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Coronatine (COR) is a phytotoxin produced by Pseudomonas syringae and is a functional analogue of the bioactive hormone JA-Ile, which is widely involved in plant defence responses. In this study, we explored the effects of exogenous applications of COR on tobacco plants under polyethylene glycol-induced drought stress. Compared with control (CK), COR-treated tobacco plants exhibited higher leaf relative water content and better photosynthetic performance under drought exposure. Ultrastructural examination revealed that drought led to stomatal closure and disorganization of granum stacking in the chloroplasts (with obvious accumulation of plastoglobuli), and mitochondria in the CK samples presented injured cristae. In the leaf tissue of the COR-treated plants, regularly stacked granum thylakoids, few plastoglobuli and intact mitochondrial membranes and cristae were observed. Totals of 1803 and 6207 differentially expressed genes (DEGs) were identified between the samples from the COR-treated and CK plants under well-watered and drought conditions. Functional annotation analysis revealed that these DEGs were involved mainly in plant hormone signal transduction, cellular carbohydrate metabolic processes and photosynthesis processes. Six hundred forty transcription factor genes were also identified among the DEGs. This study provides a global view of COR-induced drought stress tolerance in tobacco from both physiological and transcriptional aspects. [ABSTRACT FROM AUTHOR]

Drought is a key limiting factor for cotton ( Gossypium spp.) production, as more than half of the global cotton supply is grown in regions with high water shortage. However, the underlying mechanism of the response of cotton to drought stress remains elusive., By combining genome-wide transcriptome profiling and a loss-of-function screen using virus-induced gene silencing, we identified Gossypium hirsutum Gh WRKY59 as an important transcription factor that regulates the drought stress response in cotton., Biochemical and genetic analyses revealed a drought stress-activated mitogen-activated protein ( MAP) kinase cascade consisting of Gh MAP3K15-Mitogen-activated Protein Kinase Kinase 4 (GhMKK4)-Mitogen-activated Protein Kinase 6 (GhMPK6) that directly phosphorylates Gh WRKY59 at residue serine 221. Interestingly, Gh WRKY59 is required for dehydration-induced expression of Gh MAPK3K15, constituting a positive feedback loop of Gh WRKY59-regulated MAP kinase activation in response to drought stress. Moreover, Gh WRKY59 directly binds to the W-boxes of DEHYDRATION-RESPONSIVE ELEMENT-BINDING PROTEIN 2 ( Gh DREB2), which encodes a dehydration-inducible transcription factor regulating the plant hormone abscisic acid ( ABA)-independent drought response., Our study identified a complete MAP kinase cascade that phosphorylates and activates a key WRKY transcription factor, and elucidated a regulatory module, consisting of Gh MAP3K15-Gh MKK4-Gh MPK6-Gh WRKY59 -Gh DREB2, that is involved in controlling the cotton drought response. [ABSTRACT FROM AUTHOR]

The aim of this study was to investigate the effect of silicon (Si) on soybean seedlings under (combined) drought and ultraviolet-B (UV-B) radiation stresses. Specifically, we determined dry matter accumulation and partitioning of the mineral elements in different organs of soybean seedlings using the inductively coupled plasma mass spectrometry (ICP-MS). The amount of dry matter accumulated in root, stem, and leaf of seedlings treated with (combined) drought and UV-B radiation stresses were lower than that of the control. Also, the content of macroelements in seedlings under the combined stress was lower than in those under control conditions. Changes in the contents of microelements varied according to the intensity of drought, UV-B radiation, and the organs of soybean. The relationship between the contents of mineral elements and the accumulation of dry matter also varied similarly. These results demonstrated that drought and UV-B radiation induced an alteration in the distribution of mineral elements in root, stem and leaf, leading to decreases in dry matter accumulation and inhibition of soybean growth. [ABSTRACT FROM PUBLISHER]

Coronatine (COR) is a chlorosis-inducing phytotoxin that mimics some biological activities of methyl jasmonate (MeJA). Although MeJA has been reported to alleviate drought stress, it is unclear if COR has the same ability. Our objective was to determine the influence of exogenously applied MeJA and COR on the growth and metabolism of cauliflower seedlings under drought stress and recovery. Both MeJA and COR enhanced the growth and accumulation of dry matter in cauliflower seedlings during drought-stressed and rewatering conditions. Treatment with MeJA or COR enhanced tolerance of drought stress through increased accumulation of chlorophyll and net photosynthetic rate. Enzymatic (superoxide dismutase, peroxidase, catalase, ascorbate peroxidase, and glutathione reductase) and nonenzymatic antioxidant (proline and soluble sugar) systems were activated, and lipid peroxidant (malondialdehyde and hydrogen peroxide) was suppressed by MeJA and COR under drought stress. MeJA and COR also increased leaf relative water content and endogenous abscisic acid level under drought-stressed conditions. After rewatering, the contents of leaf water, chlorophyll, abscisic acid, and photosynthetic characteristics as well as enzymatic and nonenzymatic antioxidant systems showed nearly complete recovery. Both MeJA and COR can alleviate the adverse effects of drought stress and enhance the ability for water stress resistance through promotion of defense-related metabolism in cauliflower seedlings. [ABSTRACT FROM AUTHOR]

Drought is one of the most common environmental stressors that severely threatens plant growth, development, and productivity. B2 (2,4-dichloroformamide cyclopropane acid), a novel plant growth regulator, plays an essential role in drought adaptation, significantly enhancing the tolerance of Carex breviculmis seedlings. Its beneficial effects include improved ornamental value, sustained chlorophyll content, increased leaf dry weight, elevated relative water content, and enhanced root activity under drought conditions. B2 also directly scavenges hydrogen peroxide and superoxide anion contents while indirectly enhancing the activities of antioxidant enzymes (superoxide dismutase, peroxidase, catalase, and ascorbate peroxidase) to detoxify reactive oxygen species (ROS) oxidative damage. Transcriptome analysis demonstrated that B2 activates drought-responsive transcription factors (AP2/ERF-ERF, WRKY, and mTERF), leading to significant upregulation of genes associated with phenylpropanoid biosynthesis (HCT, POD , and COMT). Additionally, these transcription factors were found to suppress the degradation of starch. B2 regulates phytohormone signaling related-genes, leading to an increase in abscisic acid contents in drought-stressed plants. Collectively, these findings offer new insights into the intricate mechanisms underlying C. breviculmis' resistance to drought damage, highlighting the potential application of B2 for future turfgrass establishment and management with enhanced drought tolerance. • B2 pretreatment alleviates drought-induced damage in Carex breviculmis. • B2 mitigates oxidative stress by detoxifying ROS and reducing oxidative damage. • The crosstalk between B2 and plant hormones in augmenting drought tolerance. • B2 enhances drought resistance by promoting starch accumulation. [ABSTRACT FROM AUTHOR]

Coronatine (COR) is a phytotoxin produced by Pseudomonas syringae . Its structure is similar to those of jasmonates (JAs), which play diverse roles in multiple plant biotic and abiotic defenses. However, the biological activity of COR is 1000 times greater than the activity of JA. In addition to being involved in the JA pathway, COR affects plant photosynthetic efficiency. In this study, we examined wheat blade pretreatment with COR. Blades treated with COR remained green longer than those of control plants under drought stress conditions, resulting in less yield loss with COR treatment. To investigate the mechanism of COR in drought resistance further, we employed two-dimensional gel electrophoresis technology and matrix-assisted laser desorption/ionization mass spectrometry to sequester and identify key proteins. Six COR-inducible proteins that are located in the chloroplast and involved directly in photosynthesis were found. The wheat homologue of protein gi|326509937 is degradation of periplasmic proteins 1 (DEGP1) in Arabidopsis , which is a response to photosystem II reparation, and was maintained at a low level with COR treatment. Finally, we measured levels of chlorophyll and photosynthetic performance to reveal the phenotypic effect of COR. Taken together, the results demonstrate that COR enhances drought tolerance by maintaining high photosynthetic performance. [ABSTRACT FROM AUTHOR]

Plant growth regulators (PGRs) play crucial roles in maize drought tolerance. However, most of the studies are focused on seedling stage under greenhouse conditions, little is known on the effects of grain yields at later growth stage under field environment. It is hypothesized that exogenous application of PGRs can increase maize drought tolerance at different growth stages under field conditions. Here we used alginate oligosaccharide (AOS) and coronatine (COR) to investigate the effects of these two PGRs on maize drought tolerance in a two-year field experiment. The results showed that both COR and AOS treatments reduced leaf water loss and significantly increased the relative leaf water content by 12.6% and 13.0%, thus significantly decreasing superoxide anion accumulation by 49% and 42% in maize seedlings. There was no big difference between these two treatments in the seedling stage. In the subsequent reproductive growth period, although both COR and AOS treatments significantly increased leaf photosynthesis and above-ground growth, including photosynthetic rate by 41% and 33%, relative chlorophyll content (SPAD value) by 8.0% and 6.5%, leaf area by 22% and 15%, plant height by 8.3% and 5.9%, dry matter accumulation by 23% and 17%, respectively, under drought conditions, the effect of COR was superior to the AOS, as evidenced by membership function values of COR treatment were 0.12 and 0.08 larger than that of AOS treatment in 2020 and 2021, respectively. Ultimately, COR and AOS treatments significantly increased the grain yields by 21.7% and 16.2% in 2020, 22.3% and 15.7% in 2021, respectively, under drought conditions. Path analysis showed both PGRs increased final grain yields by increasing thousand-kernel weight (TKW). While the TKW increase with COR treatment was mainly due to the increase of relative chlorophyll content (SPAD value), AOS treatment mainly increased dry matter accumulation under drought conditions. [Display omitted] • Effects of coronatine (COR) and alginate oligosaccharide (AOS) on drought tolerance examined. • Both COR and AOS treatments improved maize drought tolerance. • Treatment of maize seedling contributed to the whole growth period. • The COR treatment was more pronounced in the reproductive growth period. • The COR treatment was superior to that of the AOS treatment. [ABSTRACT FROM AUTHOR]

Drought is an important factor limiting plant growth, development, and productivity. Recently, coronatine (COR) has emerged as a mimic of jasmonates, which play diverse roles in plant tolerance to multiple stressors. Although COR affects the response to drought stress in Carex leucochlora seedlings, the mechanism by which it acts is unclear. We characterized the acclimation of C. leucochlora to drought stress using plant growth, osmotic adjustment, photosynthetic parameters, antioxidant enzyme system and comparative transcriptomics analyses during stress treatments, COR (0.1 nmol L−1) was applied under soil water stress (20 ± 5%) in the growth chamber. Drought stress strongly suppressed biomass accumulation and loss of cellular water content, inhibited photosynthesis, and damaged cellular membranes in the seedlings. Conversely, COR treatment improved the detrimental effects of drought stress by restoring leaf morphology, alleviating damage to the cell membrane, and improving photosynthetic efficiency and water use efficiency. In addition, COR enhanced the activities of superoxide dismutase, peroxidase activity, catalase, and ascorbate peroxidase. There were 1205 transcripts (36.7%) that were common with COR application uniquely induced by drought stress. COR regulated transcription factors from 48 families such as AP2/ERF-ERFs, bHLHs, bZIPs, and C2H2s, and the genes were mainly involved in starch and sucrose metabolism, phenylpropanoid biosynthesis, and plant hormone signal transduction. Taken together, these results provide the physiological mechanism underlying improved drought resistance in C. leucochlora in the presence of COR and provide a new perspective for gene function analysis in COR-mediated signaling pathways. In addition, these findings provide new guidance strategies for the application of COR to improve drought management systems in C. leucochlora establishment and management. • Coronatine improved the drought tolerance of Carex leucochlora seedlings. • Coronatine increased growth, photosynthesis, and antioxidants under drought stress. • Coronatine regulated key gene expression involved in hormone signaling transduction. • A possible molecular mechanism of coronatine in regulating drought was revealed. [ABSTRACT FROM AUTHOR]

Cuticular wax is the outermost thin hydrophobic layer covering the surface of aerial plant parts, which provides a primary waterproof barrier and protection against different environmental stresses. The aim of the present study was to investigate the role of ethephon, as an ethylene-releasing compound, in counteracting drought stress by modulating cuticular wax biosynthesis, water balance, and antioxidant regulation in maize seedlings. Our results showed that ethephon significantly increased the ethylene evolution rate, regulate the expression of cuticular wax synthesis regulatory gene ZmERE and the wax biosynthetic genes ZmGL1 , ZmGL15 , ZmFDH1 , and ZmFAE1 , and promote cuticular wax accumulation in maize seedlings under normal or drought stress conditions. Moreover, ethephon was shown to might markedly reduce water loss and chlorophyll leaching in leaves, and maintain higher relative water content and leaf water potential under drought stress. Ethephon significantly decreased malondialdehyde and hydrogen peroxide concentrations and electrolyte leakage, but increased the accumulation of proline and the activities of SOD, POD, and CAT. In addition, ethephon resulted in an increase in the ratio of root and shoot under drought stress. These results indicated that ethephon could improve maize performance under drought stress by modulating cuticular wax synthesis to maintain water status and membrane stability for plant growth. [ABSTRACT FROM AUTHOR]

Highlights: [•] Coronatine enhanced photosynthesis and 14C translocation under drought stress. [•] Coronatine-treated plants had better membrane stability and water status under drought stress. [•] Coronatine-treated plants exhibited higher antioxidant enzyme activities during drought stress. [•] Coronatine alleviated biomass reduction under drought stress. [Copyright &y& Elsevier]

Abstract: Drought is a major environmental stress factor that affects growth and development of plants. Abscisic acid (ABA), osmotically active compounds, and synthesis of specific proteins, such as proteins that scavenge oxygen radicals, are crucial for plants to adapt to water deficit. LOS5/ABA3 (LOS5) encodes molybdenum-cofactor sulfurase, which is a key regulator of ABA biosynthesis. We overexpressed LOS5 in tobacco using Agrobacterium-mediated transformation. Detached leaves of LOS5-overexpressing seedlings showed lower transpirational water loss than that of nontransgenic seedlings in the same period under normal conditions. When subjected to water-deficit stress, transgenic plants showed less wilting, maintained higher water content and better cellular membrane integrity, accumulated higher quantities of ABA and proline, and exhibited higher activities of antioxidant enzymes, i.e., superoxide dismutase, catalase, peroxidase and ascorbate peroxidase, as compared with control plants. Furthermore, LOS5-overexpressing plants treated with 30% polyethylene glycol showed similar performance in cellular membrane protection, ABA and proline accumulation, and activities of catalase and peroxidase to those under drought stress. Thus, overexpression of LOS5 in transgenic tobacco can enhance drought tolerance. [Copyright &y& Elsevier]