Plant Drought Research Articles

An Integrated Framework for Drought Stress in Plants.

With global warming, drought stress is becoming increasingly severe, causing serious impacts on crop yield and quality. In order to survive under adverse conditions such as drought stress, plants have evolved a certain mechanism to cope. The tolerance to drought stress is mainly improved through the synergistic effect of regulatory pathways, such as transcription factors, phytohormone, stomatal movement, osmotic substances, sRNA, and antioxidant systems. This study summarizes the research progress on plant drought resistance, in order to provide a reference for improving plant drought resistance and cultivating drought-resistant varieties through genetic engineering technology.

Mycorrhizal inoculation alters rhizosphere fungal community and root morphology to improve drought tolerance of resource-acquisitive but not resource-conservative Quercus species

The mutualistic association between mycorrhizal fungi and plants is well known to improve plant drought resistance. However, the influence of external inoculants on the interactions between soil microbial communities and plant functional traits and how these interactions improve plant drought tolerance under drought stress remain unclear. We conducted a pot inoculation experiment to assess the effect of two inoculated fungal strains (Clitopolius hobsonii NL-19 and C. sp. HSL-YX-7-A) on morphological traits and rhizosphere fungal communities of eight Quercus species seedlings. Plant and soil fungal traits were measured 2 months after inoculation and then underwent a short-term (33 days) drought rewetting treatment. The biomass of all tree species reduced significantly under drought stress followed by rewetting (drought treatment) compared with that in the control treatment (well-watered); however, inoculated mycorrhizal fungi (drought + mycorrhizal inoculation treatment) increased the biomass of five Quercus species (growth-promoting species (GPS) exhibiting a significant increase in biomass under mycorrhizal inoculation treatment than under the uninoculated treatment during drought stress, characterized by a resource-use acquisitive strategy) and had no effect on the other three Quercus species (non-growth-promoting species (NGPS) exhibiting no significant difference in biomass between mycorrhizal inoculation and uninoculated treatments during drought stress, characterized by a resource-use conservative strategy). The leaf traits of the two species groups (GPS and NGPS) varied little among the three treatments. The values of most root traits (e.g., specific root length and root length) of GPS increased significantly under drought and drought + mycorrhizal inoculation treatments compared with those in the control, whereas relatively minor variations were observed in NGPS among the three treatments. The fungal community composition and functional groups (primary trophic modes) in the drought treatment were altered for NGPS but not for GPS; additionally, they changed in the drought + mycorrhizal inoculation treatment for GPS but not for NGPS when compared with those in the drought treatment. Furthermore, the drought tolerance of GPS was improved directly by fungal functional groups (i.e., Pathotroph-Saprotroph- Symbiotrophs proliferation) and indirectly by root traits (e.g., increased specific root length), whereas NGPS may adapt to drought stress through other pathways (e.g., physiological and biochemical regulation). Overall, drought and mycorrhizal inoculation affected the root traits and fungal community structure of Quercus seedlings, which rely on plant resource-use strategies. Our results provide new insights into the relationship between plant resource-use strategies and soil microbes for improving plant performance under drought stress.

Drought Stress Effects and Ways for Improving Drought Tolerance in Impatiens walleriana Hook.f.—A Review

Drought is one of the main abiotic stresses affecting plant growth and development. Reduced plant yield and quality are primarily caused by the reductions in photosynthesis, mineral uptake, metabolic disorders, damages from the increased production of reactive oxygen species, and many other disruptions. Plants utilize drought resistance mechanisms as a defense strategy, and the systems’ activation is dependent upon several factors, including plant genotype, onthogenesis phase, drought intensity and duration, and the season in which the drought occurs. Impatiens walleriana is a worldwide popular flowering plant recognized for its vibrant flower colors, and is an indispensable plant in pots, gardens and other public areas. It prefers well-draining, moisturized soil, and does not perform well in overly dry or waterlogged conditions. Consequently, inadequate water supply is a common problem for this plant during production, transportation, and market placement, which has a substantial impact on plant performance overall. This review article outlines certain features of morphological, physiological, and molecular alterations induced by drought in ornamental, drought-sensitive plant species I. walleriana, as well as research carried out to date with the aim to improve the drought tolerance. Stress proteins aquaporins and dehydrins, whose molecular structure was described for the first time in this plant species, are highlighted specifically for their role in drought stress. Furthermore, the effective improvement of drought tolerance in I. walleriana by exogenous application of Plant Growth Regulators and Plant Growth-Promoting Bacteria is discussed in detail. Finally, this review can provide valuable insights for improving plant resilience and productivity in the face of water scarcity, which is critical for sustainable agriculture and horticulture.

Persistent legacy effects on soil metagenomes facilitate plant adaptive responses to drought.

Both chronic and acute drought alter the composition and physiology of soil microbiomes, with implications for globally important processes including carbon cycling and plant productivity. When water is scarce, selection favors microbes with thicker peptidoglycan cell walls, sporulation ability, and constitutive osmolyte production (Schimel, Balser, and Wallenstein 2007)-but also the ability to degrade complex plant-derived polysaccharides, suggesting that the success of plants and microbes during drought are inextricably linked. However, communities vary enormously in their drought responses and subsequent interactions with plants. Hypothesized causes of this variation in drought resilience include soil texture, soil chemistry, and historical precipitation patterns that shaped the starting communities and their constituent species (Evans, Allison, and Hawkes 2022). Currently, the physiological and molecular mechanisms of microbial drought responses and microbe-dependent plant drought responses in diverse natural soils are largely unknown (de Vries et al. 2023). Here, we identify numerous microbial taxa, genes, and functions that characterize soil microbiomes with legacies of chronic water limitation. Soil microbiota from historically dry climates buffered plants from the negative effects of subsequent acute drought, but only for a wild grass species native to the same region, and not for domesticated maize. In particular, microbiota with a legacy of chronic water limitation altered the expression of a small subset of host genes in crown roots, which mediated the effect of acute drought on transpiration and intrinsic water use efficiency. Our results reveal how long-term exposure to water stress alters soil microbial communities at the metagenomic level, and demonstrate the resulting "legacy effects" on neighboring plants in unprecedented molecular and physiological detail.

BAPID suppresses the inhibition of BRM on Di19-PR module in response to drought.

Drought is one of the most important abiotic stresses, and seriously threatens plant development and productivity. Increasing evidence indicates that chromatin remodelers are pivotal for plant drought response. However, molecular mechanisms of chromatin remodelers-mediated plant drought responses remain obscure. In this study, we found a novel interactor of BRM called BRM-associated protein involved in drought response (BAPID), which interacted with SWI/SNF chromatin remodeler BRM and drought-induced transcription factor Di19. Our findings demonstrated that BAPID acted as a positive drought regulator since drought tolerance was increased in BAPID-overexpressing plants, but decreased in BAPID-deficient plants, and physically bound to PR1, PR2, and PR5 promoters to mediate expression of PR genes to defend against dehydration stress. Genetic approaches demonstrated that BRM acted epistatically to BAPID and Di19 in drought response in Arabidopsis. Furthermore, the BAPID protein-inhibited interaction between BRM and Di19, and suppressed the inhibition of BRM on the Di19-PR module by mediating the H3K27me3 deposition at PR loci, thus changing nucleosome accessibility of Di19 and activating transcription of PR genes in response to drought. Our results shed light on the molecular mechanism whereby the BAPID-BRM-Di19-PRs pathway mediates plant drought responses. We provide data improving our understanding of chromatin remodeler-mediated plant drought regulation network.

Examining the Sensitivity of Satellite-Derived Vegetation Indices to Plant Drought Stress in Grasslands in Poland.

In this study, the emphasis is on assessing how satellite-derived vegetation indices respond to drought stress characterized by meteorological observations. This study aimed to understand the dynamics of grassland vegetation and assess the impact of drought in the Wielkopolskie (PL41) and Podlaskie (PL84) regions of Poland. Spatial and temporal characteristics of grassland dynamics regarding drought occurrences from 2020 to 2023 were examined. Pearson correlation coefficients with standard errors were used to analyze vegetation indices, including NDVI, NDII, NDWI, and NDDI, in response to drought, characterized by the meteorological parameter the Hydrothermal Coefficient of Selyaninov (HTC), along with ground-based soil moisture measurements (SM). Among the vegetation indices studied, NDDI showed the strongest correlations with HTC at r = -0.75, R2 = 0.56, RMSE = 1.58, and SM at r = -0.82, R2 = 0.67, and RMSE = 16.33. The results indicated drought severity in 2023 within grassland fields in Wielkopolskie. Spatial-temporal analysis of NDDI revealed that approximately 50% of fields were at risk of drought during the initial decades of the growing season in 2023. Drought conditions intensified, notably in western Poland, while grasslands in northeastern Poland showed resilience to drought. These findings provide valuable insights for individual farmers through web and mobile applications, assisting in the development of strategies to mitigate the adverse effects of drought on grasslands and thereby reduce associated losses.

Influence of Biochar-Reinforced Hydrogel Composites on Growth and Biochemical Parameters of Bean Plants and Soil Microbial Activities under Different Moisture Conditions

Hydrogels have shown promise in improving soil quality and alleviating plant drought stress. This study investigated the effectiveness of four hydrogel composites composed of polyvinyl alcohol, sodium alginate, and pine or olive tree biochar in improving bean (Phaseolus vulgaris) plant growth and soil microbial activities. The experiment was conducted in natural soil, where biochar–hydrogel composites were applied at a concentration of 0.75% hydrogel per soil weight (w/w) for 35 days under two different moisture conditions: adequate moisture (70% of water holding capacity (WHC)) and drought stress (40% WHC). The results showed variation between hydrogel composites and, more importantly, between water regimes. Under water deficit conditions, biochar–hydrogel composites consistently caused a decrease in plant weight and in chlorophyll (CHL) CHLa/CHLb ratio. Furthermore, antioxidant enzyme activities and malondialdehyde and protein levels generally increased in contrast to the observations at 70% WHC. Regarding microbial activities, the composites reduced soil respiration (12–38%) while promoting phosphatase activity (42–65%) under both moisture regimes. Overall, the introduction of hydrogel composites did not show consistently positive effects on either plants or soil microorganisms. To thoroughly evaluate the efficacy of these hydrogels as soil amendments, further studies are needed, considering different soil types, plant species, and hydrogel application rates.

Superabsorbent Polymer Reduces β-ODAP Content in Grass Pea by Improving Soil Water Status and Plant Drought Tolerance

Superabsorbent Polymer Reduces β-ODAP Content in Grass Pea by Improving Soil Water Status and Plant Drought Tolerance

Silencing of GhSINAT5 Reduces Drought Resistance and Salt Tolerance in Cotton.

The SEVEN IN ABSENTIA (SINA) E3 ubiquitin ligase is widely involved in drought and salt stress in plants. However, the biological function of the SINA proteins in cotton is still unknown. This study aimed to reveal the function of GhSINAT5 through biochemical, genetic and molecular approaches. GhSINAT5 is expressed in several tissues of cotton plants, including roots, stems, leaves and cotyledons, and its expression levels are significantly affected by polyethylene glycol, abscisic acid and sodium chloride. When GhSINAT5 was silenced in cotton plants, drought and salinity stress occurred, and the length, area and volume of the roots significantly decreased. Under drought stress, the levels of proline, superoxide dismutase, peroxidase and catalase in the GhSINAT5-silenced cotton plants were significantly lower than those in the non-silenced control plants, whereas the levels of hydrogen peroxide and malondialdehyde were greater. Moreover, the expression of stress-related genes in silenced plants under drought stress suggested that GhSINAT5 may play a positive role in the plant response to drought and salt stress by regulating these stress response-related genes. These findings not only deepen our understanding of the mechanisms of drought resistance in cotton but also provide potential targets for future improvements in crop stress resistance through genetic engineering.

The nonphototrophic hypocotyl 3 (NPH3) domain protein NRL5 is a trafficking-associated GTPase essential for drought resistance.

The mechanisms of plant drought resistance are unclear but may involve membrane trafficking and metabolic reprogramming, including proline accumulation. Forward genetic screening using a proline dehydrogenase 1 (ProDH1) promoter:reporter identified a drought hypersensitive mutant with a single-amino acid substitution (P335L) in the nonphototrophic hypocotyl 3 (NPH3) domain of NPH3/root phototropism 2-like 5 (NRL5)/naked pins in Yucca 8 (NPY8). Further experiments found that NRL5 and other NPH3 domain proteins are guanosine triphosphatases (GTPases). NRL5, but not NRL5P335L, interacted with the RABE1c and RABH1b GTPases and the soluble N-ethylmaleimide-sensitive factor attachment protein receptors (SNAREs) Vesicle-Associated Membrane Protein (VAMP)721/722. These proteins controlled NRL5 localization and connection to trafficking while also being genetically downstream of, and potentially regulated by, NRL5. These data demonstrate that NRL5-mediated restraint of proline catabolism is required for drought resistance and also reveal unexpected functions of the NPH3 domain such that the role of NPH3 domain proteins in signaling, trafficking, and cellular polarity can be critically reevaluated.

Genome-Wide Identification of Caffeic Acid O-Methyltransferase Gene Family in Medicago truncatula: MtCOMT13-Mediated Salt and Drought Tolerance Enhancement

Legumes are important grains and forages, providing high-quality proteins, vitamins, and micronutrients to humans and animals. Medicago truncatula is a close relative of alfalfa (Medicago sativa). Caffeic acid O-methyltransferase (COMT), a key gene that is identified to be essential for melatonin synthesis, plays a significant role in plant growth, development, and abiotic stress responses. However, a systematic study on the COMT gene family in M. truncatula has still not been reported. In this study, 63 MtCOMT genes were identified and categorized into three groups. Gene structure and conserved motif analyses revealed the relative conservation of closely clustered MtCOMTs within each group. Duplicated events in MtCOMT members were identified, and segmental duplication was the main mean. Cis-acting element prediction revealed the involvement of MtCOMTs in growth and development and response to light, stress, and plant hormones. RNA-seq data analysis showed that 57 MtCOMTs varied under salt and drought stresses. The RT-qPCR expression patterns showed that MtCOMT9, MtCOMT13, MtCOMT22, MtCOMT24, MtCOMT43, and MtCOMT46 were related to salt and drought responses in M. truncatula. Additionally, Arabidopsis thaliana overexpressing MtCOMT13 displayed superior plant growth phenotypes and enhanced tolerance to salt and drought stresses through higher photosynthetic parameters and activities of antioxidant enzymes, which indicated that MtCOMT13 played an important role in positively regulating plant salt and drought tolerance. These findings contribute to an improved understanding of MtCOMTs’ roles in abiotic stress responses in M. truncatula, providing an important theoretical basis and genetic resource for legume species resistance breeding in the future.

Expression of Foxtail Millet bZIP Transcription Factor SibZIP67 Enhances Drought Tolerance in Arabidopsis.

Foxtail millet is a drought-tolerant cereal and forage crop. The basic leucine zipper (bZIP) gene family plays important roles in regulating plant development and responding to stresses. However, the roles of bZIP genes in foxtail millet remain largely uninvestigated. In this study, 92 members of the bZIP transcription factors were identified in foxtail millet and clustered into ten clades. The expression levels of four SibZIP genes (SibZIP11, SibZIP12, SibZIP41, and SibZIP67) were significantly induced after PEG treatment, and SibZIP67 was chosen for further analysis. The studies showed that ectopic overexpression of SibZIP67 in Arabidopsis enhanced the plant drought tolerance. Detached leaves of SibZIP67 overexpressing plants had lower leaf water loss rates than those of wild-type plants. SibZIP67 overexpressing plants improved survival rates under drought conditions compared to wild-type plants. Additionally, overexpressing SibZIP67 in plants displayed reduced malondialdehyde (MDA) levels and enhanced activities of antioxidant enzymes, including catalase (CAT), superoxide dismutase (SOD), and peroxidase (POD) under drought stress. Furthermore, the drought-related genes, such as AtRD29A, AtRD22, AtNCED3, AtABF3, AtABI1, and AtABI5, were found to be regulated in SibZIP67 transgenic plants than in wild-type Arabidopsis under drought conditions. These data suggested that SibZIP67 conferred drought tolerance in transgenic Arabidopsis by regulating antioxidant enzyme activities and the expression of stress-related genes. The study reveals that SibZIP67 plays a beneficial role in drought response in plants, offering a valuable genetic resource for agricultural improvement in arid environments.

Functional Characterization of the Paeonia ostii P5CS Gene under Drought Stress.

With persistent elevation in global temperature, water scarcity becomes a major threat to plant growth and development, yield security, agricultural sustainability, and food production. Proline, as a key osmolyte and antioxidant, plays a critical role in regulating drought tolerance in plants, especially its key biosynthetic enzyme, delta-1-pyrroline-5-carboxylate synthase (P5CS), which always positively responds to drought stress. As an important woody oil crop, the expansion of Paeonia ostii cultivation needs to address the issue of plant drought tolerance. Here, we isolated a PoP5CS gene from P. ostii, with an open reading frame of 1842 bp encoding 613 amino acids. PoP5CS expression progressively increased in response to increasing drought stress, and it was localized in the cytoplasm. Silencing of PoP5CS in P. ostii reduced drought tolerance, accompanied by decreased proline content, elevated reactive oxygen species (ROS) accumulation, and increased relative electrical conductivity (REC) and malondialdehyde (MDA) levels. Conversely, overexpression of PoP5CS in Nicotiana tabacum plants enhanced drought resistance, manifested by increased proline levels, reduced ROS accumulation, and lower REC and MDA contents. This study isolates PoP5CS from P. ostii and validates its role in regulating drought tolerance, providing valuable genetic resources and theoretical insights for the development of drought-resistant P. ostii cultivars.

Enhanced root system architecture in oilseed rape transformed with Rhizobium rhizogenes

Transformation of plants using wild strains of agrobacteria is termed natural transformation and is not covered by GMO legislation in e.g. European Union and Japan. In the current study, offspring lines (A11 and B3) of Rhizobium rhizogenes naturally transformed oilseed rape (Brassica napus) were randomly selected to characterize the morphological traits, and analyze the implications of such morphological changes on plant drought resilience. It was found that the introduction of Ri-genes altered the biomass partitioning to above- and under-ground parts of oilseed rape plants. Compared to the wild type (WT), the A11 and B3 lines exhibited 1.2–4.0 folds lower leaf and stem dry weight, leaf area and plant height, but had 1.3–5.8 folds greater root dry weight, root length and root surface area, resulting in a significantly enhanced root: shoot dry mass ratio and root surface area: leaf area ratio. In addition, the introduction of Ri-genes conferred reduced stomatal pore aperture and increased stomatal density in the B3 line, and increased leaf thickness in A11 line, which could benefit plant drought resilience. Finally, the modulations in morphological traits as a consequence of transformation with Ri-genes are discussed concerning resilience in water-limited conditions. These findings reveal the potential of natural transformation with R. rhizogenes for drought-targeted breeding in crops.

Influence of the transcription factor ABI5 on growth and development in Arabidopsis

ABA-insensitive 5 (ABI5) belongs to the basic leucine zipper class of transcription factors and is named for being the fifth identified Arabidopsis mutant unresponsive to ABA. To understand the influence of ABI5 in its active state on downstream gene expression and plant growth and development, we overexpressed the full-length ABI5 (A.t.MX-4) and the active forms of ABI5 with deleted transcriptional repression domains (A.t.MX-1, A.t.MX-2, and A.t.MX-3). Compared with the wild type, A.t.MX-1, A.t.MX-2, and A.t.MX-3 exhibited an increase in rosette leaf number and size, earlier flowering, increased thousand-seed weight, and significantly enhanced drought resistance. Thirty-five upregulated/downregulated proteins in the A.t.MX-1 were identified by proteomic analysis, and these proteins were involved in ABA biosynthesis and degradation, abiotic stress, fatty acid synthesis, and energy metabolism. These proteins participate in the regulation of plant drought resistance, flowering timing, and seed size at the levels of transcription and post-translational modification.

Combating Soil Drought in Maize (Zea mays L.): Genetic-Engineering Strategies for Drought Tolerant Varieties

Drought is the global challenge of crop agriculture across the globe. The detrimental effect of drought hinders a significant growth and development impairment leading to devastating harvest losses. Maize, a vital staple for food faces future challenges with a rapidly expanding drought area. To address this challenge, scientists and breeders are urged to develop new varieties that are not only resistant or tolerant but also even potentially thrive under drought planting conditions. New breeding technologies involving molecular biology and biotechnology have been developed and implemented thus offering a promising solution. Genetic engineering has allowed humans to straightforwardly transfer beneficial genes across species and varieties, thus deliberating gene pool transfer of similar species and varieties. Furthermore, this technology has evolved to the level of creation, deletion, or modification of existing alleles with high precision through CRISPR/Cas9-mediated genome editing. This review article delves into the morpho-physiology, biochemical, and molecular responses of maize varieties against drought stress. It subsequently explores how genetic engineering has been utilized to optimize the selected genes underlying those responses. By exploring the current progress of genetic engineering, this article aims to prepare the ground for future advancement in combating drought through drought-tolerant maize varieties. Thus, this review article has the potential to contribute to improving food security in the increasing drought challenges.

Epigenetic Modifications of Hormonal Signaling Pathways in Plant Drought Response and Tolerance for Sustainable Food Security.

Drought significantly challenges global food security, necessitating a comprehensive understanding of plant molecular responses for effective mitigation strategies. Epigenetic modifications, such as DNA methylation and histone modifications, are key in regulating genes and hormones essential for drought response. While microRNAs (miRNAs) primarily regulate gene expression post-transcriptionally, they can also interact with epigenetic pathways as potential effectors that influence chromatin remodeling. Although the role of miRNAs in epigenetic memory is still being explored, understanding their contribution to drought response requires examining these indirect effects on epigenetic modifications. A key aspect of this exploration is epigenetic memory in drought-adapted plants, offering insights into the transgenerational inheritance of adaptive traits. Understanding the mechanisms that govern the maintenance and erasure of these epigenetic imprints provides nuanced insights into how plants balance stability and flexibility in their epigenomes. A major focus is on the dynamic interaction between hormonal pathways-such as those for abscisic acid (ABA), ethylene, jasmonates, and salicylic acid (SA)-and epigenetic mechanisms. This interplay is crucial for fine-tuning gene expression during drought stress, leading to physiological and morphological adaptations that enhance plant drought resilience. This review also highlights the transformative potential of advanced technologies, such as bisulfite sequencing and CRISPR-Cas9, in providing comprehensive insights into plant responses to water deficit conditions. These technologies pave the way for developing drought-tolerant crops, which is vital for sustainable agriculture.

Transcription factor TaNF-YB2 interacts with partners TaNF-YA7/YC7 and transcriptionally activates distinct stress-defensive genes to modulate drought tolerance in T. Aestivum

BackgroundDrought stress limits significantly the crop productivity. However, plants have evolved various strategies to cope with the drought conditions by adopting complex molecular, biochemical, and physiological mechanisms. Members of the nuclear factor Y (NF-Y) transcription factor (TF) family constitute one of the largest TF classes and are involved in plant responses to abiotic stresses.ResultsTaNF-YB2, a NY-YB subfamily gene in T. aestivum, was characterized in this study focusing on its role in mediating plant adaptation to drought stress. Yeast two-hybrid (Y-2 H), biomolecular fluoresence complementation (BiFC), and Co-immunoprecipitation (Co-IP) assays indicated that TaNF-YB2 interacts with the NF-YA member TaNF-YA7 and NF-YC family member TaNF-YC7, which constitutes a heterotrimer TaNF-YB2/TaNF-YA7/TaNF-YC7. The TaNF-YB2 transcripts are induced in roots and aerial tissues upon drought signaling; GUS histochemical staining analysis demonstrated the roles of cis-regulatory elements ABRE and MYB situated in TaNF-YB2 promoter to contribute to target gene response to drought. Transgene analysis on TaNF-YB2 confirmed its functions in regulating drought adaptation via modulating stomata movement, osmolyte biosynthesis, and reactive oxygen species (ROS) homeostasis. TaNF-YB2 possessed the abilities in transcriptionally activating TaP5CS2, the P5CS family gene involving proline biosynthesis and TaSOD1, TaCAT5, and TaPOD5, the genes encoding antioxidant enzymes. Positive correlations were found between yield and the TaNF-YB2 transcripts in a core panel constituting 45 wheat cultivars under drought condition, in which two types of major haplotypes including TaNF-YB2-Hap1 and -Hap2 were included, with the former conferring more TaNF-YB2 transcripts and stronger plant drought tolerance.ConclusionsTaNF-YB2 is transcriptional response to drought stress. It is an essential regulator in mediating plant drought adaptation by modulating the physiological processes associated with stomatal movement, osmolyte biosynthesis, and reactive oxygen species (ROS) homeostasis, depending on its role in transcriptionally regulating stress response genes. Our research deepens the understanding of plant drought stress underlying NF-Y TF family and provides gene resource in efforts for molecular breeding the drought-tolerant cultivars in T. aestivum.

Photosynthetic Performance, Carbohydrate Partitioning, Growth, and Yield among Cassava Genotypes under Full Irrigation and Early Drought Treatment in a Tropical Savanna Climate.

In a tropical savanna climate like Thailand, cassava can be planted all year round and harvested at 8 to 12 months after planting (MAP). However, it is not clear how water limitation during the dry season without rain affects carbon assimilation, partitioning, and yield. In this field investigation, six cassava genotypes were planted in the rainy season (August 2021) under continuous irrigation (control) or subjected to drought for 60 days from 3MAP to 5MAP during the dry season (November 2021 to January 2022) with no irrigation and rainfall. After that, the plants were rewatered and continued growing until harvest at 12MAP. After 60 days of stress, there were significant reductions in the mean net photosynthesis rate (Pn), petiole, and root dry weight (DW), and slight reductions in leaf, stem, and tuber DW. The mean starch concentrations were reduced by 42% and 16% in leaves and tubers, respectively, but increased by 12% in stems. At 6MAP after 30 days of rewatering, Pn fully recovered, and stem starch was remobilized resulting in a dramatic increase in the DW of all the organs. Although the mean tuber DW of the drought plants at 6MAP was significantly lower than that of the control, it was significantly higher at 12MAP. Moreover, the mean tuber starch concentration at 12MAP of the drought plants (18.81%) was also significantly higher than that of the controls (16.46%). In the drought treatment, the high-yielding varieties, RY9, RY72, KU50, and CMR38-125-77 were similarly productive in terms of tuber DW and starch concentration while the breeding line CM523-7 produced the lowest tuber biomass and significantly lower starch content. Therefore, for cassava planted in the rainy season in the tropical savanna climate, the exposure to drought during the early growth stage was more beneficial than the continuous irrigation.

ZmDST44 Gene Is a Positive Regulator in Plant Drought Stress Tolerance.

Improving drought tolerance in plants is essential for increasing crop yields under water-limited conditions. In this study, we investigated the functional role of the maize gene ZmDST44, which is targeted by the miRNA ZmmiR139. Our results indicate that ZmmiR139 regulates ZmDST44 by cleaving its mRNA, as confirmed by inverse expression patterns and 5'-RACE analysis. Overexpression of ZmDST44 in Arabidopsis, rice, and maize resulted in significant enhancements in drought tolerance. Transgenic plants exhibited reduced malondialdehyde (MDA) levels, increased proline accumulation, and upregulation of drought-responsive genes compared to wild-type plants. Transgenic Arabidopsis and rice showed improved drought resistance and higher post-drought recovery rates, and transgenic maize displayed lower sensitivity to drought stress. These findings suggest that ZmDST44 acts as a positive regulator of drought tolerance across different plant species and holds promise for developing drought-resistant crops through genetic engineering.