Search

Endogenous melatonin (MEL) and abscisic acid (ABA) are involved in the adaptation of plants to environmental stresses. The application of exogenous serotonin (SER) to plants can enhance their tolerance to abiotic stress, such as cold. However, the mechanism associated with serotonin-mediated defense against cold-induced damage in mangroves is still poorly understood. In this study, we demonstrated that mangrove (Kandelia obovata) seedlings sprayed with 200 μmol·L−1 serotonin exhibited enhanced cold tolerance, as shown by reduced damage to leaves and loss of photosynthesis when exposed to low-temperature conditions. The mechanism associated with the cold adaptation of K. obovata seedlings upon treatment with serotonin was subsequently investigated by transcriptomic analysis. Serotonin treatment caused changes in differentially expressed genes (DEGs) involved in the regulation of melatonin (MEL) and ABA biosynthesis and defense responses against cold stress. Under low-temperature stress, serotonin-treated seedlings showed a significant increase in the endogenous levels of melatonin and ABA. By contrast, under normal growth conditions, K. obovata seedlings treated with serotonin displayed no substantial change in melatonin level, whereas ABA level significantly increased. These findings demonstrated that serotonin treatment might play an important role in the enhanced resistance to cold in K. obovata and that such an effect would depend on the activation of endogenous melatonin and ABA synthesis. [ABSTRACT FROM AUTHOR]

Plant basic helix-loop-helix (bHLH) transcription factors play pivotal roles in responding to stress, including cold and drought. However, it remains unclear how bHLH family genes respond to these stresses in Kandelia obovata. In this study, we identified 75 bHLH members in K. obovata, classified into 11 subfamilies and unevenly distributed across its 18 chromosomes. Collineation analysis revealed that segmental duplication primarily drove the expansion of KobHLH genes. The KobHLH promoters were enriched with elements associated with light response. Through RNA-seq, we identified several cold/drought-associated KobHLH genes. This correlated with decreased net photosynthetic rates (Pn) in the leaves of cold/drought-treated plants. Weighted gene co-expression network analysis (WGCNA) confirmed that 11 KobHLH genes were closely linked to photoinhibition in photosystem II (PS II). Among them, four Phytochrome Interacting Factors (PIFs) involved in chlorophyll metabolism were significantly down-regulated. Subcellular localization showed that KobHLH52 and KobHLH30 were located in the nucleus. Overall, we have comprehensively analyzed the KobHLH family and identified several members associated with photoinhibition under cold or drought stress, which may be helpfulfor further cold/drought-tolerance enhancement and molecular breeding through genetic engineering in K. obovata. [ABSTRACT FROM AUTHOR]