Function of ABA in Stomatal Defense against Biotic and Drought Stresses

CRISPR-Cas9-mediated editing of ZmPL1 gene improves tolerance to drought stress in maize

Maize (Zea mays L.) is a widely grown food crop around the world. Drought stress seriously affects the growth and development process of plants and causes serious damage to maize yield. In the early stage, our research group conducted transcriptome sequencing analysis on the drought-resistant maize inbred line H8186 and screened out a gene with significantly down-regulated expression, Phylloplanin-like (ZmPL1). The ZmPL1 gee expression pattern was analyzed under various abiotic stresses, and the results showed that this gene was greatly affected by drought stress. Subcellular localization analysis showed that the protein was localized on the cell membrane. In order to verify the role of ZmPL1 in drought stress, we overexpressed ZmPL1 in yeast and found that the expression of ZmPL1 could significantly increase the drought sensitivity of yeast. Next, ZmPL1 transgenic plants were obtained by infecting maize callus using Agrobacterium-mediated method. Under drought stress, compared with overexpression lines, gene-edited lines had higher germination rate and seedling survival rate, lower accumulation of MDA, relative conductivity and ROS, higher antioxidant enzyme activity, and the expression levels of stress-related genes and ROS scavenging-related genes were significantly increased. Exogenous application of ABA to each lines under drought stress attenuated the damage caused by drought stress on ZmPL overexpressing plants. In summary, ZmPL1 negatively regulates drought tolerance in maize.

The impact of irrigation levels and abscisic acid application on the biochemical profiles of strawberries

This study comprehensively examined the effects of irrigation levels and foliar ABA (absisic acid) applications on the biochemical structure of strawberries. ABA treatments significantly increased the levels of total acid (TA), chlorogenic acid, caffeic acid, ellagic acid, ascorbic acid, sucrose, glucose, fructose, and total soluble solids (TSS), all of which are important for fruit quality. Additionally, 50 % deficit irrigation level (Ir50) increased TSS content by 17 %, fructose and glucose by 18 %, sucrose by 11 %, total phenolic content by 27 %, and total antioxidant content by 7 % compared to the full irrigation (Ir100). ABA treatments with Ir50 practices significantly enhanced the concentrations of TA, syringrid acid, ellagic acid, caffeic acid, chlorogenic acid, TSS, fructose, and glucose, which may contribute to the health consciousness of consumers. This study, therefore, highlights the intricate interactions of ABA treatments and irrigation regarding the biochemical profiles of fruits.

Roles and mechanisms of boron in reducing cadmium accumulation in crops

Cadmium (Cd) contamination in farmland soil has become a global environmental concern, resulting in Cd pollution in crops. It is urgent to address this issue, and recent research has suggested that exogenous application of nutrient elements, including boron (B), is an effective strategy to decrease Cd accumulation in crops. Boron, an essential micronutrient for plants, plays a key role in maintaining cell integrity, promoting nitrogen metabolism, and enhancing nutrient absorption. Boron enhances Cd tolerance and reduces Cd accumulation in crops by regulating ROS homeostasis, heavy metal transport proteins, and promoting Cd chelation onto cell walls. However, the precise mechanism by which B regulates Cd accumulation remains unclear. This paper summarizes the physiological, biochemical, and molecular mechanisms by which B regulates Cd accumulation in crops. We believe that the rational application of B in light to moderate Cd-contaminated areas could effectively reduce Cd accumulation in crops, ensuring the safety of agricultural products in these regions.

Lead alters the tolerance of dominant woody plants in subtropical coastal zones to flash drought

Under the influence of climate change and human activities, drought and heavy metal pollution are increasingly threatening the stability of coastal regions. In this study, the ecophysiological responses of three representative coastal plant species (Hibiscus tiliaceus, Barringtonia racemosa, and Terminalia neotaliala) in subtropical regions to lead addition (Pb), drought stress (D), their co-existence (Pb + D), and control (CK) were investigated. The results showed that, compared to CK, Pb treatment alone did not significantly affect plant growth during the experiment, which lasted for 8 days. In contrast, both D and Pb + D treatment caused a notable negative impact, with significant increases in abscisic acid (ABA), proline (PRO), and superoxide anion (O2-) levels and a significant decrease in net photosynthetic rates (Pn). In addition to the comparison with CK, we also observed a distinction between the effects of Pb + D treatment and those of either Pb treatment or D treatment. With Pb + D treatment, Pb accumulation in the roots and leaves of H. tiliaceus and B. racemosa and in the roots of T. neotaliala was higher than those with Pb treatment alone. Other than that, the negative impacts in growth of Pb + D treatment appeared to be delayed compared to the D treatment alone. Moreover, B. racemosa demonstrated good tolerance to Pb, drought and their co-existence treatments, indicating its potential for use in coastal vegetation restoration to enhance ecosystem resilience and stability in subtropical regions.

Synergistic effect of nutrient starvation and abscisic acid on growth and starch accumulation in duckweed

MAIN CONCLUSION

Nutrient starvation and ABA promote starch accumulation in duckweed fronds and turions, enhancing ADP-glucose pyrophosphorylase activity and starch grain size. Duckweed has excellent development potential due to its fast growth, high starch content, and low cellulose content. Nutrient starvation or abscisic acid (ABA) are known to affect growth and starch accumulation in duckweed. However, the joint effects of nutrient starvation and ABA on growth and starch accumulation in duckweed remain unknown. This study analyzed the response of duckweed (Spirodela polyrhiza) to nutrient starvation and ABA and the synergistic treatment of the two to examine the growth and starch accumulation of duckweed. Nutrient starvation and ABA can promote starch accumulation in both the frond and turion of duckweed as a result of the key enzyme ADP-glucose pyrophosphorylase activity that was significantly increased in the starch synthesis pathway of duckweed. Nutrient starvation and ABA can induce the formation of turions with high starch content, which reached up to 38.3 ± 1.9% (dry weight). Further studies on the ultrastructure of the frond and dormant cell of duckweed found that nutrient starvation and ABA increased the number and size of starch grains in duckweed fronds and dormant cells. These results will provide a theoretical basis for duckweed and its turions as a potential renewable energy crop.

Plant PAQR-like sensors activate heterotrimeric G proteins to confer resistance against multiple pathogens

Human adiponectin receptors (AdipoRs) and membrane progestin receptors (mPRs, members of the progestin and adipoQ receptor [PAQR] family) are seven-transmembrane receptors involved in the regulation of metabolism and cancer development, which share structural similarities with G protein-coupled receptors. Plant PAQR-like sensors (PLSs) are homologous to human PAQRs but their molecular functions remain unclear. In this study, we found that PLSs associate with cell surface receptor-like kinases through KIN7 and positively regulate plant immune responses, stomatal defense, and disease resistance. Moreover, PLSs activate heterotrimeric G proteins (Gαβγ) to transduce immune signals and regulate the exchange of GDP for GTP on GPA1. Further analyses revealed that the immune function of PLSs is conserved in rice and soybean and contributes to resistance against multiple diseases. Notably, heterologous expression of human AdipoRs in Arabidopsis replicates the immune functions of PLSs. Collectively, our findings demonstrate that PLSs are key modulators of plant immunity via the G-protein pathway and highlight the potential application of human genes in enhancing plant disease resistance.

Light-driven modulation of plant response to water deficit. A review

The dependence of agriculture on water availability is an important premise justifying attempts to enhance water use efficiency for plant production. Photosynthetic efficiency, directly impacts biomass production, is dependent on both water availability and the quality and quantity of light. Understanding how these factors interact is crucial for improving crop yields. Many overlapping signalling pathways and functions of common bioactive molecules that shape plant responses to both water deficit and light have been identified and discussed in this review. Separate or combined action of these environmental factors include the generation of reactive oxygen species, biosynthesis of abscisic acid, stomatal functioning, chloroplast movement and alterations in the levels of photosynthetic pigments and bioactive molecules. Plant response to water deficit depends on light intensity and its characteristics, with differentiated impacts from UV, blue, and red light bands determining the strength and synergistic or antagonistic nature of interactions. Despite its significance, the combined effects of these environmental factors remain insufficiently explored. The findings highlight the potential for optimising horticultural production through controlled light conditions and regulated deficit irrigation. Future research should assess light and water manipulation strategies to enhance resource efficiency and crop nutritional value.

Comparative transcriptome analysis of Isatis indigotica under different precipitation conditions

BACKGROUND

Plant adaptation to environmental stress is crucial for improving crop resilience and productivity. The growth and yield of Isatis indigotica are significantly affected by water conditions. In this study, high-throughput transcriptome sequencing was performed on leaf samples from Isatis indigotica after different treatments: normal precipitation (CK), 40% rainfall reduction (R1), 80% rainfall reduction (R2), 40% rainfall enhancement (I1) and 80% rainfall enhancement (I2).

RESULTS

Under 80% rainfall augmentation (I2), the malondialdehyde (MDA) content of Isatis indigotica leaves was the lowest, and the proline (pro) and catalase (CAT) activities were the highest. These findings indicate that normal precipitation conditions do not meet the optimal water requirements for the growth of Isatis indigotica and that appropriate irrigation can be used to improve the accumulation and quality of medicinal substances from this species. Transcriptome analysis of Isatis indigotica leaves compared with those in the control group (CK) revealed 896, 2551, 1294, and 3082 differentially expressed genes in the reduced rainfall reduction groups (R1, R2) and increased rainfall groups (I1, 12), respectively. The number of differentially expressed genes (DEGs) gradually increased with increasing rainfall and decreased after rainfall reduction. The GO enrichment results revealed that the DEGs were significantly enriched in functions such as cellular processes, metabolic processes, stimulus response, cell structure, and catalytic and binding activities. KEGG analysis revealed that metabolic pathways such as glutathione metabolism, phenylpropanoid biosynthesis, and plant hormone signaling were significantly enriched, with the greatest number of enriched genes. This study revealed 32 antioxidant system-related genes, 49 phenylpropanoid biosynthesis-related genes, and 49 plant hormone signaling pathway-related genes among the significantly enriched pathways.

CONCLUSIONS

This study provides new insights into the regulation of Isatis indigotica leaves in response to different water contents at the molecular level. The findings also provide a reference for optimizing the field management of Isatis indigotica and improving the quality and yield of medicinal materials.

The regulatory role of phytohormones in plant drought tolerance

MAIN CONCLUSION

This paper highlights the role of various signaling hormones in drought stress tolerance. It explains how phytohormones act and interact under drought conditions. Drought stress significantly impairs plant growth, development and productivity. The likelihood of adverse impacts of drought will increase due to variations in global climate patterns. Phytohormones serve as key regulators of drought tolerance mechanisms in plants. The in-depth understanding of the role and signaling of such hormones is thus of great significance for plant stress management. In this review, we conducted a bibliometric analysis and thematic mapping of recent research on drought and phytohormones, and phytohormone interactions. It is assumed that different classes of phytohormones such as abscisic acid (ABA), auxins (IAA), cytokinins (CTK), ethylene (ETH), gibberellic acid (GA), brassinosteroids (BRs), salicylates (SA), jasmonates (JA), and strigolactones (SLs) play a pivotal role in drought resistance mechanisms in many crops. The present work highlights recent advances in plant responses to drought and uncovers the recent functions of phytohormones in the establishment of drought-specific tolerance strategies. It also deciphers the various interactions between phytohormones allowing plant adaptation to drought stress. Overall, this review highlights recent and original discoveries useful for developing new strategies to improve plant resistance to drought.

Functional analysis of open stomata 1-slow anion channel associated 1-6 protein module in enhancing drought tolerance in tomato through stomatal regulation mechanisms

Tomato (Solanum lycopersicum) is an important vegetable crop, whose growth and development are frequently subjected to drought stress, which severely limits its growth and yield. Identifying key drought-resistance genes in tomato is crucial for elucidating the mechanisms of drought resistance and improving tomato's drought tolerance, which has practical implications for agricultural production. The results of this study demonstrate that silencing SlSLAC1-6 (Slow anion channel associated 1-6) reduces tomato's drought tolerance. SnRK2.6/OST1 (Open stomata 1) protein kinase is a key component in plants' resistance to abiotic stress. Interactions between SlOST1 and SlSLAC1-6 were confirmed through Y2H, BiFC, LCI, Co-IP, and Pull-down assays. Simultaneously, overexpression and knockout of SlOST1 proved that it positively regulates tomato's drought tolerance by influencing reactive oxygen species (ROS) homeostasis, photosynthetic capacity, stomatal closure, and other mechanisms. Silencing SlSLAC1-6 in SlOST1 knockout plants further reduced tomato's drought tolerance. The regulation of tomato drought tolerance by SlOST1 and SlSLAC1-6 highlights the complexity of plant adaptation to drought. These findings provide new insights into the regulatory network of the SlOST1-SlSLAC1 protein module in tomato drought tolerance and offer gene resources for future tomato drought-resistance breeding.

The Class II LBD protein MdLBD37 positively regulates the adaptability of apples to drought and salt stress

Lateral Organ Boundaries Domain (LBD) transcription factors are crucial for plant stress adaptation, yet their functional diversity in perennial crops remains unexplored. In this study, we characterized MdLBD37, a Class II LBD protein in apple (Malus domestica), and identified its key role in enhancing resilience to abiotic stresses. Phylogenetically clustered with anthocyanin repressors AtLBD37/38/39 from Arabidopsis thaliana, MdLBD37 exhibited conserved nuclear localization, supporting its transcriptional regulatory potential. The qRT-PCR analysis revealed that MdLBD37 expression was highest in the stems of 'Royal Gala' apple trees. MdLBD37 expression in apple seedlings was significantly induced by ABA, NaCl, and PEG treatments. Moreover, over-expression of MdLBD37 alleviated the growth inhibition of apple calli under PEG, NaCl, and ABA treatments, marked by increased biomass and reduced MDA accumulation, which suggested a reduction in oxidative damage. These findings not only broaden our understanding of Class II LBD proteins but also establish MdLBD37 as a promising target for developing climate-resilient apple cultivars through modulation of ABA-mediated stress signaling pathways.

Plant chloroplast stress response: insights from mass spectrometry metabolites analysis

Plant chloroplasts produce excess reactive oxygen species (ROS) during photosynthesis, particularly under biotic and abiotic stress conditions. These adverse environmental stresses lead to significant alterations in various cellular components, especially within the chloroplast, which serves as a key stress-sensor organelle. The stress response of chloroplasts can trigger plastid-to-nucleus retrograde signaling and enhance the biosynthesis of biologically active compounds and phytohormones, which are mechanisms that aid plants in acclimating to environmental stress. While ROS act as signaling molecules to help re-adjust cellular metabolic homeostasis, they also risk damaging chloroplasts' structural and functional integrity. Recent research on stress-induced plant metabolism has provided new insights into the chloroplast's stress response. In particular, advancements in mass spectrometry (MS) techniques have expanded our understanding of how oxidative stress affects plants through metabolomics analyses of metabolites involved in this process. Here, we emphasize the MS-based profiling of lipids, apocarotenoids, and phytohormones linked to ROS-triggered processes in plants. Moreover, we discuss the plants' metabolic responses to abiotic stress. Finally, we outline future directions for chloroplast stress research. We advocate for integrating MS-based metabolomics with biochemical and molecular genetic approaches to discover new signaling molecules and identify interconnected signaling components that function across multiple chloroplast signaling pathways.

Genome-Wide Analysis of the JAZ Gene Family in Potato and Functional Verification of StJAZ23 Under Drought Stress

The JASMONATE-ZIM DOMAIN (JAZ) repressors are crucial proteins in the jasmonic acid signaling pathway that play a significant role in plant growth, development and response to abiotic stress (such as drought, heat, salinity, and low temperature). In this study, we identified 26 potato JAZ genes and classified the corresponding predicted proteins into five subfamilies. All potato JAZ proteins exhibited the expected conserved TIFY (TIF[F/Y] XG) and JAZ domains. Additionally, we identified several stress-responsive cis-regulatory elements, notably ABRE and ARE in the promoters of the JAZ gene family. Whole transcriptome and gene family expression analysis identified StJAZ23 as a key gene responding to drought stress in the root tissues of the Atlantic (Atl) and Qingshu 9 (QS9) potato cultivars. The StJAZ23 gene was cloned, and subcellular localization analysis suggested that the StJAZ23 protein was mainly localized in the nucleus and cell membrane. This study confirmed that StJAZ23 plays a role in drought stress by analyzing several StJAZ23 overexpression (OE-3, OE-5, and OE-6) and RNA interference (RNAi-3, RNAi-6, and RNAi-13) transgenic potato lines. The OE lines displayed significantly increased StJAZ23 expression compared to wild-type (WT) plants, while RNAi lines exhibited significantly reduced expression. The total root length, root tip count, and root surface area were significantly enhanced in OE lines under drought stress, compared to WT plants, whereas RNAi lines showed significant reductions. StJAZ23 overexpression also increased the activities of SOD, POD, CAT, and root vigor under drought stress and JA and ABA hormone levels were also significantly increased in roots under drought stress. These results highlight the positive role of the StJAZ23 gene in enhancing potato resilience to drought stress.

Mutation of ZmDIR5 Reduces Maize Tolerance to Waterlogging, Salinity, and Drought

The DIR (Dirigent) gene family plays a multifaceted role in plant growth, development, and stress responses, making it one of the key gene families for plant adaptation to environmental changes. However, research on ZmDIRs in maize remains limited. In this study, we identified a member of the maize DIR gene family, ZmDIR5, whose promoter region contains numerous elements associated with responses to abiotic stresses. ZmDIR5 is upregulated in response to waterlogging, salt, and drought stresses, and its protein is localized in the endoplasmic reticulum. Subsequent studies revealed that ZmDIR5-EMS (ethyl methane sulfonate) mutant lines exhibited reduced growth compared to WT (wild-type) plants under waterlogging, salt, and drought stress conditions. The mutant lines also demonstrated a relatively higher accumulation of malondialdehyde and reactive oxygen species, lower synthesis of proline and total lignans, and decreased antioxidant enzyme activity under these stress conditions. Additionally, the mutant lines displayed impaired sodium and potassium ion transport capabilities, reduced synthesis of abscisic acid and zeatin, and decreased expression of related genes. The mutation of ZmDIR5 also inhibited the phenylpropanoid biosynthesis pathway in maize. These results indicate that ZmDIR5 serves as a positive regulator of maize tolerance to waterlogging, salt, and drought stresses.

A rapid freezing method to determine tissue layer thickness in drought-stressed leaves

Plants have been affected by water stress ever since they settled on dry land. In severe and persisting drought, plant leaves are wilting. However, a documentation at the anatomical level of the minute changes that occur before wilting is challenging. On the other hand, understanding the anatomical alteration in plant leaves with respect to water stress provides a stronger basis to study molecular and submolecular processes through which plants enhance drought tolerance. In this work, we applied an affordable method to visualise mesophyll layers of Arabidopsis thaliana cell lines without preparation steps that would alter the volume of the cells. We rapidly plunge-froze the leaves in liquid nitrogen, cut them while in the N2 bath, and immediately imaged the mesophyll cross sections in a scanning electron microscope. We applied a reduction of watering from 60 to 40 to 20 mL per day and investigated two time points, 7 and 12 days, respectively. Interestingly, the overall thickness of leaves increased in water stress conditions. Our results showed that the palisade and spongy layers behaved differently under varying watering regimes. Moreover, the results showed that this method can be used to image leaf sections after drought stress without the risk of artefacts or swelling caused by contact to liquids as during chemical fixation.

PLATZ transcription factors and their emerging roles in plant responses to environmental stresses

Plant A/T-rich sequence- and zinc-binding (PLATZ) family proteins represent a novel class of plant-specific transcription factors that bind to A/T-rich sequences. Advances in high-throughput sequencing and bioinformatics analyses have facilitated the identification of numerous PLATZ proteins across various plant species. Over the last decade, accumulating evidence from omics analyses, genetics studies, and gain- and loss-of function investigations has indicated that PLATZ proteins play crucial roles in the complex regulatory networks governing plant development and adaptation to environmental stress. Recently, an excellent review has been published highlighting the roles of PLATZ proteins in controlling plant developmental processes. However, a comprehensive review specifically addressing the molecular mechanisms by which these proteins drive their functions in plant responses to environmental cues is currently lacking. In this review, we summarize the characteristics and identification of PLATZ proteins, emphasizing their significance in stress responses. We also highlight the crosstalk between PLATZ proteins and phytohormones. Furthermore, we discuss the downstream target genes, interacting partners, and upstream regulatory mechanisms associated with PLATZ proteins, providing a thorough understanding of their multifaceted roles in plants.

Diverse roles of MYB transcription factors in plants

MYB transcription factors (TFs), one of the largest TF families in plants, are involved in various plant-specific processes as the central regulators, such as in phenylpropanoid metabolism, cell cycle, formation of root hair and trichome, phytohormones responses, reproductive growth and abiotic or biotic stress responses. Here we summarized multiple roles and explained the molecular mechanisms of MYB TFs in plant development and stress adaptation. The exploration of MYB TFs contributes to a better comprehension of molecular regulation in plant development and environmental adaptability.

The family of glutathione peroxidase proteins and their role against biotic stress in plants: a systematic review

Introduction

Glutathione peroxidases (GPXs) are extensively studied for their indispensable roles in eliminating reactive oxygen species by catalyzing the reduction of hydrogen peroxide or lipid peroxides to prevent cell damage. However, knowledge of GPXs in plants still has many gaps to be filled. Thus, we present the first systematic review (SR) aimed at examining the function of GPXs and their protective role against cell death in plants subjected to biotic stress.

Methods

To guide the SR and avoid bias, a protocol was developed that contained inclusion and exclusion criteria based on PRISMA guidelines. Three databases (PubMed, Science Direct, and Springer) were used to identify relevant studies for this research were selected.

Results

A total of 28 articles related to the proposed objective. The results highlight the importance of GPXs in plant defense against biotic stress, including their role in protecting against cell death, similar to the anti-apoptotic GPXs in animals. Data from gene expression and protein accumulation studies in plants under various biotic stresses reveal that GPXs can both increase resistance and susceptibility to pathogens. In addition to their antioxidant functions, GPXs act as sensors and transmitters of H2O2 signals, integrating with the ABA signaling pathway during stress.

Discussion

These findings show that GPXs delay senescence or reinforce physical barriers, thereby modulating resistance or susceptibility to pathogens. Additionally, their functions are linked to their cellular localization, which demonstrates an evolutionary relationship between the studied isoforms and their role in plant defense. This information broadens the understanding of molecular strategies involving GPX isoforms and provides a foundation for discussions and actions aimed at controlling necrotrophic and/or hemibiotrophic pathogens.

Impact of Nutrient Stress on Plant Disease Resistance

Plants are constantly exposed to abiotic and biotic stresses that seriously affect crop yield and quality. A coordinated regulation of plant responses to combined abiotic/biotic stresses requires crosstalk between signaling pathways initiated by each stressor. Interconnected signaling pathways further finetune plant stress responses and allow the plant to respond to such stresses effectively. The plant nutritional status might influence disease resistance by strengthening or weakening plant immune responses, as well as through modulation of the pathogenicity program in the pathogen. Here, we discuss advances in our understanding of interactions between nutrient stress, deficiency or excess, and immune signaling pathways in the context of current agricultural practices. The introduction of chemical fertilizers and pesticides was a major component of the Green Revolution initiated in the 1960s that greatly boosted crop production. However, the massive application of agrochemicals also has adverse consequences on the environment and animal/human health. Therefore, an in-depth understanding of the connections between stress caused by overfertilization (or low bioavailability of nutrients) and immune responses is a timely and novel field of research with important implications for disease control in crop species. Optimizing nutrient management practices tailored to specific environmental conditions will be crucial in maximizing crop production using environmentally friendly systems.

Stress Increases Ecological Risk of Glufosinate-Resistant Transgene Located on Alien Chromosomes in Hybrids Between Transgenic Brassica napus and Wild Brassica juncea

When glufosinate-resistant transgenic Brassica napus (transgene PAT located on C chromosome) were backcrossed with wild Brassica juncea, 50% of the progeny expressed PAT under favourable conditions. However, exposure to stress (drought, salt, flooding, and intraspecific competition) increased the proportion of plants expressing the PAT gene (r-e plants) by approximately 20% compared to those under unstressed conditions. In the self-pollinated progeny of the stressed plants, the proportion of r-e plants increased by a nearly 30% compared to that of the unstressed plants. Composite fitness was comparable between plants developed under drought stress at the seedling stage and those grown under favourable conditions. Abscisic acid (ABA) content and expression of the Repressor of Silencing 1 (ROS1) in leaves increased significantly after stress treatment in the progeny, with r-e plants exhibiting higher levels. Exogenous ABA treatment significantly up-regulated ROS1 expression in progeny leaves, and the ABA treatment of seeds increased the survival of progeny exposed to glufosinate by 15%. Results suggest that increasing ABA under stress may enhance the demethylation of PAT's promoter by promoting ROS1 expression, thereby inhibiting transgene silencing of PAT, indicating that transgene located on the C chromosome of transgenic B. napus may pose a higher risk of gene flow to wild B. juncea under stress, especially drought stress.

Effects of drought stress on the secondary metabolism of Scutellaria baicalensis Georgi and the function of SbWRKY34 in drought resistance

The pharmacological properties of the dried root of Scutellaria baicalensis Georgi, a Chinese medicinal herb, include antioxidant, antibacterial, and antiviral effects. In S. baicalensis quality assessment, concentrations of baicalin, wogonoside, baicalein, and wogonin in the root are crucial. Drought stress commonly affects the biomass and build-up of active compounds in medicinal sections of medicinal plants and thus their quality. The molecular mechanisms underlying the response of S. baicalensis to drought stress remain unexplored. To delve into the impacts of drought stress on the growth and metabolic processes of S. baicalensis, as well as to unravel the underlying molecular mechanisms. We found prolonged and intensified drought treatment causes an initial surge in its fresh weight, plant height, and stem diameter followed by a gradual slowdown, while malondialdehyde (MDA) content rises; while the fresh weight, length, superoxide dismutase (SOD), and catalase (CAT) activities peak before declining, and the root's diameter continuously narrows. In this study, flavonoid index ingredient levels in S. baicalensis initially decreased, then rose as the drought duration extended, followed by a notable post-rehydration increase in baicalin, wogonoside, and baicalein content and decrease in levels of wogonin and oroxylin A. Transcriptome sequencing and KEGG analysis revealed a significant enrichment of DEGs involved in phenylpropanoid biosynthesis and plant hormone signal transduction pathways. The expression levels of SbPAL, SbCCL, Sb4CL, SbCHI, SbFNSII, SbF6H, and SbUGT genes in the flavonoid biosynthetic pathway and PYR/PYL, PP2C, ABF, and SnRK2 genes in the abscisic acid signal transduction pathway were significantly changed. Drought responsive SbWRKY34 was selected for the subsequent investigation. SbWRKY34 showed the highest level in stems, and the encoding protein was localized in the nucleus. Overexpression of SbWRKY34 in Arabidopsis thaliana (OE-SbWRKY34 lines) resulted in increased sensitivity to drought stress, with considerably reduced MDA content and elevated SOD and CAT activities. Concurrently, the expression levels of AtCAT3, AtDREB, AtRD22, AtRD29A, and AtRD29B were significantly reduced in these lines, suggesting that SbWRKY34 functions to negatively regulate drought resistance in A. thaliana.

Phylogenetic and Expression Analysis of SBP-Box Gene Family to Enhance Environmental Resilience and Productivity in Camellia sinensis cv. Tie-guanyin

Tieguanyin tea, a renowned oolong tea, is one of the ten most famous teas in China. The Squamosa Promoter Binding Protein (SBP)-box transcription factor family, widely present in plants, plays a crucial role in plant development, growth, and stress responses. In this study, we identify and analyze 22 CsSBP genes at the genome-wide level. These genes were distributed unevenly across 11 chromosomes. Using Arabidopsis thaliana and Solanum lycopersicum L. as model organisms, we constructed a phylogenetic tree to classify these genes into six distinct subfamilies. Collinearity analysis revealed 20 homologous gene pairs between AtSBP and CsSBP, 21 pairs between SiSBP and CsSBP, and 14 pairs between OsSBP and CsSBP. Cis-acting element analysis indicated that light-responsive elements were the most abundant among the CsSBP genes. Protein motif, domain, and gene architecture analyses demonstrated that members of the same subgroup shared similar exon-intron structures and motif arrangements. Furthermore, we evaluated the expression profiles of nine CsSBP genes under light, shade, and cold stress using qRT-PCR analysis. Notably, CsSBP1, CsSBP17, and CsSBP19 were significantly upregulated under all three stresses. This study provides fundamental insights into the CsSBP gene family and offers a novel perspective on the mechanisms of SBP transcription factor-mediated stress responses, as well as Tieguanyin tea's adaptation to environmental variations.

Physiological Responses and Metabolic Characteristics of Proso Millet Under Drought Stress During Germination Period

To clarify the impact of drought stress during germination on proso millet's physiological responses and metabolic features, this study used physiological and targeted-like metabolomics methods. With Longmi No. 7 (drought-tolerant, L1) and Longmi No. 15 (drought-sensitive, L2) as materials, we studied the enzyme activities, osmotic adjustment substances, and differential metabolites of proso millet. Results showed that under drought stress, L1's enzyme activities and osmotic adjustment substance contents were significantly higher than L2's, especially at 48-h treatment. 1085 known metabolites were identified from 24 samples, under normal germination, L1's main differential metabolites (amino acids, flavonoids, phytohormone, lipids, sugars, etc.) were enriched in amino acid, lipid, sugar, and energy metabolism pathways. L2's (amino acids, sugars, flavonoids, etc.) were in sugar, lipid metabolism, secondary metabolite biosynthesis, and amino acid metabolism pathways. At 24-h treatment, the metabolic pathways of L1 were mainly concentrated in carbohydrate and nucleotide metabolism, while those of L2 were mainly in carbohydrate and lipid metabolism. At 48 h, the metabolic pathways of L1 were mainly in carbohydrate, energy and lipid metabolism, and those of L2 were mainly in carbohydrate, lipid metabolism, biosynthesis of other secondary metabolites and amino acid metabolism. Under stress, L1's main differential metabolites were organic acids, sugars, flavonoids, amino acids, etc.; L2's were phytohormones, organic acids, sugars, flavonoids, amino acids. This study provides a new direction for the development of proso millet sprouts. Meanwhile, it offers new ideas and theoretical bases for the development of functional foods and the regulation of nutritional components of proso millet.

Crosstalk Between Abiotic and Biotic Stresses Responses and the Role of Chloroplast Retrograde Signaling in the Cross-Tolerance Phenomena in Plants

In the natural environment, plants are simultaneously exposed to multivariable abiotic and biotic stresses. Typical abiotic stresses are changes in temperature, light intensity and quality, water stress (drought, flood), microelements availability, salinity, air pollutants, and others. Biotic stresses are caused by other organisms, such as pathogenic bacteria and viruses or parasites. This review presents the current state-of-the-art knowledge on programmed cell death in the cross-tolerance phenomena and its conditional molecular and physiological regulators, which simultaneously regulate plant acclimation, defense, and developmental responses. It highlights the role of the absorbed energy in excess and its dissipation as heat in the induction of the chloroplast retrograde phytohormonal, electrical, and reactive oxygen species signaling. It also discusses how systemic- and network-acquired acclimation and acquired systemic resistance are mutually regulated and demonstrates the role of non-photochemical quenching and the dissipation of absorbed energy in excess as heat in the cross-tolerance phenomenon. Finally, new evidence that plants evolved one molecular system to regulate cell death, acclimation, and cross-tolerance are presented and discussed.

ABA-mediated regulation of PME12 influences stomatal density, pore aperture, and heat stress response in Arabidopsis thaliana

MAIN CONCLUSION

PME12-mutated plants displayed altered stomatal characteristics and susceptibility to ABA-induced closure. Despite changes in PME activity, the mutant exhibited enhanced thermotolerance. These findings suggest a complex interplay between pectin methylesterification, ABA response, and stomatal function, contributing to plant adaptation to heat stress. Pectin, an essential component of plant cell walls, is synthesized in the Golgi apparatus and deposited into the cell wall in a highly methylesterified form. The degree and distribution of methylesterification within homogalacturonan (HGA) domains are crucial in determining its functional properties. Pectin methylesterase (PME) catalyzes the demethylesterification of HGA, which is pivotal for adjusting cell wall properties in response to environmental cues. Our investigation of PME12, a type-I pectin methylesterase in Arabidopsis, reveals its role in abscisic acid (ABA)-mediated stomatal regulation during heat stress, with the pme12 mutant showing increased stomatal density, reduced size, and heightened sensitivity to ABA-induced closure. Additionally, pme12 plants exhibited altered PME activities under heat stress but displayed enhanced thermotolerance. Moreover, our study identified SCRM as a transcriptional regulator positively influencing PME12 expression, linking stomatal development with PME12-mediated pectin methylesterification. These findings suggest that PME12-mediated pectin modification plays a role in coordinating ABA responses and influencing stomatal behavior under heat stress conditions.

Comprehensive Identification of AREB Gene Family in Populus euphratica Oliv. and Functional Analysis of PeAREB04 in Drought Tolerance

The transcription factors in the ABA Response Element Binding (AREB) protein family were differentially regulated under multiple stress conditions; however, functional analyses of AREB in Populus euphratica Oliv. had not been conducted previously. In the present study, the comprehensive identification of the P. euphratica AREB gene family and the function of PeAREB04 in response to drought stress in P. euphratica were elucidated. A comprehensive analysis of the PeAREB family was first performed, followed by the determination of their expression patterns under drought stress. Bioinformatics analysis revealed that thirteen AREB genes were identified across the P. euphratica genome, with these genes distributed across eight chromosomes in a seemingly random pattern. Phylogenetic analysis indicated that the PeAREB genes could be categorized into four distinct branches. Cis-acting element analysis revealed that most PeAREB genes contained multiple hormone- and stress-responsive elements. Transcriptomic sequencing of P. euphratica seedlings under drought stress showed that most PeAREB genes responded rapidly to drought stress in either the leaves or roots. One gene, PeAREB04, was selected for further functional validation due to its significant upregulation in both leaves and roots under drought stress. Overexpression of PeAREB04 in Arabidopsis thaliana resulted in a high survival rate, reduced water loss in isolated leaves, and a significant reduction in stomatal aperture under natural drought conditions. Drought stress simulations using mannitol further demonstrated that overexpression of PeAREB04 significantly enhanced root elongation. These findings indicate that the identification of the PeAREB gene family and the characterization of PeAREB04's role in drought stress have been largely accomplished. Furthermore, the PeAREB04 gene demonstrates considerable potential as a key target for future genetic engineering strategies aimed at enhancing plant drought resistance.

How the Ectopic Expression of the Barley F-Box Gene HvFBX158 Enhances Drought Resistance in Arabidopsis thaliana

In this study, the drought-responsive gene HvFBX158 from barley was transferred to Arabidopsis thaliana, and overexpression lines were obtained. The phenotypic characteristics of the transgenic plants, along with physiological indicators and transcription level changes of stress-related genes, were determined under drought treatment. Under drought stress, transgenic plants overexpressing HvFBX158 exhibited enhanced drought tolerance and longer root lengths compared to wild-type plants. Additionally, malondialdehyde and hydrogen peroxide contents were significantly lower in transgenic lines, while superoxide dismutase activity was elevated. Quantitative RT-PCR showed that the expression levels of drought and stress response genes, including AtP5CS, AtDREB2A, AtGSH1, AtHSP17.8, and AtSOD, were significantly upregulated. Transcriptome analysis further confirmed that HvFBX158 regulated multiple stress tolerance pathways. In summary, the overexpression of the HvFBX158 gene enhanced drought tolerance in Arabidopsis thaliana by regulating multiple stress response pathways. This study provides a practical basis for improving drought-resistant barley varieties and lays a foundation for subsequent research on F-box family genes for stress resistance in barley.

ZmDnaJ-ZmNCED6 module positively regulates drought tolerance via modulating stomatal closure in maize

Heat Shock Protein plays a vital role in maintaining protein homeostasis and protecting cells from stress stimulation. As one of the HSP40 proteins, DnaJ is a stress response protein widely existing in plant cells. The function and regulatory mechanism of ZmDnaJ, a novel chloroplast-localized type-III HSP40, in maize drought tolerance were characterized. Tissue-specific expression analysis showed that ZmDnaJ is highly expressed in the leaves, and is strongly drought-induced in maize seedlings. Overexpression of ZmDnaJ improved maize drought tolerance by enhancing stomatal closure and increasing ABA content to mediate photosynthesis. In contrast, the CRISPR-Cas9 knockout zmdnaj mutant showed lower relative water content and high sensitivity to drought stress. Moreover, Y2H, BiFC and Co-IP analyses revealed that ZmDnaJ interacts with an ABA synthesis-related protein ZmNCED6 to regulate drought tolerance. Similarly, ZmNCED6 overexpressed lines showed stronger oxidation resistance, enhanced photosynthetic rate, stomatal closure and ABA content, whilst the CRISPR-Cas9 knockout mutant showed sensitive to drought stress. More importantly, ZmDnaJ could regulate key drought tolerance genes (ZmPYL10, ZmPP2C44, ZmEREB65, ZmNCED4, ZmNCED6 and ZmABI5), involved in ABA signal transduction pathways. Taken together, our findings suggest that ZmDnaJ-ZmNCED6 module improves drought tolerance in maize.

Electrochemical sensors for plant signaling molecules

Plant signaling molecules can be divided into plant messenger signaling molecules (such as calcium ions, hydrogen peroxide, Nitric oxide) and plant hormone signaling molecules (such as auxin (mainly indole-3-acetic acid or IAA), salicylic acid, abscisic acid, cytokinin, jasmonic acid or methyl jasmonate, gibberellins, brassinosteroids, strigolactone, and ethylene), which play crucial roles in regulating plant growth and development, and response to the environment. Due to the important roles of the plant signaling molecules in the plants, many methods were developed to detect them. The development of in-situ and real-time detection of plant signaling molecules and field-deployable sensors will be a key breakthrough for botanical research and agricultural technology. Electrochemical methods provide convenient methods for in-situ and real-time detection of plant signaling molecules in plants because of their easy operation, high sensitivity, and high selectivity. This article comprehensively reviews the research on electrochemical detection of plant signaling molecules reported in the past decade, which summarizes the various types electrodes of electrochemical sensors and the applications of multiple nanomaterials to enhance electrode detection selectivity and sensitivity. This review also provides examples to introduce the current research trends in electrochemical detection, and highlights the applicability and innovation of electrochemical sensors such as miniaturization, non-invasive, long-term stability, integration, automation, and intelligence in the future. In all, the electrochemical sensors can realize in-situ, real-time and intelligent acquisition of dynamic changes in plant signaling molecules in plants, which is of great significance for promoting basic research in botany and the development of intelligent agriculture.

Study on molecular response of alfalfa to low temperature stress based on transcriptomic analysis

BACKGROUND

Alfalfa (Medicago sativa L.) is an important high-quality forage crop. Low temperature is an abiotic stress factor that affects the distribution and productivity of alfalfa. To further understand the molecular response to low temperature, and to identify additional genes and metabolic pathways associated with cold tolerance in alfalfa, in this study we conducted transcriptome sequencing, weighted gene co-expression network analysis, KEGG pathway enrichment analysis, and quantitative real-time PCR validation in alfalfa cultivars subjected to low-temperature treatment.

RESULTS

Weighted gene co-expression network analysis revealed that three gene modules were significantly negatively correlated with the semi-lethal temperature for alfalfa. Genes in the three modules were used to construct gene co-expression networks, from which MS.gene46105, MS.gene044087, MS.gene76894, MS.gene44620, MS.gene22005, MS.gene045060, MS.gene31405, and MS.gene74761 were selected as important genes associated with cold tolerance. Quantitative real-time PCR analysis of these eight genes validated the reliability of the transcriptome sequencing data. In addition, further analysis of the genes within the three modules revealed that several transcription factors (AP2/ERF, bZIP, C3H, NAC, and others) and metabolic pathways (N-glycan biosynthesis, citrate cycle, glycolysis/gluconeogenesis, and carbon metabolism, and others) responded well to the low temperature.

CONCLUSIONS

Three gene modules, eight genes, several transcription factors and multiple metabolic pathways associated with cold tolerance were screened. This results will provide a valuable reference for further clarification of the cold tolerance mechanism and breeding for cold tolerance in alfalfa.

MAPKKK28 functions upstream of the MKK1-MPK1 cascade to regulate abscisic acid responses in rice

The mitogen-activated protein kinase (MAPK) cascade (MAPKKK-MAPKK-MAPK) plays a critical role in biotic and abiotic stress responses and abscisic acid (ABA) signalling. A previous study has shown that the ABA-activated MKK1-MPK1 cascade is essential in regulating ABA response and stress tolerance in rice. However, the specific MAPKKK upstream of the MKK1-MPK1 cascade in ABA signalling remains unknown. Here, we identified that MAPKKK28, a previously uncharacterized member of the rice MEKK family, is involved in regulating ABA responses, including seed germination, root growth, stomatal closure, and the tolerance to oxidative stress and osmotic stress. We found that MAPKKK28 directly interacts with and phosphorylates MKK1. Further analysis indicated that the activation of both MKK1 and MPK1 depends on MAPKKK28 in ABA signalling. Genetic analysis revealed that MAPKKK28 functions upstream of the MKK1-MPK1 cascade to positively regulate ABA responses and enhance tolerance to oxidative and osmotic stress. These results not only reveal a new complete MAPK cascade in plants but also uncover its importance in ABA signalling.

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

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

Establishment and Validation of an Efficient Agrobacterium Tumefaciens-Mediated Transient Transformation System for Salix Psammophila

Salix psammophila, C. Wang & Chang Y. Yang, a desert-adapted shrub, is recognized for its exceptional drought tolerance and plays a vital role in ecosystem maintenance. However, research on S. psammophila has been limited due to the lack of an efficient and reliable genetic transformation method, including gene functional studies. The Agrobacterium-mediated transient overexpression assay is a rapid and powerful tool for analyzing gene function in plant vivo. In this study, tissue culture seedlings of S. psammophila were utilized as the recipient materials, and the plant expression vector pCAMBIA1301, containing the GUS reporter gene, was transferred into the seedlings via an Agrobacterium-mediated method. To enhance the efficiency of the system, the effects of secondary culture time, Agrobacterium concentration, infection time, and co-culture duration on the transient transformation efficiency of S. psammophila were explored. The optimal combination for the instantaneous transformation of S. psammophila tissue culture seedlings mediated by Agrobacterium was determined as follows: a secondary culture time of 30 d, a value of OD600 of 0.8, an infection time of 3 h, and a co-culture duration of 48 h. Subsequently, the effectiveness of the transformation system was validated using the S. psammophila drought response gene SpPP2C80. To further confirm the accuracy of the system, SpPP2C80-overexpressing Arabidopsis was constructed and drought resistance analysis was performed. The results were consistent with the transient overexpression of SpPP2C80 in S. psammophila tissue culture seedlings, indicating that this system can be effectively employed for studying gene function in S. psammophila. These findings provide essential information for investigating gene function in non-model plants and pave the way for advancements in molecular biology research in S. psammophila.

The knockout of SlMTC impacts tomato seed size and reduces resistance to salt stress in tomato

Members of the MT-A70 family are key catalytic proteins involved in m6A methylation modifications in plants. They play diverse roles at the posttranscriptional level by regulating RNA secondary structure, selective splicing, stability, and translational efficiency, which collectively affect plant growth, development, and stress responses. In this study, we explored the function of the gene SlMTC, a Class C member of the MT-A70 family, in tomatoes by using CRISPR/Cas9 technology. Compared with the wild-type (WT), the CR-slmtc mutants exhibited decreased seed size and slower growth rates during the seedling stage, along with weaker salt tolerance and significant downregulation of stress-related genes, such as PR1, PR5, and P5CS. The qRT-PCR results revealed that the expression levels of genes involved in auxin biosynthesis (FZY1, FZY3, and FZY4) and polar transport (PIN1, PIN4, and PIN8) were lower in CR-slmtc plants than in the WT plants. In addition, yeast two-hybrid assays showed that SlMTC could interact with SlMTA, a Class A member of the MT-A70 family, providing insights into the potential mode of action of SlMTC in tomatoes. Overall, our findings indicate the critical role of SlMTC in plant growth and development as well as in response to salt stress.

VmSpm1: a secretory protein from Valsa mali that targets apple's abscisic acid receptor MdPYL4 to suppress jasmonic acid signaling and enhance infection

Pathogenic fungi such as Valsa mali secrete effector proteins to manipulate host defenses and facilitate infection. Subtilases are identified as potential virulence factors, yet their specific roles in fruit tree pathogens, such as those affecting apple trees, are poorly understood. Our research shows VmSpm1 as a virulence factor in V. mali. Knocking it out decreased virulence, whereas its heterologous expression in apple led to reduced disease resistance. Using Y2H, BiFC, SLC, and Co-IP techniques, we demonstrated an interaction between VmSpm1 and MdPYL4. MdPYL4 levels increased during V. mali infection. The stable transgenic apple lines inoculation experiment showed that MdPYL4 correlates with enhanced resistance to Apple Valsa canker when overexpressed in apples. Furthermore, through in vitro and in vivo assays, we showed the degradative role of VmSpm1 on MdPYL4. MdPYL4 promotes the synthesis of jasmonic acid (JA) in apples in an abscisic acid-dependent manner. The degradation of MdPYL4 leads to a reduction in JA content in apples during V. mali infection, thereby impairing JA signal transduction and decreasing disease resistance in apple plants. In summary, this study reveals how V. mali utilizes VmSpm1 to subvert JA signaling, shedding light on fungal manipulation of plant hormones to disrupt immunity.

Genome-wide characterization of pyrabactin resistance 1-like (PYL) family genes revealed AhPYL6 confer the resistance to Ralstonia solanacearum in peanut

Bacterial wilt (BW) caused by Ralstonia solanacearum severely impacts the yield and quality of peanut (Arachis hypogaea L.), a globally cultivated industrial crop. Despite the abscisic acid (ABA) signaling pathway have been identified as key factors in peanut resistance to BW, the molecular mechanism remains unclear. Through systematic identification, it was discovered that the peanut genome contains 18 ABA receptor pyrabactin resistance 1-like (PYL) family genes, which show conservation with other plant species. Among these PYL genes in peanut (referred to as AhPYL), AhPYL6 and AhPYL16 showed significant up-regulation in response to salicylic acid, jasmonic acid, ABA treatments, and R. solanacearum infection. Subsequently, the full-length AhPYL6 was cloned and functionally characterized. The fusion protein AhPYL6-YFP was predominantly expressed in the cytoplasm and nucleus of tobacco leaves, and overexpression of AhPYL6 notably enhanced resistance against R. solanacearum. Expression analysis revealed that the expression levels defense -related genes including NbNPR1, NbPR2, NbPR3, NbHRS203, NbEFE26, and NbNDR1 were significantly up-regulated by the overexpression of AhPYL6, which suggested that AhPYL6 confers the resistance to R. solanacearum through promoting expression of defense -related genes. These findings highlight the potential roles of PYL ABA receptors in the plant defense response to bacterial pathogens.

Systematical characterization of Rab7 gene family in Gossypium and potential functions of GhRab7B3-A gene in drought tolerance

BACKGROUND

Cotton serves as a primary source of natural fibers crucial for the textile industry. However, environmental elements such as drought have posed challenges to cotton cultivation, resulting in adverse impacts on both production and fiber quality. Improving cotton's resilience to drought could mitigate yield losses and foster the expansion of cotton farming. Rab7 protein, widely present in organisms, controls the degradation and recycling of cargo, and has a potential role in biotic and abiotic tolerance. However, comprehensive exploration of the Rab7 gene family in Gossypium remains scarce.

RESULTS

Herein, we identified a total of 10, 10, 20, and 20 Rab7 genes through genome-wide analysis in Gossypium arboreum, Gossypium raimondii, Gossypium hirsutum, and Gossypium barbadense, respectively. Collinearity analysis unveiled the pivotal role of whole genome or segmental duplication events in the expansion of GhRab7s. Study of gene architecture, conserved protein motifs, and domains suggested the conservation of structure and function throughout evolution. Exploration of cis-regulatory elements revealed the responsiveness of GhRab7 genes to abiotic stress, corroborated by transcriptome analysis under diverse environmental stresses. Notably, the greatly induced expression of GhRab7B3-A under drought treatment prompted us to investigate its function through virus-induced gene silencing (VIGS) assays. Silencing GhRab7B3-A led to exacerbated dehydration and wilting compared with the control. Additionally, inhibition of stomatal closure, antioxidant enzyme activities and expression patterns of genes responsive to abiotic stress were observed in GhRab7B3-A silenced plants.

CONCLUSIONS

This study sheds light on Rab7 members in cotton, identifies a gene linked to drought stress, and paves the way for additional investigation of Rab7 genes associated with drought stress tolerance.

Herbivory by Leaf-Cutting Ants: Exploring the Jasmonate Response in Host and Non-Host Plants

Leaf-cutting ants (Formicidae; Atta spp., Acromyrmex spp.) cut off pieces of leaves and other plant tissue and feed it to their symbiotic fungi. As this foraging behavior poses an imminent threat to agriculture, leaf-cutting ants are considered as pests of huge ecologically and economically importance. Consequently, research on leaf-cutting ants focused on their foraging decisions and interactions with their cultivated symbiotic fungi, whereas their effect on the attacked plants, apart from the loss of plant tissue, remains largely unknown. In this study, we investigated the consequences of an attack by leaf-cutting ants and analyzed the plants' defense responses in comparison to chewing caterpillars and mechanical damage. We found that an attack by leaf-cutting ants induces the production of jasmonates in several host and non-host plant species (Arabidopsis thaliana, Vicia faba, Phaseolus lunatus, Tococa quadrialata). Additionally, we showed in the natural host plant lima bean (P. lunatus) that leaf-cutting ant damage immediately leads to the emission of typical herbivory-induced plant volatiles, including green leaf volatiles and terpenoids. Further data exploration revealed clear differences in the defense-related phytohormone profile in plant species of Neotropical and Eurasian origin. Taken together, we show that leaf-cutting ant infestation and their way of clipping the plants' tissues induce jasmonate and jasmonates-mediated responses and do not differ from those to mechanical injury or larval feeding.

Physiological, biochemical, and transcriptomic alterations in Castor (Ricinus communis L.) under polyethylene glycol-induced oxidative stress

BACKGROUND

Castor is an important industrial raw material. Drought-induced oxidative stress leads to slow growth and decreased yields in castor. However, the mechanisms of drought-induced oxidative stress in castor remain unclear. Therefore, in this study, physiological, biochemical, and RNA-seq analyses were conducted on the roots of castor plants under PEG-6000 stress for 3 d and 7 d followed by 4 d of hydration.

RESULTS

The photosynthetic rate of castor leaves was inhibited under PEG-6000 stress for 3 and 7 d. Biochemical analysis of castor roots stressed for 3 d and 7 d, and rehydrated for 4 d revealed that the activities of APX and CAT were highest after only 3 d of stress, whereas the activities of POD, GR, and SOD peaked after 7 d of stress. RNA-seq analysis revealed 2926, 1507, and 111 differentially expressed genes (DEGs) in the roots of castor plants under PEG-6000 stress for 3 d and 7 d and after 4 d of rehydration, respectively. GO analysis of the DEGs indicated significant enrichment in antioxidant activity. Furthermore, KEGG enrichment analysis of the DEGs revealed significantly enriched metabolic pathways, including glutathione metabolism, fatty acid metabolism, and plant hormone signal transduction. WGCNA identified the core genes PP2C39 and GA2ox4 in the navajowhite1 module, which was upregulated under PEG-6000 stress. On the basis of these results, we propose a model for the response to drought-induced oxidative stress in castor.

CONCLUSIONS

This study provides valuable antioxidant gene resources, deepening our understanding of antioxidant regulation and paving the way for further molecular breeding of castor plants.

A review on ubiquitin ligases: Orchestrators of plant resilience in adversity

Ubiquitin- proteasome system (UPS) is universally present in plants and animals, mediating many cellular processes needed for growth and development. Plants constantly defend themselves against endogenous and exogenous stimuli such as hormonal signaling, biotic stresses such as viruses, fungi, nematodes, and abiotic stresses like drought, heat, and salinity by developing complex regulatory mechanisms. Ubiquitination is a regulatory mechanism involving selective elimination and stabilization of regulatory proteins through the UPS system where E3 ligases play a central role; they can bind to the targets in a substrate-specific manner, followed by poly-ubiquitylation, and subsequent protein degradation by 26 S proteasome. Increasing evidence suggests different types of E3 ligases play important roles in plant development and stress adaptation. Herein, we summarize recent advances in understanding the regulatory roles of different E3 ligases and primarily focus on protein ubiquitination in plant-environment interactions. It also highlights the diversity and complexity of these metabolic pathways that enable plant to survive under challenging conditions. This reader-friendly review provides a comprehensive overview of E3 ligases and their substrates associated with abiotic and biotic stresses that could be utilized for future crop improvement.

Integrated miRNA and mRNA Transcriptome Analysis Reveals Regulatory Mechanisms in the Response of Winter Brassica rapa to Drought Stress

Drought is a major abiotic stress factor that reduces agricultural productivity. Understanding the molecular regulatory network of drought response in winter rape is of great significance for molecular Brassica rapa. In order to comprehensively analyze the network expression of DEGs and DEMIs in winter rape under drought stress, in this study we used Longyou 7 as the experimental material to identify DEGs and DEMIs related to drought stress by transcriptome and miRNA sequencing. A total of 14-15 key differential mRNA genes related to drought stress and biological stress were screened out under different treatments in the three groups. and 32 differential miRNAs were identified through targeted regulatory relationships, and the mRNA expression of 20 target genes was negatively regulated by the targeting regulatory relationship. It is mainly enriched in starch and sucrose metabolism, carbon metabolism and other pathways. Among them, gra-MIR8731-p3_2ss13GA18GA regulated the expression of multiple mRNAs in the three treatments. miRNA is mainly involved in the drought resistance of Chinese cabbage winter rape by regulating the expression of target genes, such as starch and sucrose metabolism, amino acid biosynthesis, and carbon metabolism. These miRNAs and their target genes play an indispensable role in winter rapeseed drought stress tolerance regulation.

Biomimetic Adaptive Building Façade Modeling for Sustainable Urban Freshwater Ecosystems: Integration of Nature's Water-Harvesting Strategy into Sun-Breakers

Urban freshwater ecosystems have many critical functions, such as providing water to all living things and supporting biodiversity. Factors such as water pollution, increased water consumption, habitat loss, climate change, and drought threaten the health of urban freshwater ecosystems. Looking for solutions to these challenges, this article aims to recycle water and return it to its life cycle using a climate-sensitive water collection strategy. The model focuses on the biomimetic method as a basic strategy. In this regard, the concept of water-harvesting has been examined in detail by conducting a deep literature review, including architecture and engineering disciplines. With all these data obtained, a synthesis/integration study was carried out by developing a model proposal based on adaptive building façade elements to solve the water problems experienced in cities. The model proposal, which is directly related to the titles of "Clean Water and Sanitation (SDG 6)" and "Sustainable Cities and Communities (SDG 11)", which are among the Sustainable Development Goals (SDGs), aims to provide different perspectives on the disciplines with its superficial and functional features. In this context, it is anticipated that the article will become an indispensable resource for other researchers working on the subject.

Comparative physiological and transcriptomic analyses reveal genotype specific response to drought stress in Siberian wildrye (Elymus sibiricus)

Siberian wildrye (Elymus sibiricus) is a xero-mesophytic forage grass with high nutritional quality and stress tolerance. Among its numerous germplasm resources, some possess superior drought resistance. In this study, we firstly investigated the physiological differences between the leaves of drought-tolerant (DT) and drought-sensitive (DS) genotypes under different field water contents (FWC) in soil culture. The results showed that, under drought stress, DT maintained a lower leaf water potential for water absorption, sustained higher photosynthetic efficiency, and reduced oxidative damage in leaves by efficiently maintaining the ascorbic acid-glutathione (ASA-GSH) cycle to scavenge reactive oxygen species (ROS) compared to DS. Secondly, using RNA sequencing (RNA-seq), we analyzed the gene expression profiles of DT and DS leaves under osmotic stress of hydroponics induced by PEG-6000. Through differential analysis, we identified 1226 candidate unigenes, from which we subsequently screened out 115/212 differentially expressed genes (DEGs) that were more quickly induced/reduced in DT than in DS under osmotic stress. Among them, Unigene0005863 (EsSnRK2), Unigene0053902 (EsLRK10) and Unigene0031985 (EsCIPK5) may be involved in stomatal closure induced by abscisic acid (ABA) signaling pathway. Unigene0047636 (EsCER1) may positively regulates the synthesis of very-long-chain (VLC) alkanes in cuticular wax biosynthesis, influencing plant responses to abiotic stresses. Finally, the contents of wax and cutin were measured by GC-MS under osmotic stress of hydroponics induced by PEG-6000. Corresponding to RNA-seq, contents of wax monomers, especially alkanes and alcohols, showed significant induction by osmotic stress in DT but not in DS. It is suggested that limiting stomatal and cuticle transpiration under drought stress to maintain higher photosynthetic efficiency and water use efficiency (WUE) is one of the critical mechanisms that confer stronger drought resistance to DT. This study provides some insights into the molecular mechanisms underlying drought tolerance in E. sibiricus. The identified genes may provide a foundation for the selection and breeding of drought-tolerant crops.

Overexpression of OsRbohH Enhances Heat and Drought Tolerance through ROS Homeostasis and ABA Mediated Pathways in Rice (Oryza sativa L.)

Respiratory burst oxidase homologs (Rbohs) are the primary producers of reactive oxygen species (ROS), which have been demonstrated to play critical roles in plant responses to abiotic stress. Here, we explored the function of OsRbohH in heat and drought stress tolerance by generating overexpression lines (OsRbohH-OE). OsRbohH was highly induced by various abiotic stress and hormone treatments. Compared to wild-type (WT) controls, OsRbohH-OE plants exhibited enhanced tolerance to heat and drought, as determined by survival rate analyses and total chlorophyll content. Histochemical staining revealed that OsRbohH-OE accumulated less ROS. This is consistent with the observed increase in catalase (CAT) and peroxidase (POD) activities, as well as a reduced electrolyte leakage rate and malondialdehyde (MDA) content. Moreover, OsRbohH-OE exhibited enhanced sensitivity to exogenous abscisic acid (ABA), accompanied by altered expression levels of ABA synthesis and catabolic genes. Further analysis indicated that transgenic lines had lower transcripts of ABA signaling-related genes (OsDREB2A, OsLEA3, OsbZIP66, and OsbZIP72) under heat but higher levels under drought than WT. In conclusion, these results suggest that OsRbohH is a positive regulator of heat and drought tolerance in rice, which is probably performed through OsRbohH-mediated ROS homeostasis and ABA signaling.

Dissociation of transcription factor MYB94 and histone deacetylases HDA907/908 alleviates oxidative damage in poplar

Drought is one of the major threats to forest productivity. Oxidation stress is common in drought-stressed plants, and plants need to maintain normal life activities through complex reactive oxygen scavenging mechanisms. However, the molecular links between epigenetics, oxidation stress, and drought in poplar (Populus) remain poorly understood. Here, we found that Populus plants overexpressing PtrMYB94, which encodes an R2R3-MYB transcription factor that regulates the abscisic acid signaling pathway, displayed increased tolerance to extreme drought stress via upregulation of embryogenic cell phosphoprotein 44 (PtrECPP44) expression. Further investigation revealed that PtrMYB94 could recruit the histone deacetylases PtrHDA907/908 to the promoter of PtrECPP44 and decrease acetylation at lysine residues 9, 14, and 27 of histone H3, leading to relatively low transcriptional expression levels under normal conditions. Drought induced the expression of PtrMYB94 while preventing interaction of PtrMYB94 with PtrHDA907/908, which relaxed the chromatin structure and facilitated the binding of RNA polymerase II to the PtrECPP44 promoter. The upregulation of PtrECPP44 helped poplar alleviate oxidative damage and maintain normal cell activities. This study establishes a PtrMYB94-PtrECPP44 transcriptional regulatory module modified by PtrHDA907/908 in modulating drought-induced oxidative stress recovery. Therefore, our study reveals an oxidative regulatory mechanism in response to drought stress and provides insights into molecular breeding for stress resistance in poplar.

Multifaceted role and regulation of aquaporins for efficient stomatal movements

Stomata are micropores on the leaf epidermis that allow carbon dioxide (CO2) uptake for photosynthesis at the expense of water loss through transpiration. Stomata coordinate the plant gas exchange of carbon and water with the atmosphere through their opening and closing dynamics. In the context of global climate change, it is essential to better understand the mechanism of stomatal movements under different environmental stimuli. Aquaporins (AQPs) are considered important regulators of stomatal movements by contributing to membrane diffusion of water, CO2 and hydrogen peroxide. This review compiles the most recent findings and discusses future directions to update our knowledge of the role of AQPs in stomatal movements. After highlighting the role of subsidiary cells (SCs), which contribute to the high water use efficiency of grass stomata, we explore the expression of AQP genes in guard cells and SCs. We then focus on the cellular regulation of AQP activity at the protein level in stomata. After introducing their post-translational modifications, we detail their trafficking as well as their physical interaction with various partners that regulate AQP subcellular dynamics towards and within specific regions of the cell membranes, such as microdomains and membrane contact sites.

Regional differences in leaf evolution facilitate photosynthesis following severe drought

Characterizing physiological and anatomical changes that underlie rapid evolution following climatic perturbation can broaden our understanding of how climate change is affecting biodiversity. It can also provide evidence of cryptic adaptation despite stasis at higher levels of biological organization. Here, we compared evolutionary changes in populations of Mimulus cardinalis from historically different climates in the north and south of the species' range following an exceptional drought. We grew seeds produced from predrought ancestral plants alongside peak-drought descendants in a common glasshouse and exposed them to wet and dry conditions. Before the drought, northern ancestral populations expressed traits contributing to drought escape, while southern ancestral populations expressed drought avoidance. Following the drought, both regions evolved to reduce water loss and maintain photosynthesis in dry treatments (drought avoidance), but via different anatomical alterations in stomata, trichomes, and palisade mesophyll. Additionally, southern populations lost the ability to take advantage of wet conditions. These results reveal rapid evolution towards drought avoidance at an anatomical level following an exceptional drought, but suggest that differences in the mechanisms between regions incur different trade-offs. This sheds light on the importance of characterizing underlying mechanisms for downstream life-history and macromorphological traits.

Functional Identification of MhPYL4 Involved in Iron-Deficiency Stress in Malus Halliana Koehne

The PYL protein family are crucial sensors of the core signals of abscisic acid (ABA) and significantly influence the plant's response to ABA-mediated abiotic stresses as well as its growth and development. However, research on the role of the MhPYL4 gene in iron (Fe) deficiency in apple trees is limited. Studies have shown that the MhPYL4 gene, when exposed to Fe-deficiency stress, exhibits more rapid transcriptional upregulation than other genes' quickly elevated transcription. However, the precise mechanism by which it alleviates this stress remains unclear. The MhPYL4 gene (ID:103432868), isolated from Malus halliana, was analyzed to elucidate its function. Arabidopsis plants engineered to overexpress the MhPYL4 gene exhibited increased leaf chlorosis and slower growth in response to Fe stress compared to the unmodified controls. The transgenic plants also exhibited elevated levels of superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT) activities, as well as ferric chelate reductase (FCR) activities. Levels of malondialdehyde (MDA), hydrogen peroxide (H2O2), and superoxide anion (O2-) were increased. In addition, these transgenic plants had lower concentrations of proline (Pro) and Fe2+, which indicated that their stress tolerance was reduced. Similarly, the overexpression of MhPYL4 in apple calli resulted in inhibited growth and increased susceptibility under Fe stress conditions. Physiological evaluations indicated that the overexpression of MhPYL4 in Arabidopsis reduced its Fe stress tolerance by inhibiting chlorophyll synthesis. In apple calli, it altered pH levels, antioxidant enzyme activity, and Fe-reducing capabilities under the same stress conditions. In summary, the elevated expression of the MhPYL4 gene reduced the tolerance of both Arabidopsis and apple calli to Fe stress, suggesting that MhPYL4 acts as a negative regulator in response to Fe deficiency.

Microbial Fertilizers: A Study on the Current Scenario of Brazilian Inoculants and Future Perspectives

The increasing need for sustainable agricultural practices, combined with the demand for enhanced crop productivity, has led to a growing interest in utilizing microorganisms for biocontrol of diseases and pests, as well as for growth promotion. In Brazilian agriculture, the use of plant growth-promoting rhizobacteria (PGPR) and plant growth-promoting fungi (PGPF) has become increasingly prevalent, with a corresponding rise in the number of registered microbial inoculants each year. PGPR and PGPF occupy diverse niches within the rhizosphere, playing a crucial role in soil nutrient cycling and influencing a wide range of plant physiological processes. This review examines the primary mechanisms employed by these microbial agents to promote growth, as well as the strategy of co-inoculation to enhance product efficacy. Furthermore, we provide a comprehensive analysis of the microbial inoculants currently available in Brazil, detailing the microorganisms accessible for major crops, and discuss the market's prospects for the research and development of novel products in light of current challenges faced in the coming years.