OsASR5 enhances drought tolerance through a stomatal closure pathway associated with ABA and H2 O2 signalling in rice

The transcription factor TaWHY2-6A acts as a positive regulator in response to drought tolerance in transgenic plants

Drought stress severely affects wheat yield, and Whirly (WHY) transcription factors (TFs) are essential in modulating plant tolerance to abiotic stresses. In this study, we identified six WHY members in the wheat whole-genome database, categorized into Group I and Group II, with three homologous WHY genes in each group. From the four selected drought-responsive candidate genes with upregulated expression, we focused on TaWHY2-6A, which was significantly upregulated under drought stress. Under drought conditions, TaWHY2-6A transgenic Arabidopsis exhibited significantly higher chlorophyll content and better growth status compared to wild-type (WT) plants, indicating that TaWHY2-6A enhances drought resistance in transgenic Arabidopsis. In contrast, wheat lines with silenced-TaWHY2-6A exhibited a more severe wilting phenotype following drought treatment, accompanied by elevated levels of H2O2 and O2.-, and reduced antioxidant enzyme activity. These findings suggest that the wheat TaWHY2-6A gene positively regulates drought resistance under drought stress. This research provides a theoretical basis and valuable genetic resources for drought-resistance breeding in wheat.

Phenomics-assisted genetic dissection and molecular design of drought resistance in rice

Dissecting the mechanism of drought resistance (DR) and designing drought-resistant rice varieties are promising strategies to address the challenge of climate change. Here, we selected a typical drought-avoidant (DA) variety, IRAT109, and a drought-tolerant (DT) variety, Hanhui15, as parents to develop a stable recombinant inbred line (RIL) population (F8, 1262 lines). The de novo assembled genomes of both parents were released. By resequencing of the RIL population, a set of 1 189 216 reliable SNPs were obtained and used to construct a dense genetic map. Using above- and belowground phenomic platforms and multimodal cameras, we captured 139 040 image-based traits (i-traits) of whole-plant phenotypes in response to drought stress throughout the entire rice growth period and identified 32 586 drought-responsive quantitative trait loci (QTLs), including 2097 unique QTLs. QTLs associated with panicle i-traits occurred more than 600 times on the middle of chromosome 8, and QTLs associated with leaf i-traits occurred more than 800 times on the 5' end of chromosome 3, indicating the potential effects of these QTLs on plant phenotypes. We selected three candidate genes (OsMADS50, OsGhd8, OsSAUR11) related to leaf, panicle, and root traits, respectively, and verified their functions in DR. OsMADS50 was found to negatively regulate DR by modulating leaf dehydration, grain size, and downward root growth. A total of 18 and 21 composite QTLs significantly related to grain weight and plant biomass were also screened from 597 lines in the RIL population under drought conditions in field experiments, and the composite QTL regions showed substantial overlap (76.9%) with known DR gene regions. Based on three candidate DR genes, we proposed a haplotype design suitable for different environments and breeding objectives. This study provides a valuable reference for multimodal and time-series phenomic analyses, deciphers the genetic mechanisms of DA and DT rice varieties, and offers a molecular navigation map for breeding of DR varieties.

Unraveling the intricate tapestry of bamboo transcription factors in abiotic stress signaling and resilience with special reference to moso bamboo family

The abiotic stress tolerance mechanism in plants is regulated by multiple physiological, biochemical, and molecular processes; hence, omics approaches to underpin these mechanisms are essential. It is clear that transcription factors (TFs) are one of the fundamental molecular switches that play a crucial role in modulating, regulating, and orchestrating plants in response to various climatic vagaries. Several reports are available now, focusing on understanding the roles of TFs, including those in Poaceae family in regulating different biological processes and stress responses. However, research on bamboo TFs' regulatory role in providing abiotic stress tolerance is limited. Hence the present review offers innovative insights into unraveling the molecular regulation of known family of TFs in different species of bamboo which have been identified as regulators of transcript abundance in numerous genes responsive to various abiotic stresses. Additionally, this review highlights recent discoveries concerning bamboo TFs, encompassing their classification, promoter analysis and functional dynamics in response to different abiotic stresses. Attempt has also been made to delve into the molecular interplay and cross-talk among these TFs during abiotic stresses, thus proposing potential strategies for enhancing the intricate regulatory networks involved in the adaptive responses of bamboo species.

Investigation of the potential regulation of the UDP-glycosyltransferase genes on rice grain size and abiotic stress response

Uridine diphosphate (UDP) glycosyltransferases (UGTs) are widely involved in various metabolic processes. In the present study, we performed a genome-wide survey and identified 199 Oryza sativa UGT genes (OsUGTs), which were classified into 17 groups. We showed that tandem duplication played a major role in the expansion of the OsUGT family, which experienced purifying selection during the evolution process. 163 OsUGTs were expressed in at least one of the six tested tissues, and were clustered into three groups according to their tissue expression profiles. By using the RFGB database, we identified different haplotypes of seven OsUGTs that were highly expressed in seeds, and showed significant differences in grain size among different haplotypes. Moreover, our results also uncovered differential responses of OsUGTs expression to abiotic stresses and hormone treatments, including drought, salt, cold, heat, ABA, JA and AUXIN. By using quantitative real-time PCR, we further confirmed the differential expression of nine selected OsUGTs under ABA, JA, salt, drought and cold treatments, among which OsUGT5 and OsUGT182 were induced by all these five treatments. Our results provide insight into the role of several UGT genes for physiological responses, which will facilitate to investigate their function in regulating rice development and abiotic stress responses.

Rice OsDof12 enhances tolerance to drought stress by activating the phenylpropanoid pathway

Drought is a major abiotic stress that severely affects cereal production worldwide. Although several genes have been identified that enhance the ability of rice to withstand drought stress, further research is needed to fully understand the molecular mechanisms underlying the response to drought stress. Our study showed that overexpression of rice DNA binding with one finger 12 (OsDof12) enhances tolerance to drought stress. Rice plants overexpressing OsDof12 (OsDof12-OE) displayed significantly higher tolerance to drought stress than the parental japonica rice "Dongjin". Transcriptome analysis revealed that many genes involved in phenylpropanoid biosynthesis were upregulated in OsDof12-OE plants, including phenylalanine ammonia-lyase 4 (OsPAL4), OsPAL6, cinnamyl alcohol dehydrogenase 6 (CAD6), and 4-coumarate-coA ligase like 6 (4CLL6). Accordingly, this transcriptional alteration led to the substantial accumulation of phenolic compounds, such as sinapic acids, in the leaves of OsDof12-OE plants, effectively lowering the levels of reactive oxygen species. Notably, OsDof12 bound to the AAAG-rich core sequence of the OsPAL4 promoter and promoted transcription. In addition, GIGANTEA (OsGI) interacts with OsDof12 in the nucleus and attenuates the transactivation activity of OsDof12 on OsPAL4. Our findings reveal a novel role for OsDof12 in promoting phenylpropanoid-mediated tolerance to drought stress.

The ubiquitin E3 ligase RZFP1 affects drought tolerance in poplar by mediating the degradation of the protein phosphatase PP2C-9

Abscisic acid (ABA) signaling has been implicated in plant responses to water deficit-induced osmotic stress. However, the underlying molecular mechanism remains unelucidated. This study identified the RING-type E3 ubiquitin ligase RING ZINC FINGER PROTEIN1 (PtrRZFP1) in poplar (Populus trichocarpa), a woody model plant. PtrRZFP1 encodes an ubiquitin E3 ligase that participates in protein ubiquitination. PtrRZFP1 mainly functions in the nucleus and endoplasmic reticulum and is activated by drought and ABA. PtrRZFP1-overexpressing transgenic poplars (35S:PtrRZFP1) showed greater tolerance to drought, whereas PtrRZFP1-knockdown lines (KD-PtrRZFP1) showed greater sensitivity to drought. Under treatment with polyethylene glycol and ABA, PtrRZFP1 promoted the production of nitric oxide and hydrogen peroxide in stomatal guard cells, ultimately enhancing stomatal closure and improving drought tolerance. Additionally, PtrRZFP1 physically interacted with the clade A Protein Phosphatase 2C protein PtrPP2C-9, a core regulator of ABA signaling, and mediated its ubiquitination and eventual degradation through the ubiquitination-26S proteasome system, indicating that PtrRZFP1 positively regulates the ABA signaling pathway. Furthermore, the PtrPP2C-9-overexpression line was insensitive to ABA and more sensitive to drought than the wild-type plants, whereas the opposite phenotype was observed in 35S:PtrRZFP1 plants. In general, PtrRZFP1 negatively regulates the stability of PtrPP2C-9 to mediate poplar drought tolerance. The results of this study provide a theoretical framework for the targeted breeding of drought-tolerant traits in perennial woody plants.

Genome-wide associated study identifies FtPMEI13 gene conferring drought resistance in Tartary buckwheat

Tartary buckwheat is known for its ability to adapt to intricate growth conditions and to possess robust stress-resistant properties. Nevertheless, it remains vulnerable to drought stress, which can lead to reduced crop yield. To identify potential genes involved in drought resistance, a genome-wide association study on drought tolerance in Tartary buckwheat germplasm was conducted. A gene encoding pectin methylesterase inhibitors protein (FtPMEI13) was identified, which is not only associated with drought tolerance but also showed induction during drought stress and abscisic acid (ABA) treatment. Further analysis revealed that overexpression of FtPMEI13 leads to improved drought tolerance by altering the activities of antioxidant enzymes and the levels of osmotically active metabolites. Additionally, FtPMEI13 interacts with pectin methylesterase (PME) and inhibits PME activity in response to drought stress. Our results suggest that FtPMEI13 may inhibit the activity of FtPME44/FtPME61, thereby affecting pectin methylesterification in the cell wall and modulating stomatal closure in response to drought stress. Yeast one-hybrid, dual-luciferase assays, and electrophoretic mobility shift assays demonstrated that an ABA-responsive transcription factor FtbZIP46, could bind to the FtPMEI13 promoter, enhancing FtPMEI13 expression. Further analysis indicated that Tartary buckwheat accessions with the genotype resulting in higher FtPMEI13 and FtbZIP46 expression exhibited higher drought tolerance compared to the others. This suggests that this genotype has potential for application in Tartary buckwheat breeding. Furthermore, the natural variation of FtPMEI13 was responsible for decreased drought tolerance during Tartary buckwheat domestication. Taken together, these results provide basic support for Tartary buckwheat breeding for drought tolerance.

The transcription factor TabZIP156 acts as a positive regulator in response to drought tolerance in Arabidopsis and wheat (Triticum aestivum L.)

Drought stress strongly restricts the growth, development, and yield of wheat worldwide. Among the various transcription factors (TFs) involved in the wheat drought response, the specific functions of many basic leucine zipper (bZIP) TFs related to drought tolerance are still not well understood. In this study, we focused on the bZIP TF TabZIP156 in wheat. Our analysis showed that TabZIP156 was highly expressed in both roots and leaves, and it responded to drought and abscisic acid (ABA) stress. Through subcellular localization and transactivation assays, we confirmed that TabZIP156 was located to the nucleus and functioned as a transcriptional activator. Overexpression of TabZIP156 in Arabidopsis enhanced drought tolerance, as evidenced by higher germination rate, longer root length, lower water loss rate, reduced ion leakage, increased proline accumulation, decreased levels of H2O2, O2- and MDA, and improved activities of POD, SOD, and CAT enzymes. Additionally, the expression of drought- and antioxidant-related genes were significantly upregulated in TabZIP156 transgenic Arabidopsis under drought stress. However, silencing TabZIP156 in wheat led to decreased proline content, increased accumulation of H2O2, O2- and MDA, reduced activities of antioxidant enzymes, and downregulation of many drought- and antioxidant-related genes under drought stress. Furthermore, the dual-luciferase assay demonstrated that TabZIP156 could activate the expression of TaP5CS, TaDREB1A, and TaPOD by binding to their promoters. Taken together, this study highlights the significant role of TabZIP156 in drought stress and provides valuable insights for its potential application in breeding drought-resistant wheat.

Abscisic acid-, stress-, ripening-induced 2 like protein, TaASR2L, promotes wheat resistance to stripe rust

Wheat stripe rust, caused by Puccinia striiformis f. sp. tritici (Pst), is one of the most destructive wheat diseases. The plant hormone abscisic acid (ABA) plays a key regulatory role in plant response to stress. ABA-, stress-, ripening-induced proteins (ASR) have been shown to be abundantly induced in response to biotic and abiotic stresses to protect plants from damage. However, the function of wheat ASR2-like protein (TaASR2L) in plants under biotic stress remains unclear. In this study, transient silencing of TaASR2L using a virus-induced gene silencing system substantially reduced wheat resistance to Pst. TaASR2L interaction with serine/arginine-rich splicing factor SR30-like (TaSR30) was validated mainly in the nucleus. Knockdown of TaSR30 expression substantially reduced wheat resistance to Pst. Overexpression of TaASR2L and TaSR30 demonstrated that they can promote the expression of ABA- and resistance-related genes to enhance wheat resistance to Pst. In addition, the expression levels of TaSR30 and TaASR2L were substantially increased by exogenous ABA, and the resistance of wheat to Pst was increased, and the expression of PR genes was induced. Therefore, these results suggest that TaASR2L interacts with TaSR30 by promoting PR genes expression and enhancing wheat resistance to Pst.

Profiling of Key Hub Genes Using a Two-State Weighted Gene Co-Expression Network of 'Jao Khao' Rice under Soil Salinity Stress Based on Time-Series Transcriptome Data

RNA-sequencing enables the comprehensive detection of gene expression levels at specific time points and facilitates the identification of stress-related genes through co-expression network analysis. Understanding the molecular mechanisms and identifying key genes associated with salt tolerance is crucial for developing rice varieties that can thrive in saline environments, particularly in regions affected by soil salinization. In this study, we conducted an RNA-sequencing-based time-course transcriptome analysis of 'Jao Khao', a salt-tolerant Thai rice variety, grown under normal or saline (160 mM NaCl) soil conditions. Leaf samples were collected at 0, 3, 6, 12, 24, and 48 h. In total, 36 RNA libraries were sequenced. 'Jao Khao' was found to be highly salt-tolerant, as indicated by the non-significant differences in relative water content, cell membrane stability, leaf greenness, and chlorophyll fluorescence over a 9-day period under saline conditions. Plant growth was slightly retarded during days 3-6 but recovered by day 9. Based on time-series transcriptome data, we conducted differential gene expression and weighted gene co-expression network analyses. Through centrality change from normal to salinity network, 111 key hub genes were identified among 1,950 highly variable genes. Enriched genes were involved in ATP-driven transport, light reactions and response to light, ATP synthesis and carbon fixation, disease resistance and proteinase inhibitor activity. These genes were upregulated early during salt stress and RT-qPCR showed that 'Jao Khao' exhibited an early upregulation trend of two important genes in energy metabolism: RuBisCo (LOC_Os10g21268) and ATP synthase (LOC_Os10g21264). Our findings highlight the importance of managing energy requirements in the initial phase of the plant salt-stress response. Therefore, manipulation of the energy metabolism should be the focus in plant resistance breeding and the genes identified in this work can serve as potentially effective candidates.

A module involving HIGH LEAF TEMPERATURE1 controls instantaneous water use efficiency

Drought stress inhibits plant growth and agricultural production. Improving plant instantaneous water use efficiency (iWUE), which is strictly regulated by stomata, is an effective way to cope with drought stress. However, the mechanisms of iWUE regulation are poorly understood. Through genetic screening for suppressors of mpk12-4, an Arabidopsis (Arabidopsis thaliana) mutant with a major iWUE quantitative trait locus gene MITOGEN-ACTIVATED PROTEIN KINASE12 deleted, we identified HIGH LEAF TEMPERATURE1 (HT1). Genetic interaction and physiological analyses showed that MPK12 controls iWUE through multiple modules in a high CO2-induced stomatal closing pathway that regulate SLOW ANION CHANNEL-ASSOCIATED1 (SLAC1) activity. HT1 acts downstream of MPK12, whereas OPEN STOMATA1 (OST1) and GUARD CELL HYDROGEN PEROXIDE-RESISTANT1 (GHR1) function downstream of HT1 by activating SLAC1 in iWUE. Photosynthetic-CO2 response curves and biomass analyses under different water-supply conditions showed that HT1 dysfunction improved iWUE and also increased plant growth capacity, and products of HT1 putative orthologs from Brassica (Brassica napus) and rice (Oryza sativa) exhibited functions similar to that of Arabidopsis HT1 in iWUE and the CO2-signaling pathway. Our study revealed the mechanism of MPK12-mediated iWUE regulation in Arabidopsis and provided insight into the internal relationship between iWUE and CO2 signaling in guard cells and a potential target for improving crop iWUE and drought tolerance.

Development History, Structure, and Function of ASR (Abscisic Acid-Stress-Ripening) Transcription Factor

Abiotic and biotic stress factors seriously affect plant growth and development. The process of plant response to abiotic stress involves the synergistic action of multiple resistance genes. The ASR (Abscisic acid stress-ripening) gene is a plant-specific transcription factor that plays a central role in regulating plant senescence, fruit ripening, and response to abiotic stress. ASR family members are highly conserved in plant evolution and contain ABA/WBS domains. ASR was first identified and characterized in tomatoes (Solanum lycopersicum L.). Subsequently, the ASR gene has been reported in many plant species, extending from gymnosperms to monocots and dicots, but lacks orthologues in Arabidopsis (Arabidopsis thaliana). The promoter regions of ASR genes in most species contain light-responsive elements, phytohormone-responsive elements, and abiotic stress-responsive elements. In addition, ASR genes can respond to biotic stresses via regulating the expression of defense genes in various plants. This review comprehensively summarizes the evolutionary history, gene and protein structures, and functions of the ASR gene family members in plant responses to salt stress, low temperature stress, pathogen stress, drought stress, and metal ions, which will provide valuable references for breeding high-yielding and stress-resistant plant varieties.

Adaptation of the Invasive Plant Sphagneticola trilobata (L.) Pruski to Drought Stress

Invasive species and their hybrids with native species threaten biodiversity. However, there are few reports on the drought stress adaptability of invasive species Sphagneticola trilobata (L.) Pruski and its hybrid with native species S. calendulacea. In this study, relative water content (RWC), abscisic acid (ABA), reactive oxygen species, antioxidant capacity, and photosynthetic capacity were measured in the hybrid and its parents under drought stress (13% PEG-6000). Under drought stress, the ABA content and RWC in S. trilobata were the highest. RWC decreased by 28% in S. trilobata, 41% in S. calendulacea, and 33% in the hybrid. Activities of the antioxidant enzymes in S. trilobata were the highest, and the accumulation of malondialdehyde (MDA) was the lowest (4.3 μg g-1), while it was the highest in S. calendulacea (6.9 μg g-1). The maximum photochemical efficiency (Fv/Fm) of S. calendulacea was the lowest (0.71), and it was the highest in S. trilobata (7.5) at 8 h under drought stress. The results suggest that the drought resistance of the hybrid was weaker than that of S. trilobata but stronger than that of S. calendulacea. Therefore, the survival of S. calendulacea may be threatened by both the invasive species S. trilobata and the hybrid.

Spatiotemporal transcriptomic atlas of rhizome formation in Oryza longistaminata

Rhizomes are modified stems that grow underground and produce new individuals genetically identical to the mother plant. Recently, a breakthrough has been made in efforts to convert annual grains into perennial ones by utilizing wild rhizomatous species as donors, yet the developmental biology of this organ is rarely studied. Oryza longistaminata, a wild rice species featuring strong rhizomes, provides a valuable model for exploration of rhizome development. Here, we first assembled a double-haplotype genome of O. longistaminata, which displays a 48-fold improvement in contiguity compared to the previously published assembly. Furthermore, spatiotemporal transcriptomics was performed to obtain the expression profiles of different tissues in O. longistaminata rhizomes and tillers. Two spatially reciprocal cell clusters, the vascular bundle 2 cluster and the parenchyma 2 cluster, were determined to be the primary distinctions between the rhizomes and tillers. We also captured meristem initiation cells in the sunken area of parenchyma located at the base of internodes, which is the starting point for rhizome initiation. Trajectory analysis further indicated that the rhizome is regenerated through de novo generation. Collectively, these analyses revealed a spatiotemporal transcriptional transition underlying the rhizome initiation, providing a valuable resource for future perennial crop breeding.

ZmASR1 negatively regulates drought stress tolerance in maize

Abscisic acid-, stress-, and ripening-induced (ASR) proteins in plants play a significant role in plant response to diverse abiotic stresses. However, the functions of ASR genes in maize remain unclear. In the present study, we identified a novel drought-induced ASR gene in maize (ZmASR1) and functionally characterized its role in mediating drought tolerance. The transcription of ZmASR1 was upregulated under drought stress and abscisic acid (ABA) treatment, and the ZmASR1 protein was observed to exhibit nuclear and cytoplasmic localization. Moreover, ZmASR1 knockout lines generated with the CRISPR-Cas9 system showed lower ROS accumulation, higher ABA content, and a higher degree of stomatal closure than wild-type plants, leading to higher drought tolerance. Transcriptome sequencing data indicated that the significantly differentially expressed genes in the drought treatment group were mainly enriched in ABA signal transduction, antioxidant defense, and photosynthetic pathway. Taken together, the findings suggest that ZmASR1 negatively regulates drought tolerance and represents a candidate gene for genetic manipulation of drought resistance in maize.

A long non-coding RNA functions as a competitive endogenous RNA to modulate TaNAC018 by acting as a decoy for tae-miR6206

Increasing evidence indicates a strong correlation between the deposition of cuticular waxes and drought tolerance. However, the precise regulatory mechanism remains elusive. Here, we conducted a comprehensive transcriptome analysis of two wheat (Triticum aestivum) near-isogenic lines, the glaucous line G-JM38 rich in cuticular waxes and the non-glaucous line NG-JM31. We identified 85,143 protein-coding mRNAs, 4,485 lncRNAs, and 1,130 miRNAs. Using the lncRNA-miRNA-mRNA network and endogenous target mimic (eTM) prediction, we discovered that lncRNA35557 acted as an eTM for the miRNA tae-miR6206, effectively preventing tae-miR6206 from cleaving the NAC transcription factor gene TaNAC018. This lncRNA-miRNA interaction led to higher transcript abundance for TaNAC018 and enhanced drought-stress tolerance. Additionally, treatment with mannitol and abscisic acid (ABA) each influenced the levels of tae-miR6206, lncRNA35557, and TaNAC018 transcript. The ectopic expression of TaNAC018 in Arabidopsis also improved tolerance toward mannitol and ABA treatment, whereas knocking down TaNAC018 transcript levels via virus-induced gene silencing in wheat rendered seedlings more sensitive to mannitol stress. Our results indicate that lncRNA35557 functions as a competing endogenous RNA to modulate TaNAC018 expression by acting as a decoy target for tae-miR6206 in glaucous wheat, suggesting that non-coding RNA has important roles in the regulatory mechanisms responsible for wheat stress tolerance.

OsNAC120 balances plant growth and drought tolerance by integrating GA and ABA signaling in rice

The crosstalk between gibberellin (GA) and abscisic acid (ABA) signaling is crucial for balancing plant growth and adaption to environmental stress. Nevertheless, the molecular mechanism of their mutual antagonism still remains to be fully clarified. In this study, we found that knockout of the rice NAC (NAM, ATAF1/2, CUC2) transcription factor gene OsNAC120 inhibits plant growth but enhances drought tolerance, whereas OsNAC120 overexpression produces the opposite results. Exogenous GA can rescue the semi-dwarf phenotype of osnac120 mutants, and further study showed that OsNAC120 promotes GA biosynthesis by transcriptionally activating the GA biosynthetic genes OsGA20ox1 and OsGA20ox3. The DELLA protein SLENDER RICE1 (SLR1) interacts with OsNAC120 and impedes its transactivation ability, and GA treatment can remove the inhibition of transactivation activity caused by SLR1. On the other hand, OsNAC120 negatively regulates rice drought tolerance by repressing ABA-induced stomatal closure. Mechanistic investigation revealed that OsNAC120 inhibits ABA biosynthesis via transcriptional repression of the ABA biosynthetic genes OsNCED3 and OsNCED4. Rice OSMOTIC STRESS/ABA-ACTIVATED PROTEIN KINASE 9 (OsSAPK9) physically interacts with OsNAC120 and mediates its phosphorylation, which results in OsNAC120 degradation. ABA treatment accelerates OsNAC120 degradation and reduces its transactivation activity. Together, our findings provide evidence that OsNAC120 plays critical roles in balancing GA-mediated growth and ABA-induced drought tolerance in rice. This research will help us to understand the mechanisms underlying the trade-off between plant growth and stress tolerance and to engineer stress-resistant, high-yielding crops.

Decoding the effects of drought stress on popcorn (Zea mays var. everta) flowering combining proteomics and physiological analysis

Under conditions of soil water limitation and adequate irrigation, we conducted an investigation into the growth dynamics, gas exchange performance, and proteomic profiles of two inbred popcorn lines-L71, characterized as drought-tolerant, and L61, identified as drought-sensitive. Our goal was to uncover the mechanisms associated with tolerance to soil water limitation during the flowering. The plants were cultivated until grain filling in a substrate composed of perlite and peat within 150cm long lysimeter, subjected to two water conditions (WC): i) irrigated (WW) at lysimeter capacity (LC - 100%), and ii) water-stressed (WS). Under WS conditions, the plants gradually reached 45% of LC and were maintained at this level for 10 days. Irrespective of the WC, L71 exhibited the highest values of dry biomass in both shoot and root systems, signifying its status as the most robust genotype. The imposed water limitation led to early senescence, chlorophyll degradation, and increased anthocyanin levels, with a more pronounced impact observed in L61. Traits related to gas exchange manifested differences between the lines only under WS conditions. A total of 1838 proteins were identified, with 169 differentially accumulated proteins (DAPs) in the tolerant line and 386 DAPs in the sensitive line. Notably, differences in energy metabolism, photosynthesis, oxidative stress response, and protein synthesis pathways were identified as the key distinctions between L71 and L61. Consequently, our findings offer valuable insights into the alterations in proteomic profiles associated with the adaptation to soil water limitation in popcorn.

Molecular Mechanisms and Regulatory Pathways Underlying Drought Stress Response in Rice

Rice is a staple food for 350 million people globally. Its yield thus affects global food security. Drought is a serious environmental factor affecting rice growth. Alleviating the inhibition of drought stress is thus an urgent challenge that should be solved to enhance rice growth and yield. This review details the effects of drought on rice morphology, physiology, biochemistry, and the genes associated with drought stress response, their biological functions, and molecular regulatory pathways. The review further highlights the main future research directions to collectively provide theoretical support and reference for improving drought stress adaptation mechanisms and breeding new drought-resistant rice varieties.

Protein Disorder in Plant Stress Adaptation: From Late Embryogenesis Abundant to Other Intrinsically Disordered Proteins

Global climate change has caused severe abiotic and biotic stresses, affecting plant growth and food security. The mechanical understanding of plant stress responses is critical for achieving sustainable agriculture. Intrinsically disordered proteins (IDPs) are a group of proteins without unique three-dimensional structures. The environmental sensitivity and structural flexibility of IDPs contribute to the growth and developmental plasticity for sessile plants to deal with environmental challenges. This article discusses the roles of various disordered proteins in plant stress tolerance and resistance, describes the current mechanistic insights into unstructured proteins such as the disorder-to-order transition for adopting secondary structures to interact with specific partners (i.e., cellular membranes, membrane proteins, metal ions, and DNA), and elucidates the roles of liquid-liquid phase separation driven by protein disorder in stress responses. By comparing IDP studies in animal systems, this article provides conceptual principles of plant protein disorder in stress adaptation, reveals the current research gaps, and advises on the future research direction. The highlighting of relevant unanswered questions in plant protein disorder research aims to encourage more studies on these emerging topics to understand the mechanisms of action behind their stress resistance phenotypes.

Maize ZmBES1/BZR1-1 transcription factor negatively regulates drought tolerance

Drought stress is a common abiotic factor and restricts plant growth and development. Exploring maize stress-related genes and their regulatory mechanisms is crucial for ensuring agricultural productivity and food security. The BRI1-EMS1 suppressor (BES1)/brassinazole-resistant 1 (BZR1) transcription factors (TFs) play important roles in plant growth, development, and stress response. However, maize ZmBES1/BZR1s are rarely reported. In the present study, the ZmBES1/BZR1-1 gene was cloned from maize B73 and functionally characterized in transgenic Arabidopsis and rice in drought stress response. The ZmBES1/BZR1-1 protein possessed a conserved bHLH domain characterized by BES1/BZR1 TFs, localized in the nucleus, and showed transcription activation activity. The expression of ZmBES1/BZR1-1 exhibited no tissue specificity but drought-inhibitory expression in maize. Under drought stress, overexpression of ZmBES1/BZR1-1 resulted in the enhancement of drought sensitivity of transgenic Arabidopsis and rice with a lower survival rate, reactive oxygen species (ROS) level and relative water content (RWC) and a higher stomatal aperture and relative electrolyte leakage (REL). The RNA-seq results showed that 56 differentially expressed genes (DEGs) were regulated by ZmBES1/BZR1-1 by binding to E-box elements in their promoters. The GO analysis showed that the DEGs were significantly annotated with response to oxidative stress and oxygen level. The study suggests that the ZmBES1/BZR1-1 gene negatively regulates drought stress, which provides insights into further underlying molecular mechanisms in the drought stress response mediated by BZR1/BES1s.

Identification of the Abscisic Acid-, Stress-, and Ripening-Induced (ASR) Family Involved in the Adaptation of Tetragonia tetragonoides (Pall.) Kuntze to Saline-Alkaline and Drought Habitats

Tetragonia tetragonoides (Pall.) Kuntze (Aizoaceae, 2n = 2x = 32), a vegetable used for both food and medicine, is a halophyte that is widely distributed in the coastal areas of the tropics and subtropics. Saline-alkaline soils and drought stress are two major abiotic stressors that significantly affect the distribution of tropical coastal plants. Abscisic acid-, stress-, and ripening-induced (ASR) proteins belong to a family of plant-specific, small, and hydrophilic proteins with important roles in plant development, growth, and abiotic stress responses. Here, we characterized the ASR gene family from T. tetragonoides, which contained 13 paralogous genes, and divided TtASRs into two subfamilies based on the phylogenetic tree. The TtASR genes were located on two chromosomes, and segmental duplication events were illustrated as the main duplication method. Additionally, the expression levels of TtASRs were induced by multiple abiotic stressors, indicating that this gene family could participate widely in the response to stress. Furthermore, several TtASR genes were cloned and functionally identified using a yeast expression system. Our results indicate that TtASRs play important roles in T. tetragonoides' responses to saline-alkaline soils and drought stress. These findings not only increase our understanding of the role ASRs play in mediating halophyte adaptation to extreme environments but also improve our knowledge of plant ASR protein evolution.

Water-saving techniques: physiological responses and regulatory mechanisms of crops

Water-saving irrigation techniques play a crucial role in addressing water scarcity challenges and promoting sustainable agriculture. However, the selection of appropriate water-saving irrigation methods remains a challenge in agricultural production. Additionally, the molecular regulatory mechanisms of crops under water-saving irrigation are not yet clear. This review summarizes the latest research developments in the application of different water-saving irrigation technologies to five important crops (rice, wheat, soybeans, maize, and cotton). It provides an overview of the impact of different irrigation techniques on crop yield, water use efficiency (WUE), physiology, growth, and environmental effects. Additionally, the review compares and contrasts the molecular regulatory mechanisms of crops under water-saving irrigation techniques with those under traditional drought stress, emphasizing the significance of combining irrigation technologies with genetic engineering for developing drought-resistant varieties and improving WUE. Furthermore, the integration of various technologies can stimulate new management strategies, optimize water resource utilization, and enhance sustainability, representing a major focus for future research. In conclusion, this review underscores the importance of water-saving irrigation technologies, especially when combined with genetic engineering, in addressing water resource scarcity, increasing crop yields, and promoting sustainable agriculture.

A novel Pinellia ternata catalase gene PtCAT2 regulates drought tolerance in Arabidopsis by modulating ROS balance

Drought is one of the major abiotic stresses limiting agricultural production, particularly for shallow-rooted plants like Pinellia ternata. It damages plants via oxidative burst, but this effect could be mitigated by catalase (CAT). However, no studies have been reported on CAT homologs in P. ternata, a drought-sensitive plant species. In the present study, a novel CAT gene, PtCAT2, was functionally characterized via overexpression in Arabidopsis and analysis of cis-elements in its promoter. The isolated CAT gene was 1479 bp and encoded a protein containing 242 amino acids. The protein contains the CAT activity motif and the heme-binding site of a typical CAT, and the subcellular analysis indicated that the protein localizes at the cytoplasm and membrane. Moreover, the quantitative real-time reverse transcription PCR indicated that PtCAT2 is expressed ubiquitously in P. ternata and is strongly induced by drought stress and abscisic acid (ABA) signals. PtCAT2 overexpression enhanced the drought tolerance of Arabidopsis, as shown by the 30% increase in plant survival and a five-fold- increase in CAT activity. Moreover, PtCAT2-transgenic plants increased superoxide dismutase and peroxidase activities and reduced malondialdehyde, membrane leakage, and hydrogen peroxide (H2O2) (P<0.05). Furthermore, PtCAT2-transgenic plants showed higher tolerance to oxidative stress caused by exogenous H2O2 and retained higher chlorophyll and water contents than the WT. The mitochondria function was better maintained as presented by the higher oxygen consumption rate in transgenics under drought stress (P<0.05). The endogenous CATs and drought response-related genes were also upregulated in transgenic lines under drought stress, indicating that PtCAT2 confers drought stress tolerance by enhancing the H2O2 scavenging ability of plants to maintain their membrane integrity. These results improve our understanding of the drought response mechanisms and provide a potential breeding strategy for P. ternata genetic improvement.

Reactive Oxygen Species: A Crosslink between Plant and Human Eukaryotic Cell Systems

Reactive oxygen species (ROS) are important regulating factors that play a dual role in plant and human cells. As the first messenger response in organisms, ROS coordinate signals in growth, development, and metabolic activity pathways. They also can act as an alarm mechanism, triggering cellular responses to harmful stimuli. However, excess ROS cause oxidative stress-related damage and oxidize organic substances, leading to cellular malfunctions. This review summarizes the current research status and mechanisms of ROS in plant and human eukaryotic cells, highlighting the differences and similarities between the two and elucidating their interactions with other reactive substances and ROS. Based on the similar regulatory and metabolic ROS pathways in the two kingdoms, this review proposes future developments that can provide opportunities to develop novel strategies for treating human diseases or creating greater agricultural value.

Drought stress in rice: morpho-physiological and molecular responses and marker-assisted breeding

Rice (Oryza Sativa L.) is an essential constituent of the global food chain. Drought stress significantly diminished its productivity and threatened global food security. This review concisely discussed how drought stress negatively influenced the rice's optimal growth cycle and altered its morpho-physiological, biochemical, and molecular responses. To withstand adverse drought conditions, plants activate their inherent drought resistance mechanism (escape, avoidance, tolerance, and recovery). Drought acclimation response is characterized by many notable responses, including redox homeostasis, osmotic modifications, balanced water relations, and restored metabolic activity. Drought tolerance is a complicated phenomenon, and conventional breeding strategies have only shown limited success. The application of molecular markers is a pragmatic technique to accelerate the ongoing breeding process, known as marker-assisted breeding. This review study compiled information about quantitative trait loci (QTLs) and genes associated with agronomic yield-related traits (grain size, grain yield, harvest index, etc.) under drought stress. It emphasized the significance of modern breeding techniques and marker-assisted selection (MAS) tools for introgressing the known QTLs/genes into elite rice lines to develop drought-tolerant rice varieties. Hence, this study will provide a solid foundation for understanding the complex phenomenon of drought stress and its utilization in future crop development programs. Though modern genetic markers are expensive, future crop development programs combined with conventional and MAS tools will help the breeders produce high-yielding and drought-tolerant rice varieties.

Overexpression of a rice Tubby-like protein-encoding gene, OsFBT4, confers tolerance to abiotic stresses

The OsFBT4 belongs to a small sub-class of rice F-box proteins called TLPs (Tubby-like proteins) containing the conserved N-terminal F-box domain and a C-terminal Tubby domain. These proteins have largely been implicated in both abiotic and biotic stress responses, besides developmental roles in plants. Here, we investigated the role of OsFBT4 in abiotic stress signalling. The OsFBT4 transcript was strongly upregulated in response to different abiotic stresses in rice, including exogenous ABA. When ectopically expressed, in Arabidopsis, under a constitutive CaMV 35S promoter, the overexpression (OE) caused hypersensitivity to most abiotic stresses, including ABA, during seed germination and early seedling growth. At the 5-day-old seedling growth stage, the OE conferred tolerance to all abiotic stresses. The OE lines displayed significant tolerance to salinity and water deficit at the mature growth stage. The stomatal size and density were seen to be altered in the OE lines, accompanied by hypersensitivity to ABA and hydrogen peroxide (H₂O₂) and a reduced water loss rate. Overexpression of OsFBT4 caused upregulation of several ABA-regulated/independent stress-responsive genes at more advanced stages of growth, showing wide and intricate roles played by OsFBT4 in stress signalling. The OsFBT4 showed interaction with several OSKs (Oryza SKP1 proteins) and localized to the plasma membrane (PM). The protein translocates to the nucleus, in response to oxidative and osmotic stresses, but failed to show transactivation activity in the yeast system. The OE lines also displayed morphological deviations from the wild-type (WT) plants, suggesting a role of the gene also in plant development.

Recent Molecular Aspects and Integrated Omics Strategies for Understanding the Abiotic Stress Tolerance of Rice

Rice is an important staple food crop for over half of the world's population. However, abiotic stresses seriously threaten rice yield improvement and sustainable production. Breeding and planting rice varieties with high environmental stress tolerance are the most cost-effective, safe, healthy, and environmentally friendly strategies. In-depth research on the molecular mechanism of rice plants in response to different stresses can provide an important theoretical basis for breeding rice varieties with higher stress resistance. This review presents the molecular mechanisms and the effects of various abiotic stresses on rice growth and development and explains the signal perception mode and transduction pathways. Meanwhile, the regulatory mechanisms of critical transcription factors in regulating gene expression and important downstream factors in coordinating stress tolerance are outlined. Finally, the utilization of omics approaches to retrieve hub genes and an outlook on future research are prospected, focusing on the regulatory mechanisms of multi-signaling network modules and sustainable rice production.

Overexpression of the maize genes ZmSKL1 and ZmSKL2 positively regulates drought stress tolerance in transgenic Arabidopsis

Overexpression in Arabidopsis of the maize shikimate kinase-like genes SKL1 and SKL2 enhances tolerance to drought stress. The shikimate pathway has been reported to play an important role in plant signaling, reproduction, and development. However, its role in abiotic stress has not yet been reported. Here, two shikimate kinase-like genes, SKL1 and SKL2, were cloned from maize and their functions in mediating drought tolerance were investigated. Transcript levels of ZmSKL1 and ZmSKL2 in roots and leaves were strongly induced by drought stress. Both proteins were localized in the chloroplast. Furthermore, compared to the wild-type, transgenic Arabidopsis plants overexpressing ZmSKL1 or ZmSKL2 exhibited improved drought stress tolerance through increases in relative water content and stomatal closure. Additionally, the transgenic lines showed reduced accumulation of reactive oxygen species as a results of increased antioxidant enzyme activity. Interestingly, overexpression of ZmSKL1 or ZmSKL2 also increased sensitivity to exogenous abscisic acid. In addition, the ROS-related and stress-responsive genes were activated in transgenic lines under drought stress. Moreover, ZmSKL1 and ZmSKL2 were found to separately interact with ZmASR3, which is an important regulatory protein in mediating drought tolerance, suggesting that ZmSKL1 and ZmSKL2, together with ZmASR3, are proteins that may confer drought tolerance as candidates in plant genetic breeding manipulations.

HaASR2 from Haloxylon ammodendron confers drought and salt tolerance in plants

Abscisic acid (ABA), stress, and ripening-induced proteins (ASR), which belong to the ABA/WDS domain superfamily, are involved in the plant response to abiotic stresses. Haloxylon ammodendron is a succulent xerohalophyte species that exhibits strong resistance to abiotic stress. In this study, we isolated HaASR2 from H. ammodendron and demonstrated its detailed molecular function for drought and salt stress tolerance. HaASR2 interacted with the HaNHX1 protein, and its expression was significantly up-regulated under osmotic stress. Overexpression of HaASR2 improved drought and salt tolerance by enhancing water use efficiency and photosynthetic capacity in Arabidopsis thaliana. Overexpression of HaASR2 maintained the homeostasis of reactive oxygen species (ROS) and decreased sensitivity to exogenous ABA and endogenous ABA levels by down-regulating ABA biosynthesis genes under drought stress. Furthermore, a transcriptomic comparison between wild-type and HaASR2 transgenic Arabidopsis plants indicated that HaASR2 significantly induced the expression of 896 genes in roots and 406 genes in shoots under osmotic stress. Gene ontology (GO) enrichment analysis showed that those DEGs were mainly involved in ROS scavenging, metal ion homeostasis, response to hormone stimulus, etc. The results demonstrated that HaASR2 from the desert shrub, H. ammodendron, plays a critical role in plant adaptation to drought and salt stress and could be a promising gene for the genetic improvement of crop abiotic stress tolerance.

Drought stress tolerance mechanisms and their potential common indicators to salinity, insights from the wild watermelon (Citrullus lanatus): A review

Climate change has escalated the effect of drought on crop production as it has negatively altered the environmental condition. Wild watermelon grows abundantly in the Kgalagadi desert even though the environment is characterized by minimal rainfall, high temperatures and intense sunshine during growing season. This area is also characterized by sandy soils with low water holding capacity, thus bringing about drought stress. Drought stress affects crop productivity through its effects on development and physiological functions as dictated by molecular responses. Not only one or two physiological process or genes are responsible for drought tolerance, but a combination of various factors do work together to aid crop tolerance mechanism. Various studies have shown that wild watermelon possess superior qualities that aid its survival in unfavorable conditions. These mechanisms include resilient root growth, timely stomatal closure, chlorophyll fluorescence quenching under water deficit as key physiological responses. At biochemical and molecular level, the crop responds through citrulline accumulation and expression of genes associated with drought tolerance in this species and other plants. Previous salinity stress studies involving other plants have identified citrulline accumulation and expression of some of these genes (chloroplast APX, Type-2 metallothionein), to be associated with tolerance. Emerging evidence indicates that the upstream of functional genes are the transcription factor that regulates drought and salinity stress responses as well as adaptation. In this review we discuss the drought tolerance mechanisms in watermelons and some of its common indicators to salinity at physiological, biochemical and molecular level.

The battle of crops against drought: Genetic dissection and improvement

With ongoing global climate change, water scarcity-induced drought stress remains a major threat to agricultural productivity. Plants undergo a series of physiological and morphological changes to cope with drought stress, including stomatal closure to reduce transpiration and changes in root architecture to optimize water uptake. Combined phenotypic and multi-omics studies have recently identified a number of drought-related genetic resources in different crop species. The functional dissection of these genes using molecular techniques has enriched our understanding of drought responses in crops and has provided genetic targets for enhancing resistance to drought. Here, we review recent advances in the cloning and functional analysis of drought resistance genes and the development of technologies to mitigate the threat of drought to crop production.

AtTLP2, a Tubby-like protein, plays intricate roles in abiotic stress signalling

The Arabidopsis Tubby-like protein (TLP) encoding gene, AtTLP2, plays intricate roles during ABA-dependent abiotic stress signalling, particularly salt and dehydration stress responses. TLPs (Tubby-like proteins) are a small group of eukaryotic proteins characterized by the presence of a Tubby domain. The plant TLPs have been widely shown to play important roles during abiotic stress signaling. In this study, we investigated the role of an Arabidopsis TLP, AtTLP2, in mediating abiotic stress responses. Both attlp2 null mutant and overexpression (OE) lines, in Arabidopsis, were studied which indicated the role of the gene also in development. The attlp2 mutant showed an overall dwarfism, while its overexpression caused enhanced growth. AtTLP2 localized to the plasma membrane (PM) and showed nuclear translocation in response to dehydration stress. The protein interacted with ASK1 and ASK2, but failed to show transactivation activity in yeast. AtTLP2 was transcriptionally induced by stress, caused by salt, dehydration and ABA. The attlp2 mutant was insensitive to ABA, but hypersensitive to oxidative stress at all stages of growth. ABA insensitivity conferred tolerance to salt and osmotic stresses at the germination and early seedling growth stages, but caused hypersensitivity to salt and drought stresses at advanced stages of growth. The OE lines were more sensitive to ABA, causing increased sensitivity to most stresses at the seed germination stage, but conferring tolerance to salt and osmotic stresses at more advanced stages of development. The stomata of the attlp2 mutant were less responsive to ABA and H₂O_2, while that of the OE lines exhibited greater sensitivity. Several ABA-regulated stress responsive marker genes were found to be downregulated in the mutant, but upregulated in the OE lines. The study establishes that AtTLP2 plays intricate roles in abiotic stress signaling, and the response may be largely ABA dependent.

Transcriptomic and metabolic regulatory network characterization of drought responses in tobacco

Drought stress usually causes huge economic losses for tobacco industries. Drought stress exhibits multifaceted impacts on tobacco systems through inducing changes at different levels, such as physiological and chemical changes, changes of gene transcription and metabolic changes. Understanding how plants respond and adapt to drought stress helps generate engineered plants with enhanced drought resistance. In this study, we conducted multiple time point-related physiological, biochemical,transcriptomic and metabolic assays using K326 and its derived mutant 28 (M28) with contrasting drought tolerance. Through integrative analyses of transcriptome and metabolome,we observed dramatic changes of gene expression and metabolic profiles between M28 and K326 before and after drought treatment. we found that some of DEGs function as key enzymes responsible for ABA biosynthesis and metabolic pathway, thereby mitigating impairment of drought stress through ABA signaling dependent pathways. Four DEGs were involved in nitrogen metabolism, leading to synthesis of glutamate (Glu) starting from NO-3 /NO-2 that serves as an indicator for stress responses. Importantly, through regulatory network analyses, we detected several drought induced TFs that regulate expression of genes responsible for ABA biosynthesis through network, indicating direct and indirect involvement of TFs in drought responses in tobacco. Thus, our study sheds some mechanistic insights into how plant responding to drought stress through transcriptomic and metabolic changes in tobacco. It also provides some key TF or non-TF gene candidates for engineering manipulation for breeding new tobacco varieties with enhanced drought tolerance.

TaERF87 and TaAKS1 synergistically regulate TaP5CS1/TaP5CR1-mediated proline biosynthesis to enhance drought tolerance in wheat

Drought stress limits wheat production and threatens food security world-wide. While ethylene-responsive factors (ERFs) are known to regulate plant response to drought stress, the regulatory mechanisms responsible for a tolerant phenotype remain unclear. Here, we describe the positive regulatory role of TaERF87 in mediating wheat tolerance to drought stress. TaERF87 overexpression (OE) enhances drought tolerance, while silencing leads to drought sensitivity in wheat. RNA sequencing with biochemical assays revealed that TaERF87 activates the expression of the proline biosynthesis genes TaP5CS1 and TaP5CR1 via direct binding to GCC-box elements. Furthermore, proline accumulates to higher levels in TaERF87- and TaP5CS1-OE lines than that in wild-type plants under well-watered and drought stress conditions concomitantly with enhanced drought tolerance in these transgenic lines. Moreover, the interaction between TaERF87 and the bHLH transcription factor TaAKS1 synergistically enhances TaP5CS1 and TaP5CR1 transcriptional activation. TaAKS1 OE also increases wheat drought tolerance by promoting proline accumulation. Additionally, our findings verified that TaERF87 and TaAKS1 are targets of abscisic acid-responsive element binding factor 2 (TaABF2). Together, our study elucidates the mechanisms underlying a positive response to drought stress mediated by the TaABF2-TaERF87/TaAKS1-TaP5CS1/TaP5CR1 module, and identifies candidate genes for the development of elite drought-tolerant wheat varieties.

Conserved hierarchical gene regulatory networks for drought and cold stress response in Myrica rubra

Stress response in plant is regulated by a large number of genes co-operating in diverse networks that serve multiple adaptive process. To understand how gene regulatory networks (GRNs) modulating abiotic stress responses, we compare the GRNs underlying drought and cold stresses using samples collected at 4 or 6 h intervals within 48 h in Chinese bayberry (Myrica rubra). We detected 7,583 and 8,840 differentially expressed genes (DEGs) under drought and cold stress respectively, which might be responsive to environmental stresses. Drought- and cold-responsive GRNs, which have been built according to the timing of transcription under both abiotic stresses, have a conserved trans-regulator and a common regulatory network. In both GRNs, basic helix-loop-helix family transcription factor (bHLH) serve as central nodes. MrbHLHp10 transcripts exhibited continuous increase in the two abiotic stresses and acts upstream regulator of ASCORBATE PEROXIDASE (APX) gene. To examine the potential biological functions of MrbHLH10, we generated a transgenic Arabidopsis plant that constitutively overexpresses the MrbHLH10 gene. Compared to wild-type (WT) plants, overexpressing transgenic Arabidopsis plants maintained higher APX activity and biomass accumulation under drought and cold stress. Consistently, RNAi plants had elevated susceptibility to both stresses. Taken together, these results suggested that MrbHLH10 mitigates abiotic stresses through the modulation of ROS scavenging.

ThASR3 confers salt and osmotic stress tolerances in transgenic Tamarix and Arabidopsis

BACKGROUND

ASR (abscisic acid-, stress-, and ripening-induced) gene family plays a crucial role in responding to abiotic stresses in plants. However, the roles of ASR genes protecting plants against high salt and drought stresses remain unknown in Tamarix hispida.

RESULTS

In this study, a salt and drought-induced ASR gene, ThASR3, was isolated from Tamarix hispida. Transgenic Arabidopsis overexpressing ThASR3 exhibited stimulating root growth and increasing fresh weight compared with wild-type (WT) plants under both salt and water deficit stresses. To further analyze the gain- and loss-of-function of ThASR3, the transgenic T. hispida plants overexpressing or RNA interference (RNAi)-silencing ThASR3 were generated using transient transformation. The overexpression of ThASR3 in Tamarix and Arabidopsis plants displayed enhanced reactive oxygen species (ROS) scavenging capability under high salt and osmotic stress conditions, including increasing the activities of antioxidant enzymes and the contents of proline and betaine, and reducing malondialdehyde (MDA) content and electrolyte leakage rates.

CONCLUSION

Our results indicate that ThASR3 functions as a positive regulator in Tamarix responses to salt and osmotic stresses and confers multiple abiotic stress tolerances in transgenic plants, which may have an important application value in the genetic improvement of forest tree resistance.

Amino acid motifs for the identification of novel protein interactants

Biological systems consist of multiple components of different physical and chemical properties that require complex and dynamic regulatory loops to function efficiently. The discovery of ever more novel interacting sites in complex proteins suggests that we are only beginning to understand how cellular and biological functions are integrated and tuned at the molecular and systems levels. Here we review recently discovered interacting sites which have been identified through rationally designed amino acid motifs diagnostic for specific molecular functions, including enzymatic activities and ligand-binding properties. We specifically discuss the nature of the latter using as examples, novel hormone recognition and gas sensing sites that occur in moonlighting protein complexes. Drawing evidence from the current literature, we discuss the potential implications at the cellular, tissue, and/or organismal levels of such non-catalytic interacting sites and provide several promising avenues for the expansion of amino acid motif searches to discover hitherto unknown protein interactants and interaction networks. We believe this knowledge will unearth unexpected functions in both new and well-characterized proteins, thus filling existing conceptual gaps or opening new avenues for applications either as drug targets or tools in pharmacology, cell biology and bio-catalysis. Beyond this, motif searches may also support the design of novel, effective and sustainable approaches to crop improvements and the development of new therapeutics.

Rhizosheath: An adaptive root trait to improve plant tolerance to phosphorus and water deficits?

Drought and nutrient limitations adversely affect crop yields, with below-ground traits enhancing crop production in these resource-poor environments. This review explores the interacting biological, chemical and physical factors that determine rhizosheath (soil adhering to the root system) development, and its influence on plant water uptake and phosphorus acquisition in dry soils. Identification of quantitative trait loci for rhizosheath development indicate it is genetically determined, but the microbial community also directly (polysaccharide exudation) and indirectly (altered root hair development) affect its extent. Plants with longer and denser root hairs had greater rhizosheath development and increased P uptake efficiency. Moreover, enhanced rhizosheath formation maintains contact at the root-soil interface thereby assisting water uptake from drying soil, consequently improving plant survival in droughted environments. Nevertheless, it can be difficult to determine if rhizosheath development is a cause or consequence of improved plant adaptation to dry and nutrient-depleted soils. Does rhizosheath development directly enhance plant water and phosphorus use, or do other tolerance mechanisms allow plants to invest more resources in rhizosheath development? Much more work is required on the interacting genetic, physical, biochemical and microbial mechanisms that determine rhizosheath development, to demonstrate that selection for rhizosheath development is a viable crop improvement strategy.

Regulation of Drought and Salt Tolerance by OsSKL2 and OsASR1 in Rice

Abiotic stresses such as salinity and drought greatly impact the growth and production of crops worldwide. Here, a shikimate kinase-like 2 (SKL2) gene was cloned from rice and characterized for its regulatory function in salinity and drought tolerance. OsSKL2 was localized in the chloroplast, and its transcripts were significantly induced by drought and salinity stress as well as H₂O₂ and abscisic acid (ABA) treatment. Meanwhile, overexpression of OsSKL2 in rice increased tolerance to salinity, drought and oxidative stress by increasing antioxidant enzyme activity, and reducing levels of H₂O₂, malondialdehyde, and relative electrolyte leakage. In contrast, RNAi-induced suppression of OsSKL2 increased sensitivity to stress treatment. Interestingly, overexpression of OsSKL2 also increased sensitivity to exogenous ABA, with an increase in reactive oxygen species (ROS) accumulation. Moreover, OsSKL2 was found to physically interact with OsASR1, a well-known chaperone-like protein, which also exhibited positive roles in salt and drought tolerance. A reduction in ROS production was also observed in leaves of Nicotiana benthamiana showing transient co-expression of OsSKL2 with OsASR1. Taken together, these findings suggest that OsSKL2 together with OsASR1 act as important regulatory factors that confer salt and drought tolerance in rice via ROS scavenging.

OsASR6 Enhances Salt Stress Tolerance in Rice

High salinity seriously affects crop growth and yield. Abscisic acid-, stress-, and ripening-induced (ASR) proteins play an important role in plant responses to multiple abiotic stresses. In this study, we identified a new salt-induced ASR gene in rice (OsASR6) and functionally characterized its role in mediating salt tolerance. Transcript levels of OsASR6 were upregulated under salinity stress, H₂O₂ and abscisic acid (ABA) treatments. Nuclear and cytoplasmic localization of the OsASR6 protein were confirmed. Meanwhile, a transactivation activity assay in yeast demonstrated no self-activation ability. Furthermore, transgenic rice plants overexpressing OsASR6 showed enhanced salt and oxidative stress tolerance as a result of reductions in H₂O₂, malondialdehyde (MDA), Na/K and relative electrolyte leakage. In contrast, OsASR6 RNAi transgenic lines showed opposite results. A higher ABA content was also measured in the OsASR6 overexpressing lines compared with the control. Moreover, OsNCED1, a key enzyme of ABA biosynthesis, was found to interact with OsASR6. Collectively, these results suggest that OsASR6 serves primarily as a functional protein, enhancing tolerance to salt stress, representing a candidate gene for genetic manipulation of new salinity-resistant lines in rice.

Transcriptome Analysis of Moso Bamboo (Phyllostachys edulis) Reveals Candidate Genes Involved in Response to Dehydration and Cold Stresses

Bamboo (Bambusoideae) belongs to the grass family (Poaceae) and has been utilized as one of the most important nontimber forest resources in the world. Moso bamboo (Phyllostachys edulis) is a large woody bamboo with high ecological and economic values. Global climate change brings potential challenges to the normal growth of moso bamboo, and hence its production. Despite the release of moso bamboo genome sequence, the knowledge on genome-wide responses to abiotic stress is still limited. In this study, we generated a transcriptome data set with respect to dehydration and cold responses of moso bamboo using RNA-seq technology. The differentially expressed genes (DEGs) under treatments of dehydration and cold stresses were identified. By combining comprehensive gene ontology (GO) analysis, time-series analysis, and co-expression analysis, candidate genes involved in dehydration and cold responses were identified, which encode abscisic acid (ABA)/water deficit stress (WDS)-induced protein, late embryogenesis abundant (LEA) protein, 9-cis-epoxycarotenoid dioxygenase (NCED), anti-oxidation enzymes, transcription factors, etc. Additionally, we used PeLEA14, a dehydration-induced gene encoding an "atypical" LEA protein, as an example to validate the function of the identified stress-related gene in tolerance to abiotic stresses, such as drought and salt. In this study, we provided a valuable genomic resource for future excavation of key genes involved in abiotic stress responses and genetic improvement of moso bamboo to meet the requirement for environmental resilience and sustainable production.

Insights into the Regulation of Rice Seed Storability by Seed Tissue-Specific Transcriptomic and Metabolic Profiling

Non-dormant seeds are continuously aging and deteriorating during storage, leading to declining seed vigor, which is a challenge for the rice seed industry. Improving the storability of seeds is of great significance to ensure the quality of rice and national food security. Through a set of chromosome segment substitution lines population constructed using japonica rice NIP as donor parent and indica rice ZS97 as recurrent parent, we performed seed storability QTL analysis and selected four non-storable NILs to further investigate the storability regulatory mechanisms underlying it. The seeds were divided into four tissues, which were the embryo, endosperm, aleurone layer, and hull, and tissue-specific transcriptome and metabolome analyses were performed on them. By exploring the common differentially expressed genes and differentially accumulated metabolites, as well as the KEGG pathway of the four non-storable NILs, we revealed that the phenylpropanoid biosynthesis pathway and diterpenoid biosynthesis pathway played a central role in regulating seed storability. Integrated analysis pinpointed 12 candidate genes that may take part in seed storability. The comprehensive analysis disclosed the divergent and synergistic effect of different seed tissues in the regulation of rice storability.

OsASR6 Alleviates Rice Resistance to Xanthomonas oryzae via Transcriptional Suppression of OsCIPK15

The plant-specific ASR (abscisic acid, stress and ripening) transcription factors are pivotal regulators of plant responses to abiotic stresses. However, their functions in plant disease resistance remain largely unknown. In this study, we revealed the role of OsASR6 in rice plants’ resistance to two important bacterial diseases caused by Xanthomonas oryzae pv. oryzae (Xoo) and X. oryzae pv. oryzicola (Xoc) and elucidated the mechanisms underlying OsASR6-regulated resistance. The expression of OsASR6 was strongly elevated in response to both Xoo and Xoc challenges. Silencing of OsASR6 in OsASR6-RNAi transgenic plants markedly enhanced rice resistance to the two bacterial pathogens. Moreover, comparative transcriptome analyses for OsASR6-RNAi and wild-type plants inoculated and uninoculated with Xoc demonstrated that OsASR6 suppressed rice resistance to Xoc by comprehensively fine-tuning CIPK15- and WRKY45-1-mediated immunity, SA signaling and redox homeostasis. Further luciferase reporter assays confirmed that OsASR6 negatively regulated CIPK15 but not WRKY45-1 expression in planta. Overexpression of OsCIPK15 strongly enhanced rice resistance to Xoo and Xoc. Collectively, these results reveal that OsASR6 alleviates rice resistance through the transcriptional suppression of OsCIPK15, and thus links calcium signaling to rice resistance against X. oryzae. Our findings provide insight into the mechanisms underlying OsASR6-mediated regulation of rice resistance to X. oryzae.

ZmLBD5 Increases Drought Sensitivity by Suppressing ROS Accumulation in Arabidopsis

Drought stress is known to significantly limit crop growth and productivity. Lateral organ boundary domain (LBD) transcription factors-particularly class-I members-play essential roles in plant development and biotic stress. However, little information is available on class-II LBD genes related to abiotic stress in maize. Here, we cloned a maize class-II LBD transcription factor, ZmLBD5, and identified its function in drought stress. Transient expression, transactivation, and dimerization assays demonstrated that ZmLBD5 was localized in the nucleus, without transactivation, and could form a homodimer or heterodimer. Promoter analysis demonstrated that multiple drought-stress-related and ABA response cis-acting elements are present in the promoter region of ZmLBD5. Overexpression of ZmLBD5 in Arabidopsis promotes plant growth under normal conditions, and suppresses drought tolerance under drought conditions. Furthermore, the overexpression of ZmLBD5 increased the water loss rate, stomatal number, and stomatal apertures. DAB and NBT staining demonstrated that the reactive oxygen species (ROS) decreased in ZmLBD5-overexpressed Arabidopsis. A physiological index assay also revealed that SOD and POD activities in ZmLBD5-overexpressed Arabidopsis were higher than those in wild-type Arabidopsis. These results revealed the role of ZmLBD5 in drought stress by regulating ROS levels.

TaNBR1, a Novel Wheat NBR1-like Domain Gene Negatively Regulates Drought Stress Tolerance in Transgenic Arabidopsis

Drought stress is an important factor that severely affects crop yield and quality. Autophagy has a crucial role in the responses to abiotic stresses. In this study, we explore TaNBR1 in response to drought stress. Expression of the TaNBR1 gene was strongly induced by NaCl, PEG, and abscisic acid treatments. The TaNBR1 protein is localized in the Golgi apparatus and autophagosome. Transgenic Arabidopsis plants overexpressing TaNBR1 exhibited reduced drought tolerance. When subjected to drought stress, compared to the wild-type (WT) lines, the transgenic overexpressing TaNBR1 plants had a lower seed germination rate, relative water content, proline content, and reduced accumulation of antioxidant enzymes, i.e., superoxide dismutase, peroxidase, and catalase, as well as higher chlorophyll losses, malondialdehyde contents, and water loss. The transgenic plants overexpressing TaNBR1 produced much shorter roots in response to mannitol stress, in comparison to the WT plants, and they exhibited greater sensitivity to abscisic acid treatment. The expression levels of the genes related to stress in the transgenic plants were affected in response to drought stress. Our results indicate that TaNBR1 negatively regulates drought stress responses by affecting the expression of stress-related genes in Arabidopsis.

Inactivating transcription factor OsWRKY5 enhances drought tolerance through abscisic acid signaling pathways

During crop cultivation, water-deficit conditions retard growth, thus reducing crop productivity. Therefore, uncovering the mechanisms behind drought tolerance is a critical task for crop improvement. Here, we show that the rice (Oryza sativa) WRKY transcription factor OsWRKY5 negatively regulates drought tolerance. We determined that OsWRKY5 was mainly expressed in developing leaves at the seedling and heading stages, and that its expression was reduced by drought stress and by treatment with NaCl, mannitol, and abscisic acid (ABA). Notably, the genome-edited loss-of-function alleles oswrky5-2 and oswrky5-3 conferred enhanced drought tolerance, measured as plant growth under water-deficit conditions. Conversely, the overexpression of OsWRKY5 in the activation-tagged line oswrky5-D resulted in higher susceptibility under the same conditions. The loss of OsWRKY5 activity increased sensitivity to ABA, thus promoting ABA-dependent stomatal closure. Transcriptome deep sequencing and reverse transcription quantitative polymerase chain reaction analyses demonstrated that the expression of abiotic stress-related genes including rice MYB2 (OsMYB2) was upregulated in oswrky5 knockout mutants and downregulated in oswrky5-D mutants. Moreover, dual-luciferase, yeast one-hybrid, and chromatin immunoprecipitation assays showed that OsWRKY5 directly binds to the W-box sequences in the promoter region of OsMYB2 and represses OsMYB2 expression, thus downregulating genes downstream of OsMYB2 in the ABA signaling pathways. Our results demonstrate that OsWRKY5 functions as a negative regulator of ABA-induced drought stress tolerance, strongly suggesting that inactivation of OsWRKY5 or manipulation of key OsWRKY5 targets could be useful to improve drought tolerance in rice cultivars.

Integration of transcriptomic and proteomic analyses reveals several levels of metabolic regulation in the excess starch and early senescent leaf mutant lses1 in rice

BACKGROUND

The normal metabolism of transitory starch in leaves plays an important role in ensuring photosynthesis, delaying senescence and maintaining high yield in crops. OsCKI1 (casein kinase I1) plays crucial regulatory roles in multiple important physiological processes, including root development, hormonal signaling and low temperature-treatment adaptive growth in rice; however, its potential role in regulating temporary starch metabolism or premature leaf senescence remains unclear. To reveal the molecular regulatory mechanism of OsCKI1 in rice leaves, physiological, transcriptomic and proteomic analyses of leaves of osckI1 allele mutant lses1 (leaf starch excess and senescence 1) and its wild-type varieties (WT) were performed.

RESULTS

Phenotypic identification and physiological measurements showed that the lses1 mutant exhibited starch excess in the leaves and an obvious leaf tip withering phenotype as well as high ROS and MDA contents, low chlorophyll content and protective enzyme activities compared to WT. The correlation analyses between protein and mRNA abundance are weak or limited. However, the changes of several important genes related to carbohydrate metabolism and apoptosis at the mRNA and protein levels were consistent. The protein-protein interaction (PPI) network might play accessory roles in promoting premature senescence of lses1 leaves. Comprehensive transcriptomic and proteomic analysis indicated that multiple key genes/proteins related to starch and sugar metabolism, apoptosis and ABA signaling exhibited significant differential expression. Abnormal increase in temporary starch was highly correlated with the expression of starch biosynthesis-related genes, which might be the main factor that causes premature leaf senescence and changes in multiple metabolic levels in leaves of lses1. In addition, four proteins associated with ABA accumulation and signaling, and three CKI potential target proteins related to starch biosynthesis were up-regulated in the lses1 mutant, suggesting that LSES1 may affect temporary starch accumulation and premature leaf senescence through phosphorylation crosstalk ABA signaling and starch anabolic pathways.

CONCLUSION

The current study established the high correlation between the changes in physiological characteristics and mRNA and protein expression profiles in lses1 leaves, and emphasized the positive effect of excessive starch on accelerating premature leaf senescence. The expression patterns of genes/proteins related to starch biosynthesis and ABA signaling were analyzed via transcriptomes and proteomes, which provided a novel direction and research basis for the subsequent exploration of the regulation mechanism of temporary starch and apoptosis via LSES1/OsCKI1 in rice.

Integration of the Physiology, Transcriptome and Proteome Reveals the Molecular Mechanism of Drought Tolerance in Cupressus gigantea

Drought stress can dramatically impair woody plant growth and restrict the geographical distribution of many tree species. To better understand the dynamics between the response and mechanism of Cupressus gigantea to drought and post-drought recovery, a comparative analysis was performed, relying on physiological measurements, RNA sequencing (RNA-Seq) and two-dimensional gel electrophoresis (2-DE) proteins. In this study, the analyses revealed that photosynthesis was seriously inhibited, while osmolyte contents, antioxidant enzyme activity and non-enzymatic antioxidant contents were all increased under drought stress in seedlings. Re-watering led to a recovery in most of the parameters analyzed, mainly the photosynthetic parameters and osmolyte contents. Transcriptomic and proteomic profiling suggested that most of the differentially expressed genes (DEGs) and differentially expressed proteins (DEPs) were specifically altered, and a few were consistently altered. Drought induced a common reduction in the level of DEGs and DEPs associated with photosynthesis. Notably, DEGs and DEPs involved in reactive oxygen species (ROS) scavenging, such as ascorbate oxidase and superoxide dismutase (SOD), showed an inverse pattern under desiccation. This study may improve our understanding of the underlying molecular mechanisms of drought resistance in C. gigantea and paves the way for more detailed molecular analysis of the candidate genes.