growth, health, and productivity. However, the growth-promoting rhizobacteria that colonize the rhizosphere/endorhizosphere protect the roots from the adverse effects of abiotic stress and facilitate plant growth by various direct and indirect mechanisms. In the rhizosphere, plants are constantly interacting with thousands of these microorganisms, yet it is not very clear when and how these complex root, rhizosphere, and rhizobacteria interactions occur under abiotic stresses. Therefore, the present review attempts to focus on root-rhizosphere and rhizobacterial interactions under stresses, how roots respond to these interactions, and the role of rhizobacteria under these stresses. Further, the review focuses on the underlying mechanisms employed by rhizobacteria for improving root architecture and plant tolerance to abiotic stresses.

Hydrologic shifts due to climate change will affect the cycling of carbon (C) stored in boreal peatlands. Carbon cycling in these systems is carried out by microorganisms and plants in close association. This study investigated the effects of experimentally manipulated water tables (lowered and raised) and plant functional groups on the peat and root microbiomes in a boreal rich fen. All samples were sequenced and processed for bacterial, archaeal (16S DNA genes; V4), and fungal (internal transcribed spacer 2 [ITS2]) DNA. Depth had a strong effect on microbial and fungal communities across all water table treatments. Bacterial and archaeal communities were most sensitive to the water table treatments, particularly at the 10- to 20-cm depth; this area coincides with the rhizosphere or rooting zone. Iron cyclers, particularly members of the family Geobacteraceae , were enriched around the roots of sedges, horsetails, and grasses. The fungal community was affected largely by plant functional group, especially cinquefoils. Fungal endophytes (particularly Acephala spp.) were enriched in sedge and grass roots, which may have underappreciated implications for organic matter breakdown and cycling. Fungal lignocellulose degraders were enriched in the lowered water table treatment. Our results were indicative of two main methanogen communities, a rooting zone community dominated by the archaeal family Methanobacteriaceae and a deep peat community dominated by the family Methanomicrobiaceae . IMPORTANCE This study demonstrated that roots and the rooting zone in boreal fens support organisms likely capable of methanogenesis, iron cycling, and fungal endophytic association and are directly or indirectly affecting carbon cycling in these ecosystems. These taxa, which react to changes in the water table and associate with roots and, particularly, graminoids, may gain greater biogeochemical influence, as projected higher precipitation rates could lead to an increased abundance of sedges and grasses in boreal fens.

Plant roots adapt to the mechanical constraints of the soil to grow and absorb water and nutrients. As in animal species, mechanosensitive ion channels in plants are proposed to transduce external mechanical forces into biological signals. However, the identity of these plant root ion channels remains unknown. Here, we show that Arabidopsis thaliana PIEZO1 (PZO1) has preserved the function of its animal relatives and acts as an ion channel. We present evidence that plant PIEZO1 is expressed in the columella and lateral root cap cells of the root tip, which are known to experience robust mechanical strain during root growth. Deleting PZO1 from the whole plant significantly reduced the ability of its roots to penetrate denser barriers compared to wild-type plants. pzo1 mutant root tips exhibited diminished calcium transients in response to mechanical stimulation, supporting a role of PZO1 in root mechanotransduction. Finally, a chimeric PZO1 channel that includes the C-terminal half of PZO1 containing the putative pore region was functional and mechanosensitive when expressed in naive mammalian cells. Collectively, our data suggest that Arabidopsis PIEZO1 plays an important role in root mechanotransduction and establish PIEZOs as physiologically relevant mechanosensitive ion channels across animal and plant kingdoms., Competing Interests: The authors declare no competing interest.

The Mediator multiprotein complex acts as a universal adaptor between transcription factors (TFs) and RNA polymerase II. MEDIATOR25 (MED25) has an important role in jasmonic acid (JA) signaling in Arabidopsis. However, no research has been conducted on the role of MED25 in JA signaling in rice, which is one of the most important food crops globally and is a model plant for molecular studies in other monocotyledonous species. In the present study, we isolated the loss-of function mutant of MED25, osmed25, through the map-based cloning and phenotypic complementation analysis by the introduction of OsMED25 and investigated the role of OsMED25 in JA signaling in rice. The osmed25 mutants had longer primary (seminal) roots than those of the wild-type (WT) and exhibited JA-insensitive phenotypes. S-type lateral root densities in osmed25 mutants were lower than those in the WT, whereas L-type lateral root densities in osmed25 mutants were higher than those in the WT. Furthermore, the osmed25 mutants retarded JA-regulated leaf senescence under dark-induced senescence. Mutated osmed25 protein could not interact with OsMYC2, which is a positive TF in JA signaling in rice. The expression of JA-responsive senescence-associated genes was not upregulated in response to JA in the osmed25 mutants. The results suggest that OsMED25 participates in JA-mediated root development and OsMYC2-mediated leaf senescence in rice., (Copyright © 2021 Elsevier B.V. All rights reserved.)

To illuminate the similarities and differences between wild and cultivated Sarcandra glabra (S. glabra), we performed a comprehensively study on 26 batches of cultivated S. glabra and 2 batches of wild S. glabra. Chemical constituents and distribution characteristics of roots, stems and leaves in both wild and cultivated S. glabra were investigated through UHPLC-TOF-MS method. The result revealed that there were significant differences between roots, stems and leaves in S. glabra. And the chemical contents in the root part were less or even absence than those in leaf and stem, which suggested the root organ could be excluded as medicine. Meanwhile, the chemical contents of stems and leaves in cultivated S. glabra was sightly higher than that of wild samples. Therefore, cultivated S. glabra may have a high potential for substitution of wild S. glabra without affecting its pharmaceutical properties. In summary, our study could provide important information to the molecular basis for quality control of S. glabra., (Copyright © 2021 China Pharmaceutical University. Published by Elsevier B.V. All rights reserved.)

We performed micro-X-ray fluorescence imaging of frozen-hydrated sections of a root of Pteris vittata for the first time, to the best of our knowledge, to reveal the mechanism of arsenic (As) uptake. The As distribution was successfully visualized in cross sections of different parts of the root, which showed that (i) the major pathway of As uptake changes from symplastic to apoplastic transport in the direction of root growth, and (ii) As and K have different mobilities around the stele before xylem loading, despite their similar distributions outside the stele in the cross sections. These data can reasonably explain As reduction, axially observed around the root tip in the direction of root growth and radially observed in the endodermis in the cross sections, as a consequence of the incorporation of As into the cells or symplast of the root. In addition, previous observations of As species in the midrib can be reconciled by ascribing a reduction capacity to the root cells, which implies that As reduction mechanisms at the cellular level may be an important control on the peculiar root-to-shoot transport of As in P. vittata., (© The Author(s) 2021. Published by Oxford University Press.)

Background: Despite its good salt-tolerance level, key genes and pathways involved with temporal salt response of common bermudagrass (Cynodon dactylon (L.) Pers.) have not been explored. Therefore, in this study, to understand the underlying regulatory mechanism following the different period of salt exposure, a comprehensive transcriptome analysis of the bermudagrass roots was conducted., Results: The transcripts regulated after 1 h, 6 h, or 24 h of hydroponic exposure to 200 mM NaCl in the roots of bermudagrass were investigated. Dataset series analysis revealed 16 distinct temporal salt-responsive expression profiles. Enrichment analysis identified potentially important salt responsive genes belonging to specific categories, such as hormonal metabolism, secondary metabolism, misc., cell wall, transcription factors and genes encoded a series of transporters. Weighted gene co-expression network analysis (WGCNA) revealed that lavenderblush2 and brown4 modules were significantly positively correlated with the proline content and peroxidase activity and hub genes within these two modules were further determined. Besides, after 1 h of salt treatment, genes belonging to categories such as signalling receptor kinase, transcription factors, tetrapyrrole synthesis and lipid metabolism were immediately and exclusively up-enriched compared to the subsequent time points, which indicated fast-acting and immediate physiological responses. Genes involved in secondary metabolite biosynthesis such as simple phenols, glucosinolates, isoflavones and tocopherol biosynthesis were exclusively up-regulated after 24 h of salt treatment, suggesting a slightly slower reaction of metabolic adjustment., Conclusion: Here, we revealed salt-responsive genes belonging to categories that were commonly or differentially expressed in short-term salt stress, suggesting possible adaptive salt response mechanisms in roots. Also, the distinctive salt-response pathways and potential salt-tolerant hub genes investigated can provide useful future references to explore the molecular mechanisms of bermudagrass.

Gravitropism plays a critical role in the growth and development of plants. Previous reports proposed that the disruption of the actin cytoskeleton resulted in enhanced gravitropism; however, the mechanism underlying these phenomena is still unclear. In the present study, real-time observation on the effect of Latrunculin B (Lat B), a depolymerizing agent of microfilament cytoskeleton, on gravitropism of the primary root of Arabidopsis was undertaken using a vertical stage microscope. The results indicated that Lat B treatment prevented the growth of root, and the growth rates of upper and lower flanks of the horizontally placed root were asymmetrically inhibited. The growth of the lower flank was influenced by Lat B more seriously, resulting in an increased differential growth rate between the upper and lower flanks of the root. Further analysis indicated that Lat B affected cell growth mainly in the transition and elongation zones. Briefly, the current data revealed that Lat B treatment inhibited cell elongation, especially the cells in the lower flanks of the transition and elongation zones, which finally manifested as the facilitation of gravitropic curvature of the primary root.

Global wheat ( Triticum aestivum L.) production is constrained by different biotic and abiotic stresses, which are increasing with climate change. An improved root system is essential for adaptability and sustainable wheat production. In this study, 10 pairs of near-isogenic lines (NILs)-targeting four genomic regions (GRs) on chromosome arms 4BS, 4BL, 4AS, and 7AL of hexaploid wheat-were used to phenotype root traits in a semi-hydroponic system. Seven of the 10 NIL pairs significantly differed between their isolines for 11 root traits. The NIL pairs targeting qDSI.4B.1 GR varied the most, followed by the NIL pair targeting qDT.4A.1 and QHtscc.ksu-7A GRs. For pairs 5-7 targeting qDT.4A.1 GR, pair 6 significantly differed in the most root traits. Of the 4 NIL pairs targeting qDSI.4B.1 GR, pairs 2 and 4 significantly differed in 3 and 4 root traits, respectively. Pairs 9 and 10 targeting QHtscc.ksu-7A GR significantly differed in 1 and 4 root traits, respectively. Using the wheat 90K Illumina iSelect array, we identified 15 putative candidate genes associated with different root traits in the contrasting isolines, in which two UDP-glycosyltransferase (UGT)-encoding genes, TraesCS4A02G185300 and TraesCS4A02G442700 , and a leucine-rich repeat receptor-like protein kinase (LRR-RLK)-encoding gene, TraesCS4A02G330900 , also showed important functions for root trait control in other crops. This study characterized, for the first time, that these GRs control root traits in wheat, and identified candidate genes, although the candidate genes will need further confirmation and validation for marker-assisted wheat breeding.

Similar to other complex organisms, plants consist of diverse and specialized cell types. The gain of unique biological functions of these different cell types is the consequence of the establishment of cell-type-specific transcriptional programs. As a necessary step in gaining a deeper understanding of the regulatory mechanisms controlling plant gene expression, we report the use of single-nucleus RNA sequencing (sNucRNA-seq) and single-nucleus assay for transposase accessible chromatin sequencing (sNucATAC-seq) technologies on Arabidopsis roots. The comparison of our single-nucleus transcriptomes to the published protoplast transcriptomes validated the use of nuclei as biological entities to establish plant cell-type-specific transcriptomes. Furthermore, our sNucRNA-seq results uncovered the transcriptomes of additional cell subtypes not identified by single-cell RNA-seq. Similar to our transcriptomic approach, the sNucATAC-seq approach led to the distribution of the Arabidopsis nuclei into distinct clusters, suggesting the differential accessibility of chromatin between groups of cells according to their identity. To reveal the impact of chromatin accessibility on gene expression, we integrated sNucRNA-seq and sNucATAC-seq data and demonstrated that cell-type-specific marker genes display cell-type-specific patterns of chromatin accessibility. Our data suggest that the differential chromatin accessibility is a critical mechanism to regulate gene activity at the cell-type level., (Copyright © 2021 The Authors. Published by Elsevier Inc. All rights reserved.)