Tetraspanin 5 orchestrates resilience to salt stress through the regulation of ion and reactive oxygen species homeostasis in rice.

Tetraspanins (TETs) are integral membrane proteins, characterized by four transmembrane domains and a unique signature motif in their large extracellular loop. They form dynamic supramolecular complexes called tetraspanin-enriched microdomains (TEMs), through interactions with partner proteins. In plants, TETs are involved in development, reproduction and immune responses, but their role in defining abiotic stress responses is largely underexplored. We focused on OsTET5, which is differentially expressed under various abiotic stresses and localizes to both plasma membrane and endoplasmic reticulum. Using overexpression and underexpression transgenic lines we demonstrate that OsTET5 contributes to salinity and drought stress tolerance in rice. OsTET5 can interact with itself in yeast, suggesting homomer formation. Immunoblotting of native PAGE of microsomal fraction enriched from OsTET5-Myc transgenic rice lines revealed multimeric complexes containing OsTET5, suggesting the potential formation of TEM complexes. Transcriptome analysis, coupled with quantitative PCR-based validation, of OsTET5-altered transgenic lines unveiled the differential expression patterns of several stress-responsive genes, as well as those coding for transporters under salt stress. Notably, OsTET5 plays a crucial role in maintaining the ionic equilibrium during salinity stress, particularly by preserving an elevated potassium-to-sodium (K+/Na+) ratio. OsTET5 also regulates reactive oxygen species homeostasis, primarily by modulating the gene expression and activities of antioxidant pathway enzymes and proline accumulation. Our comprehensive investigation underscores the multifaceted role of OsTET5 in rice, accentuating its significance in developmental processes and abiotic stress tolerance. These findings open new avenues for potential strategies aimed at enhancing stress resilience and making valuable contributions to global food security.

Caffeic acid O-methyltransferase from Ligusticum chuanxiong alleviates drought stress, and improves lignin and melatonin biosynthesis.

Drought stress is a major constraint on plant growth and agricultural productivity. Caffeic acid O-methyltransferase (COMT), an enzyme involved in the methylation of various substrates, plays a pivotal role in plant responses to abiotic stress. The involvement of COMTs in drought response, particularly through the enhancement of lignin and melatonin biosynthesis, remains poorly understood. In this study, LcCOMT was firstly proposed to be associated with the biosynthesis of both lignin and melatonin, as demonstrated through sequence comparison, phylogenetic analysis, and conserved motif identification. In vitro enzymatic assays revealed that LcCOMT effectively methylates N-acetylserotonin to melatonin, albeit with a higher Km value compared to caffeic acid. Site-directed mutagenesis of residues Phe171 and Asp269 resulted in a significant reduction in catalytic activity for caffeic acid, with minimal impact on N-acetylserotonin, underscoring the specificity of these residues in substrate binding and catalysis. Under drought conditions, LcCOMT expression was significantly upregulated. Overexpression of LcCOMT gene in Arabidopsis plants conferred enhanced drought tolerance, characterized by elevated lignin and melatonin levels, increased chlorophyll and carotenoid content, heightened activities of antioxidant enzymes peroxidase (POD), catalase (CAT), and superoxide dismutase (SOD), and reduced malondialdehyde (MDA) and hydrogen peroxide (H2O2) accumulation. This study is among the few to demonstrate that COMT-mediated drought tolerance is achieved through the simultaneous promotion of lignin and melatonin biosynthesis. LcCOMT represents the first functionally characterized COMT in Apiaceae family, and it holds potential as a target for genetic enhancement of drought tolerance in future crop improvement strategies.

Genome-wide Association Studies of Photosynthetic and Agronomic Traits in Cowpea Collection.

Exploring genomic regions linked with drought tolerance and photosynthesis in cowpea could accelerate breeding of climate-resilient cowpea varieties A Genome-wide association study (GWAS) was conducted to identify marker-trait associations for agronomic and photosynthetic traits measured under well-watered and water-stressed conditions. One hundred and twelve cowpea accessions from IITA were phenotyped for agronomic and photosynthetic traits across three locations in two years: Ibadan, Ikenne (2020 and 2021) and Kano (2021 and 2022). The accessions were genotyped using 19,000 DArT-Seq SNP markers from which 9,210 markers were utilized for GWAS analysis using BLINK and mixed linear model (MLM) in GAPIT. Results revealed significant accession × environment interactions for measured traits while ΦPSII, ΦNO and ΦNPQ had significant and consistent correlations with grain yield across conditions. GWAS identified five SNP markers having consistent associations with grain yield under well-watered and water-stressed conditions and three markers associated with ΦNPQ and ΦNO. Gene annotations revealed Vigun04g169000 and Vigun08g168900 genes linked with grain yield and highly expressed under water-stressed conditions have functional roles in regulating plant development and adaptive response to environmental stress. Vigun07g133400, Vigun07g132700 and Vigun07g258000 genes linked with ΦNPQ and ΦNO are involved in activities controlling photoprotection and stress-induced damage in plants. This study identified natural genetic variation in cowpea and correlations between photosynthetic traits and grain yield under real-field drought conditions. The identified SNP markers upon validation would be valuable in marker-assisted selection and useful for cowpea breeders to harness the role of photosynthesis in genetic enhancement of cowpea tolerance to drought.

The BpPP2C-BpMADS11-BpERF61 signaling confers drought tolerance in Betula platyphylla.

Plant MADS-box proteins are vital for abiotic stress tolerance, yet their mechanisms for responding to drought remain poorly understood. Here, we investigated the drought tolerance mechanism of a MADS-box protein (BpMADS11) from birch (Betula platyphylla) using immunoprecipitation, Western blotting, yeast two-hybrid, yeast one-hybrid, ChIP, RNA-seq, and dual-luciferase assays to explore post-translational modifications, protein interactions, and gene regulation. Birch plants overexpressing BpMADS11 exhibited enhanced drought tolerance, while knockout lines displayed reduced tolerance. Under drought conditions, BpMADS11 interacts with protein phosphatase 2C22 (BpPP2C22), which dephosphorylates BpMADS11. Birch plants that overexpress BpMADS11 and lack BpPP2C22 show significantly reduced drought tolerance compared with those that only overexpress BpMADS11. BpMADS11 regulates the expression of BpERF61 by binding to CArG-box in its promoter. The dephosphorylated BpMADS11 exhibits increased DNA binding ability and increased expression of BpERF61. Like BpMADS11, birch plants overexpressing BpERF61 show improved drought tolerance, while those with BpERF61 knockout exhibit decreased tolerance. BpERF61 binds to specific DNA motifs including 'CACGTG' (G-box), 'GGGCCCC', and 'TTGGAT' to regulate the genes related to drought stress. Collectively, BpMADS11 undergoes dephosphorylation through its interaction with BpPP2C22, prompting the expression of BpERF61. Subsequently, BpERF61 regulates downstream genes by binding to specific DNA motifs, thereby enhancing drought tolerance.

Unravelling the molecular mechanism underlying drought stress tolerance in Dinanath (Pennisetum pedicellatum Trin.) grass via integrated transcriptomic and metabolomic analyses.

Dinanath grass (Pennisetum pedicellatum Trin.) is an extensively grown forage grass known for its significant drought resilience. In order to comprehensively grasp the adaptive mechanism of Dinanath grass in response to water deficient conditions, transcriptomic and metabolomics were applied in the leaves of Dinanath grass exposed to two distinct drought intensities (48-hour and 96-hour). Transcriptomic analysis of Dinanath grass leaves revealed that a total of 218 and 704 genes were differentially expressed under 48- and 96-hour drought conditions, respectively. The genes that were expressed differently (DEGs) and the metabolites that accumulated in response to 48-hour drought stress mainly showed enrichment in the biosynthesis of secondary metabolites, particularly phenolics and flavonoids. Conversely, under 96-hour drought conditions, the enriched pathways predominantly involved lipid metabolism, specifically sterol lipids. In particular, phenylpropanoid pathway and brassinosteroid signaling played a crucial role in drought response to 48- and 96-hour water deficit conditions, respectively. This variation in drought response indicates that the adaptation mechanism in Dinanath grass is highly dependent on the intensity of drought stress. In addition, different genes associated with phenylpropanoid and fatty acid biosynthesis, as well as signal transduction pathways namely phenylalanine ammonia-lyase, putrescine hydroxycinnamoyl transferase, abscisic acid 8'-hydroxylase 2, syntaxin-61, lipoxygenase 5, calcium-dependent protein kinase and phospholipase D alpha one, positively regulated with drought tolerance. Combined transcriptomic and metabolomic analyses highlights the outstanding involvement of regulatory pathways related to secondary cell wall thickening and lignin biosynthesis in imparting drought tolerance to Dinanath grass leaves. These findings collectively contribute to an enhanced understanding of candidate genes and key metabolites relevant to drought response in Dinanath grass. Furthermore, they establish a groundwork for the creation of a transcriptome database aimed at developing abiotic stress-tolerant grasses and major crop varieties through both transgenic and genome editing approaches.

PagTPS1 and PagTPS10, the trehalose-6-phosphate synthase genes, increase trehalose content and enhance drought tolerance.

Trehalose-6-phosphate synthase (TPS) genes play an active role in the trehalose metabolism pathway that regulates the responses of plants to diverse stresses. However, the functional identification, comparison, and conservatism of TPS genes in the responses of woody plants, especially poplars, to drought stress remain unclear. Here, the trehalose content of 84K (Populus alba × P. glandulosa) poplars was down-regulated and PagTPS and PagTPP genes had diverse response patterns under drought stress. Physicochemical properties, expression patterns, and functions of PagTPS1 and PagTPS10, two class I members of TPS gene family, were identified and compared. Transgenic 84K poplars overexpressing PagTPS1 and PagTPS10 had significantly higher trehalose content with approximately 138% and 123%, respectively, and stronger drought tolerance compared to WT. PagTPS1 and PagTPS10 promoted the expression of TPPA genes and drought-responsive genes. Accordingly, poplars inhibiting PagTPS1 and PagTPS10 expression via RNA interference had lower trehalose content and drought tolerance. Simultaneously, overexpressing PagTPS1 and PagTPS10 improved the trehalose content and drought tolerance of Arabidopsis. Overall, we proposed a model of the effects of PagTPS1 and PagTPS10 as conservative regulators on the responses of plants to drought, which would provide new insights into the functional explorations of TPS genes in plants.

Natural GmACO1 allelic variations confer drought tolerance and influence nodule formation in soybean.

Soybean [Glycine max (L.) Merr.] is one of the most important, but a drought-sensitive, crops. Identifying the genes controlling drought tolerance is important in soybean breeding. Here, through a genome-wide association study, we identified one significant association locus, located on chromosome 8, which conferred drought tolerance variations in a natural soybean population. Allelic analysis and genetic validation demonstrated that GmACO1, encoding for a 1-aminocyclopropane-1-carboxylate oxidase, was the causal gene in this association locus, and positively regulated drought tolerance in soybean. Meanwhile, we determined that GmACO1 expression was reduced after rhizobial infection, and that GmACO1 negatively regulated soybean nodule formation. Overall, our findings provide insights into soybean cultivars for future breeding. Supplementary Information: The online version contains supplementary material available at 10.1007/s42994-024-00160-w.

Using seasonal physiological and biochemical responses to select forest components adapted to soybean and corn intercropping.

Given the increasing utilization of forest components in integration systems worldwide, coupled with the growing demand for food in regions facing water restrictions, this study aims to evaluate how physiological and biochemical parameters contribute to the diversification of adaptive mechanisms among native species and eucalyptus genotypes intercropped with soybean or corn. The native tree species Anadenanthera macrocarpa and Dipteryx alata, and the eucalyptus genotypes Urograndis I-144 and Urocam VM01, were grown in soybean and corn intercropping areas and evaluated in fall, winter, spring, and summer. The study evaluated morning water potential, chloroplast pigment concentration, gas exchange, cell damage, and antioxidant enzyme activity. Intercropped with soybean, development the of A. macrocarpa improved through instantaneous water use efficiency, energy use by the electron transport chain, chloroplast pigments, and catalase enzyme activity. On the other hand, A. macrocarpa when, intercropped with corn, despite increasing energy absorption by the reaction center, there is a need for non-photochemical dissipation and in the activity of the enzymes superoxide dismutase and ascorbate peroxidase in response to water and oxidative deficits. In D. alata, the physiological and biochemical responses were not influenced by intercropping but by seasons, with increased chloroplast pigments in fall and electron transport in summer. However, in corn intercropping, the dissipation of excess energy allowed leaf acclimatization. The I-144 and VM01 genotypes also showed no significant differences between intercrops. The results describe photosynthetic and biochemical challenges in the native species A. macrocarpa intercropped with corn, such as a greater need for enzymatic and non-enzymatic defense mechanisms in response to more negative water potential. In D. alata, the challenges are present in both intercrops due to improved mechanisms to protect the photosynthetic apparatus. The survival of the I-144 genotype may be inefficient in both intercrops under prolonged drought conditions, as it modifies the photosystem; in contrast, genotype VM01 was the most adapted to the system for using captured energy, reducing water loss and being resilient.

Leaf starch degradation by ß-amylase ZmBAM8 influences drought tolerance in maize.

As a typical C4 plant and important crop worldwide, maize is susceptible to drought. In maize, transitory starch (TS) turnover occurs in the vascular bundle sheath of leaves, differing from that in Arabidopsis (a C3 plant). This process, particularly its role in drought tolerance and the key starch-hydrolyzing enzymes involved, is not fully understood. We discovered that the expression of the ß-amylase (BAM) gene ZmBAM8 is highly upregulated in the drought-tolerant inbred line Chang7-2t. Inspired by this finding, we systematically investigated TS degradation in maize lines, including Chang7-2t, Chang7-2, B104, and ZmBAM8 overexpression (OE) and knockout (KO) lines. We found that ZmBAM8 was significantly induced in the vascular bundle sheath by drought, osmotic stress, and abscisic acid. The stress-induced gene expression and chloroplast localization of ZmBAM8 align with the tissue and subcellular sites where TS turnover occurs. The recombinant ZmBAM8 was capable of effectively hydrolyzing leaf starch. Under drought conditions, the leaf starch in ZmBAM8-OE plants substantially decreased under light, while that in ZmBAM8-KO plants did not decrease. Compared with ZmBAM8-KO plants, ZmBAM8-OE plants exhibited increased drought tolerance. Our study provides insights into the significance of leaf starch degradation in C4 crops and contributes to the development of drought-resistant maize.

CRISPR/dCas13(Rx) Derived RNA N6-methyladenosine (m6A) Dynamic Modification in Plant.

N6-methyladenosine (m6A) is the most prevalent internal modification of mRNA and plays an important role in regulating plant growth. However, there is still a lack of effective tools to precisely modify m6A sites of individual transcripts in plants. Here, programmable m6A editing tools are developed by combining CRISPR/dCas13(Rx) with the methyltransferase GhMTA (Targeted RNA Methylation Editor, TME) or the demethyltransferase GhALKBH10 (Targeted RNA Demethylation Editor, TDE). These editors enable efficient deposition or removal of m6A modifications at targeted sites of endo-transcripts GhECA1 and GhDi19 within a broad editing window ranging from 0 to 46 nt. TDE editor significantly decreases m6A levels by 24%-76%, while the TME editor increases m6A enrichment, ranging from 1.37- to 2.51-fold. Furthermore, installation and removal of m6A modifications play opposing roles in regulating GhECA1 and GhDi19 mRNA transcripts, which may be attributed to the fact that their m6A sites are located in different regions of the genes. Most importantly, targeting the GhDi19 transcript with TME editor plants results in a significant increase in root length and enhanced drought resistance. Collectively, these m6A editors can be applied to study the function of specific m6A modifications and have the potential for future applications in crop improvement.

The design and development of EcoBiomes: Multi-species synthetic microbial consortia inspired by natural desert microbiome to enhance the resilience of climate-sensitive ecosystems.

Synthetic microbial communities, which simplify the complexity of natural ecosystems while retaining their key features, are gaining momentum in engineering and biotechnology applications. One potential application is the development of bioinoculants, offering an eco-friendly, sustainable solution to promote plant growth and increase resilience to abiotic stresses amidst climate change. A potential source for stress-tolerant microbes is those associated with desert plants, evolved and shaped by selective pressures to promote host health under harsh environmental conditions. In our research, we aim to design and develop synthetic microbial consortia inspired by the natural microbiota of four desert plants native to the Arabian Peninsula, inferred from our previous work identifying the structure and predicting the function of these microbial communities using high throughput eDNA barcoding. To obtain culturable microbes that are manageable and traceable yet still representative of natural microbial communities, we combined multiple experimental protocols coupled with compatibility and synergy assessments, along with in planta testing. We isolated a total of 75 bacteria and conducted detailed biological evaluations, revealing that an overwhelming majority (84 %) of all isolates produced indole acetic acid (IAA), with 73 % capable of solubilizing phosphate, 60 % producing siderophores, 47 % forming biofilms, and 35 % producing ACC deaminase, all contributing to plant growth and stress tolerance. We constructed four synthetic microbial consortia, named EcoBiomes, consisting of synergistic combinations of multiple species that can co-exist without significant antagonism. Our preliminary data indicate that EcoBiomes enhance the resilience of heterologous host plants under simulated environmental stresses, including drought, heat, and salinity. EcoBiomes offer a unique, sustainable, and eco-friendly solution to mitigate the impact of climate change on sensitive ecosystems, ultimately affecting global food security.

Tissue-specific accumulation of PIP aquaporins of a particular heteromeric composition is part of the maize response to mycorrhiza and drought.

The systemic coordination of accumulation of plasma membrane aquaporins (PIP) was investigated in this study in relation to mycorrhized maize response to a rapid development of severe drought followed by rewatering. In non-mycorrhizal roots, drought led to a drop in PIP abundance, followed by a transient increase under rewatering, whereas leaves showed an opposite pattern. In contrast, mycorrhiza contributed to maintenance of high and stable levels of PIPs in both plant organs after an initial increase, prolonged over the irrigation period. Isoelectric focusing electrophoresis resolved up to 13 aquaporin complexes with highly reproducible pl positions across leaf and root samples, symbiotic and non-symbiotic, stressed or not. Mass spectrometry recognized in leaves and roots a different ratio of PIP1 and PIP2 subunits within 2D spots that accumulated the most. Regardless of symbiotic status, drought regulation of aquaporins in roots was manifested as the prevalence of complexes that comprise almost exclusively PIP2 monomers. In contrast, the leaf response involved enrichment in PIP1s. PIP1s are thought to enhance water transport, facilitate CO2 diffusion but also affect stomatal movements. These features, together with elevated aquaporin levels, might explain a stress tolerance mechanism observed in mycorrhizal plants, resulting in faster recovery of stomatal water conductance and CO2 assimilation rate after drought.

Involvement of the Metallothionein gene OsMT2b in Drought and Cadmium Ions Stress in Rice.

Abiotic stress is one of the major factors restricting the production of rice (Oryza sativa L.). Developing rice varieties with dual abiotic stress tolerance is essential to ensure sustained rice production, which is necessary to illustrate the regulation mechanisms underlying dual stress tolerance. At present, only a few genes that regulate dual abiotic stress tolerance have been reported. In this study, we determined that the expression of OsMT2b was induced by both drought and Cd2+ stress. After stress treatment, OsMT2b-overexpression lines exhibited enhanced drought tolerance and better physiological performance in terms of relative water content and electrolyte leakage compared with wild-type (WT). Further analysis indicated that ROS levels were lower in OsMT2b-overexpression lines than in WT following stress treatment, suggesting that OsMT2b-overexpression lines had a stronger ability to scavenge ROS under stress. Reverse transcription-quantitative PCR (RT-qPCR) results demonstrated that under drought stress, OsMT2b influenced the expression of genes involved in ROS scavenging to enhance drought tolerance in rice. In addition, OsMT2b-overexpression plants displayed increased tolerance to Cd2+ stress, and physiological assessment results were consistent with the observed phenotypic improvements. Thus, enhancing ROS scavenging ability through OsMT2b overexpression is a novel strategy to boost rice tolerance to both drought and Cd2+ stress, offering a promising approach for developing rice germplasm with enhanced resistance to the abiotic stressors.

Exogenous Substances Used to Relieve Plants from Drought Stress and Their Associated Underlying Mechanisms.

Drought stress (DS) is one of the abiotic stresses that plants encounter commonly in nature, which affects their life, reduces agricultural output, and prevents crops from growing in certain areas. To enhance plant tolerance against DS, abundant exogenous substances (ESs) have been attempted and proven to be effective in helping plants relieve DS. Understanding the effect of each ES on alleviation of plant DS and mechanisms involved in the DS relieving process has become a research focus and hotspot that has drawn much attention in the field of botany, agronomy, and ecology. With an extensive and comprehensive review and summary of hundred publications, this paper groups various ESs based on their individual effects on alleviating plant/crop DS with details of the underlying mechanisms involved in the DS-relieving process of: (1) synthesizing more osmotic adjustment substances; (2) improving antioxidant pathways; (3) promoting photosynthesis; (4) improving plant nutritional status; and (5) regulating phytohormones. Moreover, a detailed discussion and perspective are given in terms of how to meet the challenges imposed by erratic and severe droughts in the agrosystem through using promising and effective ESs in the right way and at the right time.

Early Growth and Physiological Acclimation to Shade and Water Restriction of Seven Sclerophyllous Species of the Mediterranean Forests of Central Chile.

The success of using active restoration in Mediterranean-type climate zones mostly depends on an appropriate matching of plant species and specific management prescriptions upon establishment. In this study, we assessed the early growth and short-term physiological acclimation of seven common species found in the sclerophyllous forests in central Chile to water restriction and shading. We established a nursery experiment that included three treatments (T0: sun-exposed and water-restricted, T1: sun-exposed and fully irrigated, and T2: shaded and fully irrigated) and seven tree species differing in their shade and drought tolerance (Quillaja saponaria Molina, Aristotelia chilensis (Mol.) Stuntz, Peumus boldus Molina, Lithraea caustica (Mol.) Hook. and Arn, Luma apiculata (DC.) Burret, Colliguaja odorifera Molina, and Escallonia pulverulenta (Ruiz and Prav.) Pers). We measured the increment in seedling height and different leaf morpho-physiological traits during two months in the dry season. Based on the measured traits, none of the species took advantage of the higher water availability in T1 relative to T0, but most of the species responded to the shade in T2, regardless of their shade or drought tolerance. Height increments due to shade varied from 0% in P. boldus to 203% in L. apiculata. Overall, all the species responded similarly to the treatments in specific leaf area, chlorophyll content index, photosynthetic rate, stomatal conductance, and intrinsic water use efficiency. This suggests that the species exhibited similar acclimation patterns of these parameters to shade and drought, even regarding the variation in midday xylem water potential found in the water-restricted treatment T0 (from -1.5 MPa in P. boldus to -3.1 MPa in E. pulverulenta). In this study, shading had a higher positive effect on the seedling performance of sclerophyllous species than watering, which at operational level highlights the need for investing in tree shelters when using these species in restoration programs.

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

Abscisic acid 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 a ubiquitin E3 ligase that participates in protein ubiquitination. PtrRZFP1 mainly functions in the nucleus and endoplasmic reticulum and is activated by drought and abscisic acid. 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 abscisic acid, PtrRZFP1 promoted the production of NO and H2O2 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 abscisic acid signaling, and mediated its ubiquitination and eventual degradation through the ubiquitination-26S proteasome system, indicating that PtrRZFP1 positively regulates the abscisic acid signaling pathway. Furthermore, the PtrPP2C-9-overexpression line was insensitive to abscisic acid 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.

Osmotolerant plant growth promoting bacteria mitigate adverse effects of drought stress on wheat growth.

Drought stress represents a major constraint with significant impacts on wheat crop globally. The use of plant growth-promoting bacteria (PGPB) has emerged as a promising strategy to alleviate the detrimental impacts of water stress and enhance plant development. We investigated 24 strains from diverse ecosystems, assessed for PGP traits and tolerance ability to abiotic stresses (drought, salinity, temperature, pH, heavy metals, pollutants, herbicides, and fungicides). The most effective bacterial strains Providencia vermicola ME1, Pantoea agglomerans Pa, Pseudomonas knackmussi MR6, and Bacillus sp D13 were chosen. Furthermore, these strains exhibited PGP activities under osmotic stress (0, 10, 20, and 30% PEG-6000). The impact of these osmotolerant PGPBs on wheat (Triticum durum L.) growth under drought stress was assessed at two plant growth stages. In an in vitro wheat seed germination experiment, bacterial inoculation significantly enhanced germination parameters. In pot experiments, the potential of these bacteria was evaluated in wheat plants under three treatments: Well-watered (100% field capacity), moderate stress (50% FC), and severe stress (25% FC). Results showed a significant decline in wheat growth parameters under increasing water stress for uninoculated seedlings. In contrast, bacterial inoculation mitigated these adverse effects, significantly improving morphological parameters and chlorophyll pigment contents under the stress conditions. While malondialdehyde (lipid peroxidation) and proline contents increased significantly with drought intensity, they decreased after bacterial inoculation. The antioxidant enzyme activities (GPX, CAT, and SOD) in plants decreased after bacterial inoculation. The increased root colonization capacity observed under water stress was attributed to their ability to favorable adaptations in a stressful environment. This study highlighted the potential of selected PGPB to alleviate water stress effects on wheat, promoting practical applications aimed at enhancing crop resilience under conditions of water shortage.

The Abscisic Acid Receptor Gene StPYL8-like from Solanum tuberosum Confers Tolerance to Drought Stress in Transgenic Plants.

Pyrabactin resistance 1-like (PYL) proteins are abscisic acid (ABA) receptors that play a crucial role in the plant's response to adverse environmental conditions. However, as of yet, there is limited research on the role of PYL proteins in potato. In this study, a potato PYL gene, StPYL8-like, was identified through transcriptome analysis under drought stress. Molecular characterization revealed that the StPYL8-like protein possesses a highly conserved PYL family domain. Evolutionary analysis demonstrated that StPYL8-like protein clusters with various PYL proteins are involved in stress responses across different species. Functional assays showed that StPYL8-like robustly responds to different abiotic stresses, including drought and ABA treatment. Furthermore, the transient and stable expressions of StPYL8-like in tobacco enhanced their drought resistance, leading to increased plant height, leaf number, and fresh weight, as well as an improved root system. Transgenic tobacco carrying the StPYL8-like gene exhibited lower malondialdehyde (MDA) levels and higher proline accumulation and antioxidant enzyme activity compared to wild-type plants under drought conditions. Moreover, StPYL8-like upregulated the expression of stress-responsive genes (NtRD29A, NtLEA5, NtP5CS, NtPOD, NtSOD, and NtCAT) in transgenic plants subjected to drought stress. Collectively, these findings highlight the positive regulatory role of the StPYL8-like gene in enhancing potato plants' response to drought stress.

Biochar coating promoted rice growth under drought stress through modulating photosynthetic apparatus, chloroplast ultrastructure, stomatal traits and ROS homeostasis.

Drought hampers agricultural production by constraining crop growth and development. Nevertheless, there has been limited exploration regarding the effect of biochar coating in enhancing seed germination under drought conditions and understanding its underlying mechanisms. To fill this gap and clarify the pathway to drought resistance, the current research investigated the protective effectiveness of BC on seedling establishment and subsequent growth of rice under drought conditions. Results showed that BC notably elevated emergence rate (5.5%), shoot length (27.4%), root length (33.4%), plant height (19.6/10.3%), leaf area (69.8/71.7%), and plant biomass (85.7/67.9%) after 15/30 days under drought conditions compared to the control. Biochar coating facilitated the maintenance of a stable chloroplast structure, reduced chlorophyll degradation, and sustained cell expansion. This contributed to the improvement of stomatal characteristics on both adaxial and abaxial leaf surfaces during drought stress, encompassing enhancements in stomatal density and aperture. The preservation of stomatal opening led to an increased photosynthetic capacity, thereby fostering elevated photosynthetic activity and heightened plant biomass under stressful conditions. Simultaneously, BC treatment significantly diminished the production of reactive oxygen species, preserved cell membrane integrity, and augmented the accumulation of osmotic protectants. These outcomes signify that biochar coating mitigates the deleterious impacts of drought stress on photosynthesis, stomatal aperture, chloroplast ultrastructure, osmotic regulation, and redox homeostasis in plants through specific water and nutrient regulation. Consequently, this enhances the tolerance and growth of rice under drought stress.

PeFUS3 Drives Lateral Root Growth Via Auxin and ABA Signalling Under Drought Stress in Populus.

Changes in root system architecture are vital for plant adaptation to drought stress, yet the underlying molecular mechanisms of this process remain largely elusive. Here, FUSCA3 (FUS3), a B3 domain transcription factor isolated from Populus euphratica, was found to be an important gene of regulating lateral root (LR) development under drought stress. The expression of PeFUS3 was strongly induced by ABA and dehydration treatments. Overexpressing PeFUS3 in poplar 84 K (P. alba × P. glandulosa) positively regulated LR growth and enhanced drought tolerance, while the knockout lines, generated by the CRISPR/Cas9 system, displayed repressed LR growth and weakened drought tolerance. Further investigation demonstrated that PeFUS3 activated the expression of PIN2, PIN6a and AUX1, which were key genes involved in auxin transport, suggesting PeFUS3 modulated LR development under drought stress through auxin signalling. Moreover, PeFUS3 directly upregulated PePYL3 expression, and overexpressing PePYL3 poplar lines exhibited significantly increased drought resistance. In addition, PeABF2, an ABA responsive transcription factor, interacted with PeFUS3 and activated its transcription, indicating PeFUS3 was involved in ABA signalling pathway. Taken together, PeFUS3 is a key regulator, maintaining root growth of poplar by modulating the crosstalk of auxin and ABA signalling under drought stress.