Drought Stress Research Articles

Identification of candidate genes for improving phosphorus use efficiency in a cowpea (Vigna unguiculata (L.) Walp.) multi-parent advanced generation inter-cross (MAGIC) population

Cowpea (Vigna unguiculata (L.) Walp.) is the most important grain legume in sub-Saharan Africa where it provides a significant source of human nutrition and animal fodder to millions of low-input farmers. While adapted to a wide range of soils and generally considered climate resilient due to its drought and heat tolerance, cowpea yields are suboptimal throughout its main growing region because of numerous abiotic and biotic stress factors and low soil fertility. Among the major limitations is low available soil phosphorus (P) and, therefore, improving cowpea cultivars for growth under limiting P conditions would be of great importance and benefit to local low-input farmers. We grew a multi-parent advanced generation inter-cross (MAGIC) population of cowpea consisting of 305 F8 recombinant inbred lines (RILs) generated from eight genetically diverse founder parents and phenotyped them for root system, shoot system, and total biomass production under normal and low phosphate conditions in an ebb and flow hydroponic system. We then performed a genome wide association study (GWAS) to identify genes associated with phosphorus use efficiency (PUE). Two SNPs were identified that are significantly associated with shoot system growth under phosphate stress: one located on chromosome Vu09 and the other on Vu10. A third SNP was identified on Vu03 that is associated with enhanced root production under phosphate stress. Characterizing the underlying genetic basis for PUE can assist in the improvement of cowpea for better productivity across Africa.

Mechanistic modeling of root water uptake in tropical agriculture: a sensitivity analysis of drought stress dynamics

Mechanistic modeling of root water uptake in tropical agriculture: a sensitivity analysis of drought stress dynamics

RTN family and its response to abiotic stress in Oryza sativa

Abiotic stresses induced by climate change and soil pollution cause significant crop yield loss. Identifying stress-resistant genes for genetic improvement is urgent and necessary. Reticulon (RTN, also called RTNLB in plants) is a widely distributed endoplasmic reticulum-associated protein in eukaryotic cells, playing a crucial role in stress response activities, including autophagy, endoplasmic reticulum stress, and osmotic regulation. However, the diversity of RTNLBs in plants has hindered comprehensive analysis. This study identified 20 OsRTNLBs from Oryza sativa through a comprehensive whole-genome analysis. Detailed information on their chromosomal localization, protein motifs, phylogenetic relationships, and gene collinearity has been provided. The effects of five major abiotic stresses—cold, heat, heavy metals, salt, and drought—on rice seedling development have been assessed. The expression levels of RTNLBs under these abiotic stresses show significant changes, with an overall increase in transcription levels under simulated drought stress and a decrease under the other four stresses. Three OsRTNLBs (OsRTNLB4, OsRTNLB8 and OsRTNLB9) have been identified as key proteins contributing to abiotic stress.

Quantitative proteomic analysis based on TMT reveals different responses of Haloxylon ammodendron and Haloxylon persicum to long-term drought

The essence of the plant drought tolerance mechanism lies in determining protein expression patterns, identifying key drought-tolerant proteins, and elucidating their association with specific functions within metabolic pathways. So far, there is limited information on the long-term drought tolerance of Haloxylon ammodendron and Haloxylon persicum grown in natural environments, as analyzed through proteomics. Therefore, this study conducted proteomic research on H. ammodendron and H. persicum grown in natural environments to identify their long-term drought-tolerant protein expression patterns. Totals of 71 and 348 differentially expressed proteins (DEPs) were identified in H. ammodendron and H. persicum, respectively. Bioinformatics analysis of DEPs reveals that H. ammodendron primarily generates a large amount of energy by overexpressing proteins related to carbohydrate metabolism pathways (pyruvate kinase, purple acid phosphatases and chitinase), and simultaneously encodes proteins capable of degrading misfolded/damaged proteins (tam3-transposase, enhancer of mRNA-decapping protein 4, and proteinase inhibitor I3), thus adapting to long-term drought environments. For H. persicum, most DEPs (enolase and UDP-xylose/xylose synthase) involved in metabolic pathways are up-regulated, indicating that it mainly adapts to long-term drought environments through mechanisms related to positive regulation of protein expression. These results offer crucial insights into how desert plants adapt to arid environments over the long term to maintain internal balance. In addition, the identified key drought-tolerant proteins can serve as candidate proteins for molecular breeding in the genus Haloxylon, aiming to develop new germplasm for desert ecosystem restoration.

Bacillus megaterium GEB3 reduces accumulation of reactive oxygen species and enhances drought tolerance in peppers

Plant growth-promoting rhizobacteria regulate plant growth and stress tolerance by modulating endogenous developmental and physiological processes. This study examined the role of Bacillus megaterium GEB3 in affecting drought stress tolerance in peppers. GEB3 treatment significantly mitigated drought-induced symptoms, such as chlorosis, wilting, and leaf rolling, in both vegetative- and reproductive-stage peppers. For example, GEB3 treatment increased the number of fruits and total fruit weight by approximately 34% and 68%, respectively, compared to those in untreated control plants. We observed that GEB3 treatment reduces drought-induced reactive oxygen species (ROS) accumulation while increasing the transcriptional expression of antioxidant genes encoding peroxidases and superoxide dismutases, which are responsible for ROS removal. Furthermore, GEB3 activated the jasmonic acid (JA) response, and JA treatment alone was sufficient to reduce the accumulation of ROS and enhance pepper tolerance to drought stress. These findings suggest that Bacillus megaterium GEB3 increases drought tolerance in peppers through JA-mediated suppression of ROS accumulation, and may serve as a promising bioinoculant for improving crop tolerance against environmental stresses including drought.

Impact of Green Synthesis of Silver Nanoparticles on Antioxidant Activity in Drought-Sensitive and Drought-Tolerant Pimpinella anisum L.

The rapid advancement and evolution of nanotechnology have raised concerns about the potential release of nanoparticles (NPs) into the environment. Since plants are vital components of ecosystems, they play a crucial role in interacting with these substances. This study is the first to investigate how green-labeled silver nanoparticles (AgNPs) affect the activity of three key antioxidant enzymes: catalase (CAT), superoxide dismutase (SOD), and guaiacol peroxidase (GPOx), in anise (Pimpinella anisum L.). Two varieties of anise were examined: drought-sensitive (DS) and drought-tolerant (DT). These plants were exposed to varying concentrations of AgNPs (1, 5, and 10 mg/L) for 21 and 28 days. The results showed no significant difference in CAT activity across all AgNP concentrations for both cultivars. However, SOD activity increased significantly in DT plants treated with 5 mg/L AgNPs for 21 days. In contrast, SOD activity at other concentrations and exposure durations did not yield statistically significant results. For GPOx activity, DT plants exhibited a significant increase after 21 days at both 1 mg/L and 5 mg/L AgNPs. Results at other concentrations varied and were not statistically significant according to the exposure duration and plant variety. Overall, this study suggests that the increased enzyme activity at low AgNP concentrations in DT plants after 21 days indicates an acceptable, harmless level of toxicity. These findings underscore the complexity of AgNP effects on antioxidant enzyme activity in anise plants, highlighting the need for further investigation into the underlying mechanisms and long-term effects of AgNP exposure on plant antioxidant defense systems.

Genome-wide identification and functional analyses of the TCP gene family in Carthamus tinctorius L.

TCP transcription factors play crucial roles in regulating plant growth, development, and the response to abiotic stress. However, members of the TCP family in Carthamus tinctorius L. have not been reported yet. To address this, we conducted a genome-wide analysis of the TCP gene family in C. tinctorius. By using bioinformatics tools and transcriptome data, we identified 22 CtTCP genes unevenly distributed across 7 chromosomes. Collinear relationships were found in 13 genes pairs, and 14 genes involved in whole-genome or segmental duplication events. Amino acid sequence alignment and phylogenetic analysis classified CtTCP into Class I (PCF) and Class II (CIN and CYC/TB1). The motifs and gene structures within each subgroup were similar, and each subgroup contained unique motifs. Additionally, CtTCP1,3,22 were confirmed to localize in the nucleus as predicted. On the basis of transcriptome data and phylogenetic analysis, CtTCP5 and CtTCP4 may play significant roles in the development of C. tinctorius leaves and flowers, respectively. Meanwhile, CtTCP4,11,12,15 might influence the formation of red petals in C. tinctorius. qRT‒PCR analysis showed that the expression of most CtTCP genes were upregulated after exposure to ABA, drought, salt and cold stresses. Specifically CtTCP1, 3, 5 were shown to play important roles in adverse stress. This study provides insights into the functions of CtTCP genes and their potential for improving stress tolerance and flower color in C. tinctorius. Future research should focus on functional validation and breeding applications.

Greater Resistance to Drought-Induced Embolism Is Linked to Higher Yield Maintenance in Soybean.

With increasing drought events worldwide, crop breeding must focus on drought resistance to maintain crop yields. To ensure a high level of gas exchange and growth, plants need to maintain the integrity of their vascular system under drought conditions. While the impact of drought-induced vascular damage on tree species is well-documented, its effect on the yield of annual crops like soybean (Glycine max (L.) Merrill) remains unknown. We investigated xylem vulnerability to embolism of ten soybean cultivars with contrasting phylogenetic origins and phenology using the optical technique. With X-ray micro-tomography, we assessed xylem vulnerability across the plant vascular pathway to quantify the vulnerability segmentation. Our results revealed that soybean is moderately vulnerable to xylem embolism (mean leaf P50 = -1.85 MPa), with a significant Intraspecific variability with a difference of 1 MPa between the most extreme cultivars. Cultivars with higher leaf embolism resistance maintained higher yields in the field, particularly during dry years, highlighting the critical role of xylem hydraulic failure during drought in crop yield. This study provides new insights into the importance of hydraulic traits underlying drought tolerance in soybeans and their incorporation into breeding programmes for embolism resistance to improve yield resilience.

Mechanisms of Salt and Drought Stress Responses in Foxtail Millet

Mechanisms of Salt and Drought Stress Responses in Foxtail Millet

Field application of beneficial microbes to ameliorate drought stress in maize

Field application of beneficial microbes to ameliorate drought stress in maize

Climate-driven variation in the phenology of juvenile Ixodes pacificus on lizard hosts

BackgroundEctothermic arthropods, like ticks, are sensitive indicators of environmental changes, and their seasonality plays a critical role in the dynamics of tick-borne disease in a warming world. Juvenile tick phenology, which influences pathogen transmission, may vary across climates, with longer tick seasons in cooler climates potentially amplifying transmission. However, assessing juvenile tick phenology is challenging in arid climates because ticks spend less time seeking for blood meals (i.e. questing) due to desiccation pressures. As a result, traditional collection methods like dragging or flagging are less effective. To improve our understanding of juvenile tick seasonality across a latitudinal gradient, we examined Ixodes pacificus phenology on lizards, the primary juvenile tick host in California, and explored how climate factors influence phenological patterns.MethodsBetween 2013 and 2022, ticks were removed from 1527 lizards at 45 locations during peak tick season (March–June). Tick counts were categorized by life stage (larvae and nymphs) and linked with remotely sensed climate data, including monthly maximum temperature, specific humidity and Palmer Drought Severity Index (PDSI). Juvenile phenology metrics, including tick abundances on lizards, Julian date of peak mean abundance and temporal overlap between larval and nymphal populations, were analyzed along a latitudinal gradient. Generalized additive models (GAMs) were applied to assess climate-associated variation in juvenile abundance on lizards.ResultsMean tick abundance per lizard ranged from 0.17 to 47.21 across locations, with the highest abundance in the San Francisco Bay Area and lowest in Los Angeles, where more lizards had zero ticks attached. In the San Francisco Bay Area, peak nymphal abundance occurred 25 days earlier than peak larval abundance. Temporal overlap between larval and nymphal stages at a given location varied regionally, with northern areas showing higher overlap, possibly due to the bimodal seasonality of nymphs. We found that locations with higher temperatures and increased drought stress were linked to lower tick abundances, although the magnitude of these effects depended on regional location.ConclusionsOur study, which compiled 10 years of data, reveals significant regional variation in juvenile I. pacificus phenology across California, including differences in abundance, peak timing, and temporal overlap. These findings highlight the influence of local climate on tick seasonality, with implications for tick-borne disease dynamics in a changing climate.Graphical

ZmCIPK33 and ZmSnRK2.10 mutually reinforce the abscisic acid signaling pathway for combating drought stress in maize.

The calcineurin B-like protein (CBL)-CBL-interacting protein kinase (CIPK) Ca²⁺ sensors play crucial roles in the plant's response to drought stress. However, there have been few reports on the synergistic regulation of drought stress by CBL-CIPK and abscisic acid (ABA) core signaling components. In this study, we discovered that ZmCIPK33 positively regulates drought resistance in maize. ZmCIPK33 physically interacts with and is enhanced by phosphorylation from ZmSnRK2.10. Drought stress can activate ZmCIPK33, which is partially dependent on ZmSnRK2.10. ZmCIPK33 in combination with ZmSnRK2.10 can activate the slow anion channel ZmSLAC1 in Xenopus laevis oocytes independently of CBLs, whereas ZmCIPK33 or ZmSnRK2.10 alone is unable to do so. Furthermore, ZmCIPK33 phosphorylates ZmPP2C11 at Ser60, which leads to a reduction in the interaction between ZmPP2C11 and ZmEAR1 (the ortholog of Arabidopsis Enhancer of ABA co-Receptor 1) and weakens the phosphatase activity of ZmPP2C11, consequently, enhancing the activity of ZmSnRK2.10 in an in vitro assay and in the in-gel assay of the zmcipk33 mutant. Our findings provide novel insightsinto the molecular mechanisms underlying the reciprocal enhancement of Ca²⁺ and ABA signaling under drought stress in maize.

The drought-responsive wheat AP2/ERF transcription factor TaRAP2-13L and its interacting protein TaWRKY10 enhance drought tolerance in transgenic Arabidopsis and wheat (Triticum aestivum L.).

The drought-responsive wheat AP2/ERF transcription factor TaRAP2-13L and its interacting protein TaWRKY10 enhance drought tolerance in transgenic Arabidopsis and wheat (Triticum aestivum L.).

CsSAD1-silenced in tea leaves impaired drought tolerance by decreasing plasma membrane H +-ATPase activity.

Drought stress is a negative regulatory factor that leads to reduced yield and quality. Unsaturated fatty acids controlled by SAD (stearic acid desaturase) play a key role in mediating membrane fluidity to cope with drought stress; however, the response of CsSAD1 to drought stress is poorly understood. In this study, CsSAD1-silenced leaves displayed weakened drought tolerance, accompanied by lower Fv/Fm and higher MDA levels. However, CsSAD1-overexpressing Arabidopsis exhibited an elevated tolerance to drought stress in pot experiments. Furthermore, CsSAD1-silenced leaves displayed reduced plasma membrane H+-ATPase activity, which promoted membrane potential depolarization and led to a massive K+ loss under PEG stress. In contrast, CsSAD1-overexpressing Arabidopsis showed higher plasma membrane H+-ATPase activity and alleviated membrane potential depolarization, which in turn mitigated K+ loss under drought stress. Moreover, an exogenous supply of Na3VO4 (P-type ATPases inhibitor) further indicated that the difference in K+ efflux in the transgenic plants was dependent on the plasma membrane H+-ATPase. Therefore, silencing CsSAD1 in tea leaves inhibited plasma membrane H+-ATPase activity, which was the primary factor contributing to the maintenance of K+ homeostasis and, consequently, drought tolerance in tea plants.

Unravelling the combined effects of drought and nitrogen addition on carbon assimilation and reserves in Korean pine saplings

Climate change profoundly impacts the physiological processes and adaptation strategies of plants. However, the physiological mechanisms of coniferous species responding and adapting to combined drought and nitrogen (N) addition remain unclear. Here, based on 2-year multi-level N addition and drought experiments, we investigated the responses of carbon assimilation (net photosynthetic rate An, stomatal conductance gs and intrinsic water use efficiency WUEi) and carbon reserves (non-structural carbohydrates, NSC) of 7-year-old Korean pine (Pinus koraiensis) saplings. Our results showed that: (1) Drought decreased An and gs, while N addition increased An and decreased gs. N addition decreased An and WUEi but increased gs in plants under drought conditions, indicating that N addition under drought stress will maintain gas exchange by increasing stomatal opening, but failed to mitigate the reduction of An. (2) Both drought (moderate and severe) and N addition reduced leaf NSC concentrations. Under moderate drought stress, however, N addition led to an increase in leaf NSC concentrations. (3) The interconversion between leaf starch and soluble sugars slowed the decrease in carbon assimilation caused by drought. P. koraiensis saplings adopted a conservative strategy of increasing leaf mass per area (LMA) to adapt to reduced water use efficiency. The study highlights the coordinated relationship between carbon assimilation and carbon reserves of Korean pine saplings under combined drought and N addition, which improves our understanding of the diverse carbon dynamics of different species under climate change.

High-quality genome of allotetraploid Avena barbata provides insights into the origin and evolution of B subgenome in Avena.

Avena barbata, a wild oat species within the genus Avena, is a widely used model for studying plant ecological adaptation due to its strong environmental adaptability and disease resistance, serving as a valuable genetic resource for oat improvement. Here, we phased the high-quality chromosome-level genome assembly of A. barbata (6.88 Gb, contig N50 = 53.74 Mb) into A (3.57 Gb with 47,687 genes) and B (3.31 Gb with 46,029 genes) subgenomes. Comparative genomics and phylogenomic analyses clarified the evolutionary relationships and trajectories of A, B, C and D subgenomes in Avena. We inferred that the A subgenome donor of A. barbata was Avena hirtula, while the B subgenome donor was probably an extinct diploid species closely related to Avena wiestii. Genome evolution analysis revealed the dynamic transposable element (TE) content and subgenome divergence, as well as extensive structure variations across A, B, C, and D subgenomes in Avena. Population genetic analysis of 211 A. barbata accessions from distinct ecotypes identified several candidate genes related to environmental adaptability and drought resistance. Our study provides a comprehensive genetic resource for exploring the genetic basis underlying the strong environmental adaptability of A. barbata and the molecular identification of important agronomic traits for oat breeding.

Screening Chili and Sweet Pepper Lines for Drought Tolerance and Hybrid Vigor for Leaf, Stem, and Fruit Quality Traits

Pepper (Capsicum annuum) is an important vegetable commodity grown in Florida. We are focused on developing improved pepper cultivars adapted to field production. For this purpose, we needed quick and efficient methods to screen large number of breeding lines for plant and fruit quality traits. Loss of water from leaves through transpiration is one aspect of whole plant tolerance to drought. To test variation in this trait, we screened 8 inbred lines grown in a greenhouse for the rate of water loss from excised leaves. In a 30-minute incubation period under light, excised leaves from the lines lost 13% (‘Georgia Flame’) to 19% (‘Corno di Toro’) of the initial water suggesting that this screen could be an efficient way to identify germplasm to test for whole plant tolerance to drought. To understand the degree of hybrid vigor of F1 peppers for leaf size, stem branching and fruit quality traits, controlled pollinations between pairs of plants selected from three sweet pepper inbred lines and four chili pepper inbred lines were made. Distinctly different traits in these lines for leaf size, stem branching and fruit size and shape characteristics were recorded. We expect that the methods developed in this research will improve the efficiency in pepper breeding.

A New Aerosol-Based Photobioreactor for the Cultivation of Cyanobacteria on Luffa.

Cyanobacteria are promising organisms for sustainable biotechnology due to their ability to grow photoautotrophically and their wide range of products. Many cyanobacteria grow in the form of biofilms, which is why the development of photobioreactors (PBR) for the cultivation of cyanobacteria in the form of biofilms is of great interest. However, these biofilm PBR are mostly based on artificial growth surfaces, whereas biodegradable growth surfaces would be favored in terms of sustainable production and application. Luffa sponges (the dried fruit of Luffa cylindrica) are excellent biodegradable growth surfaces for cyanobacteria. Therefore, a biofilm PBR for cultivation of cyanobacteria on Luffa was developed in this study. Since many cyanobacteria grow naturally as biofilms in an air-exposed form and this should be imitated to improve growth, an aerosol-based PBR (abPBR) should be used for cultivation. This involves supplying the cyanobacteria with a nutrient mist. The abPBR was comprehensively characterized by determining the distribution of light, humidity and temperature inside the reactor. In addition, the residence time distribution of the aerosol was determined both experimentally and simulatively. In final cultivation experiments, it was shown that the abPBR is ideal for cultivating cyanobacteria and at the same time the aerosol system enables a simple imitation of drought stress. With the cyanobacteria Nostoc spec. and Desmonostoc muscorum, maximum area-time-yields (ATY) in relation to the growth surface of 6.34 and 4.19 g m-2 d-1, respectively, were achieved. Compared to previously developed abPBR, the ATY has been increased by a factor of 2.3.

Sustainable Cotton Production in the Era of Climate Change: Challenges and Adaptive Measures

Climate change is impacting agriculture, particularly cropping systems, in Pakistan due to rising temperatures and changing precipitation patterns. The cultivation of cotton (Gossypium spp.), a globally significant fiber crop, is becoming increasingly vulnerable to the adverse impacts of climate change. Cotton crops face various stresses due to climate change, including extreme temperature stress, drought stress, and salinity stress. Elevated temperatures during the reproductive phase of cotton adversely affect its growth and productivity by disrupting critical physiological processes, including germination, root development, and fruit formation. Similarly, drought stress remains a major limiting factor, particularly in arid and semi-arid regions where cotton is predominantly cultivated, resulting in suppressed plant growth and significant yield losses. Plants employ their mechanisms to adapt to drought conditions, but excessive moisture can also negatively impact growth and yield. Excessive salts in the soil profile and irrigation water trigger salinity stress, which adversely impacts cotton’s vegetative and reproductive growth, with young seedlings being especially sensitive. Air pollution stress, particularly ozone, can damage cotton plants, affecting yield and photosynthetic efficiency. Sustainable management practices, including mulching, cover cropping, and improved irrigation, play a pivotal role in minimizing stress-induced losses in cotton. Simultaneously, breeding for enhanced heat and drought tolerance is imperative for cultivar development. The chapter underlines the crucial role of water management, timely irrigation scheduling, and the strategic use of plant growth regulators (PGRs) in optimizing cotton productivity. Furthermore, the application of Decision Support Systems (DSS) and ICT tools supports efficient resource utilization and improves cotton growers' capacity to adapt to climatic challenges. Climate-smart agriculture (CSA) practices, aimed at boosting productivity, enhancing adaptability to climatic stresses, and curbing greenhouse gas emissions, are crucial for the sustainability of cotton farming. Climate-smart cotton practices and technologies can enhance production, improve farmers' livelihoods, and mitigate the adverse impacts of climate change on cotton cultivation. Adopting a climate-smart cotton production system is crucial for ensuring the sustainability of cotton cultivation in the face of the climate change challenges of this era.

Alleviating Drought Stress Tolerance in Sensitive Genotype of Wheat (Triticum aestivum L.) Through Exogenous Application of Root Exudates

ABSTRACT Root exudates play pivotal roles in supporting plant growth and conferring abiotic stress tolerance to plants. However, reports on their role in drought stress tolerance in wheat are scanty. Citric acid, succinic acid, magnesium, and calcium were previously examined for their increased accumulation in the rhizosphere of drought-tolerant bread wheat (Triticum aestivum L.) genotypes, and their impact on drought stress tolerance in sensitive bread wheat genotype was studied in the current work. Under 15% polyethylene glycol induced water stress condition, succinic acid at 600 ppm, and citric acid (CA) and magnesium sulfate (MgSO4) each at 900 ppm, significantly enhanced the plant height, root length, and fresh and dry weight of plants after 40 days of sowing under controlled conditions. Under water limiting condition in pots, two-time application of CA at 1200 ppm affected majority of the physiological parameters, while CA at 800 ppm positively influenced the grain yield (58.40%) and yield-related parameters. MgSO4 at 400 ppm also supported higher grain yield by 47.29% over control. Under sufficient water condition, CA and MgSO4 each at 400 ppm significantly enhanced the grain yield by 92.25 and 105.37%, respectively, compared to control. Under rain-fed condition in field, two-time application of CA and MgSO4 at 800 ppm and 400 ppm, respectively, significantly enhanced the grain yield by 15.38%, and other grain yield-related parameters. The presence of root exudates under drought stress conditions is thought to improve plant osmoregulation, lower reactive oxygen species, and increase photosynthetic rates.