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The role of melatonin in plant growth and response to environmental stress has been widely demonstrated. However, the physiological and molecular regulation of salt tolerance in wheat seedlings by melatonin remains unclear. In this study, we investigated changes in phenotype, physiology, photosynthetic parameters, and transcript levels in wheat seedlings to reveal the role of melatonin in the regulation of salt tolerance in wheat. The results indicate that the application of exogenous melatonin significantly alleviates growth inhibition, reactive oxygen species accumulation, and membrane oxidative damage induced by salt stress in wheat. Additionally, exogenous melatonin increased antioxidant enzyme activity and regulated photosynthetic gas exchange. Transcriptomic data showed a significant up-regulation of genes encoding light-harvesting chlorophyll protein complex proteins in photosynthesis and genes related to chlorophyll and carotenoid biosynthesis under the influence of melatonin. These results suggest that exogenous melatonin improves salt tolerance in wheat seedlings by enhancing the antioxidant, photoprotective, and photosynthesis activities. [ABSTRACT FROM AUTHOR]

Soil salinity is one of the most critical factors limiting plant growth and development. Carex leucochlora is an important turfgrass species with a wide distribution in northern China that is highly sensitive to salt stress, which impairs its development. Recently, melatonin has emerged as a nontoxic biomolecule that regulates growth and enhances salt tolerance in plants. In this study, the mechanism of melatonin's regulation of plant growth and anatomical characteristics in C. leucochlora seedlings under continuous salt stress was explored. Our results indicated that salt stress strongly suppressed plant growth and leaf cell activity, inhibited root morphology and root activity, and negatively affected leaf and root anatomic structures in the seedlings. Conversely, melatonin (150 μmol L−1) pretreatment improved the detrimental effect of salt stress by restoring the morphology of the leaf, alleviating damage to the cell membrane, improving root activity, and altering the root architecture and plant growth attributes. Moreover, after 12 days of salt stress, anatomical observations of the leaf showed that the thickness of the leaf blade, vascular bundle area of the leaf main vein, vesicular cell area, thickness of the upper epidermis, and thickness of the lower epidermis were increased by 30.55, 15.63, 12.60, 16.76 and 27.53%, respectively, with melatonin under salinity. Melatonin treatment also showed an increase of 5.91, 7.59, 15.57, and 20.51% in epidermal thickness, vascular cylinder diameter, xylem vessel diameter, and pith cell diameter, respectively, compared with salt stress after 12 days. These results suggest that melatonin alleviated salt stress through augmenting seedling growth, leaf cell activity, and root characteristics, maintained the stability of anatomic traits to maintain chloroplast cell homeostasis, and also protected the vascular tissues to promote the radial transport of water and ions in the C. leucochlora seedlings. These modifications induced by the exogenous application of melatonin may help C. leucochlora to acclimate successfully to saline soils. [ABSTRACT FROM AUTHOR]

Low temperature is an important environmental factor limiting the widespread planting of tropical and subtropical crops. The application of plant regulator coronatine, which is an analog of Jasmonic acid (JA), is an effective approach to enhancing crop's resistance to chilling stress and other abiotic stresses. However, the function and mechanism of coronatine in promoting chilling resistance of tomato is unknown. In this study, coronatine treatment was demonstrated to significantly increase tomato chilling tolerance. Coronatine increases H3K4me3 modifications to make greater chromatin accessibility in multiple chilling-activated genes. Corresponding to that, the expression of CBFs, other chilling-responsive transcription factor (TF) genes, and JA-responsive genes is significantly induced by coronatine to trigger an extensive transcriptional reprogramming, thus resulting in a comprehensive chilling adaptation. These results indicate that coronatine enhances the chilling tolerance of tomato plants by inducing epigenetic adaptations and transcriptional reprogramming. [ABSTRACT FROM AUTHOR]

Melatonin (MT) can effectively reduce oxidative damage induced by abiotic stresses such as salt in plants. However, the effects of MT on physiological responses and molecular regulation during wheat germination remains largely elusive. In this study, the response of wheat seeds to MT under salt stress during germination was investigated at physiological and transcriptome levels. Our results revealed that application of MT significantly reduced the negative influence of salt stress on wheat seed germination. The oxidative load was reduced by inducing high activities of antioxidant enzymes. In parallel, the content of gibberellin A3 (GA3) and jasmonic acid (JA) increased in MT-treated seedling. RNA-seq analysis demonstrated that MT alters oxidoreductase activity and phytohormone-dependent signal transduction pathways under salt stress. Weighted correlation network analysis (WGCNA) revealed that MT participates in enhanced energy metabolism and protected seeds via maintained cell morphology under salt stress during wheat seed germination. Our findings provide a conceptual basis of the MT-mediated regulatory mechanism in plant adaptation to salt stress, and identify the potential candidate genes for salt-tolerant wheat molecular breeding. [ABSTRACT FROM AUTHOR]

Summary: The timing of plant organ abscission is modulated by the balance of two hormones, ethylene and auxin, while the mechanism of organ shedding depends on the loss of middle lamella pectin in the abscission zone (AZ). However, the mechanisms involved in sensing the balance of auxin and ethylene and that affect pectin degradation during abscission are not well understood. In this study, we identified two members of the APETALA2/ethylene‐responsive factor (AP2/ERF) transcription factor family in rose (Rosa hybrida), RhERF1 and RhERF4 which play a role in petal abscission. The expression of RhERF1 and RhERF4 was influenced by ethylene and auxin, respectively. Reduced expression of RhERF1 or RhERF4 was observed to accelerate petal abscission. Global expression analysis and real‐time PCR assays revealed that RhERF1 and RhERF4 modulate the expression of genes encoding pectin‐metabolizing enzymes. A reduction in the abundance of pectin epitopes was detected in the AZs of RhERF1 and RhERF4‐silenced plants by immunofluorescence microscopy analysis. In addition, RhERF1 and RhERF4 were shown to bind to the promoter of the pectin‐metabolizing gene β‐GALACTOSIDASE 1 (RhBGLA1), and reduced expression of RhBGLA1 delayed petal abscission. We conclude that during petal abscission, RhERF1 and RhERF4 integrate and coordinate ethylene and auxin signals to modulate pectin metabolism, in part by regulating the expression of RhBGLA1. Significance Statement: This study reports a mechanism for sensing the auxin/ethylene balance associated with modulating petal abscission via degradation of pectin. We found that the expression levels of RhERF1 and RhERF4 are influenced by ethylene and auxin, respectively, and that RhERF1 and RhERF4 act together to modulate pectin degradation in the abscission zone by directly regulating the β‐galactosidase gene RhBGLA1. [ABSTRACT FROM AUTHOR]

Bacterial blight, caused by Xanthomonas axonopodis pv. dieffenbachiae (Xad) , is the most destructive disease of anthurium worldwide, and no effective control technique has been developed currently. The comprehensive survey and precise detection of the pathogen is essential for evaluating disease progress and strengthening management to avoid a serious epidemic. In this study, a total of 253 blight-suspected samples of anthurum and other Araceae species were collected across the country, and 166 potential pathogenic bacteria strains were isolated and purified, after combined analysis on the characteristics of morphology, pathogenicity, 16S rDNA sequences and amplicons of Aad-specific SCAR markers. Finally, 93 of which were considered as X. axonopodis pv. dieffenbachiae. In addition, by using a nested-PCR in repeated detections, 17 out of 21 prevalent anthurium cultivars without blight symptom exhibited latent infection even in young leaves. The results indicated that the anthurium bacterial blight distributed commonly in growing areas in China, and most of the commercial cultivars had no strong resistance. The identification of Xad infection (latent) would be beneficial for the disease forecasting and management improving in anthurium production. [ABSTRACT FROM AUTHOR]

Chestnut (Castanea mollissima) is a deciduous tree species with major economic and ecological value that is widely used in the study of floral development in woody plants due its monoecious and out-of-proportion characteristics. Squamosa promoter-binding protein-like (SPL) is a plant-specific transcription factor that plays an important role in floral development. In this study, a total of 18 SPL genes were identified in the chestnut genome, of which 10 SPL genes have complementary regions of CmmiR156. An analysis of the phylogenetic tree of the squamosa promoter-binding protein (SBP) domains of the SPL genes of Arabidopsis thaliana, Populus trichocarpa, and C. mollissima divided these SPL genes into eight groups. The evolutionary relationship between poplar and chestnut in the same group was similar. A structural analysis of the protein-coding regions (CDSs) showed that the domains have the main function of SBP domains and that other domains also play an important role in determining gene function. The expression patterns of CmmiR156 and CmSPLs in different floral organs of chestnut were analyzed by real-time quantitative PCR. Some CmSPLs with similar structural patterns showed similar expression patterns, indicating that the gene structures determine the synergy of the gene functions. The application of gibberellin (GA) and its inhibitor (Paclobutrazol, PP333) to chestnut trees revealed that these exert a significant effect on the number and length of the male and female chestnut flowers. GA treatment significantly increased CmmiR156 expression and thus significantly decreased the expression of its target gene, CmSPL6/CmSPL9/CmSPL16, during floral bud development. This finding indicates that GA might indirectly affect the expression of some of the SPL target genes through miR156. In addition, RNA ligase-mediated rapid amplification of the 5′ cDNA ends (RLM-RACE) experiments revealed that CmmiR156 cleaves CmSPL9 and CmSPL16 at the 10th and 12th bases of the complementary region. These results laid an important foundation for further study of the biological function of CmSPLs in the floral development of C. mollissima. [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]