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Abiotic stress impairs plant growth and development, thereby causing low yield and inferior quality of crops. Increasing studies reported that strigolactones (SL) are plant hormones that enhance plant stress resistance by regulating plant physiological processes and gene expressions. In this review, we introduce the response and regulatory role of SL in salt, drought, light, heat, cold and cadmium stresses in plants. This review also discusses how SL alleviate the damage of abiotic stress in plants, furthermore, introducing the mechanisms of SL enhancing plant stress resistance at the genetic level. Under abiotic stress, the exogenous SL analog GR24 can induce the biosynthesis of SL in plants, and endogenous SL can alleviate the damage caused by abiotic stress. SL enhanced the stress resistance of plants by protecting photosynthesis, enhancing the antioxidant capacity of plants and promoting the symbiosis between plants and arbuscular mycorrhiza (AM). SL interact with abscisic acid (ABA), salicylic acid (SA), auxin, cytokinin (CK), jasmonic acid (JA), hydrogen peroxide (H2O2) and other signal molecules to jointly regulate plant stress resistance. Lastly, both the importance of SL and their challenges for future work are outlined in order to further elucidate the specific mechanisms underlying the roles of SL in plant responses to abiotic stress. [ABSTRACT FROM AUTHOR]

Background: Drought is thought to be a major abiotic stress that dramatically limits tomato growth and production. As signal molecule, melatonin (MT) and carbon monoxide (CO) can enhance plant stress resistance. However, the effect and underlying mechanism of CO involving MT-mediated drought resistance in seedling growth remains unknown. In this study, tomato (Solanum lycopersicum L. 'Micro-Tom') seedlings were used to investigate the interaction and mechanism of MT and CO in response to drought stress. Results: The growth of tomato seedlings was inhibited significantly under drought stress. Exogenous MT or CO mitigated the drought-induced impairment in a dose-dependent manner, with the greatest efficiency provided by 100 and 500 µM, respectively. But application of hemoglobin (Hb, a CO scavenger) restrained the positive effects of MT on the growth of tomato seedlings under drought stress. MT and CO treatment promoted chlorophyll a (Chl a) and chlorophyll a (Chl b) accumulations. Under drought stress, the intermediate products of chlorophyll biosynthesis such as protoporphyrin IX (Proto IX), Mg-protoporphyrin IX (Mg-Proto IX), potochlorophyllide (Pchlide) and heme were increased by MT or CO, but uroporphyrinogen III (Uro III) content decreased in MT-treated or CO-treated tomato seedlings. Meanwhile, MT or CO up-regulated the expression of chlorophyll and heme synthetic-related genes SlUROD, SlPPOX, SlMGMT, SlFECH, SlPOR, SlChlS, and SlCAO. However, the effects of MT on chlorophyll biosynthesis were almost reversed by Hb. Conclusion: The results suggested that MT and CO can alleviate drought stress and facilitate the synthesis of Chl and heme in tomato seedlings. CO played an essential role in MT-enhanced drought resistance via facilitating chlorophyll biosynthesis pathway. [ABSTRACT FROM AUTHOR]

In order to survive in extreme environments, plants have evolved multiple mechanisms, such as DNA methylation, to adapt to environmental stress. A large number of investigations indicate that abiotic stress triggers changes in DNA methylation, resulting in fluctuations of expression levels of stress-related genes, thereby enhancing stress tolerance in plants. This review summarized that DNA methylation in plants can enhance tolerance to abiotic stress, including nutrient, sulfur dioxide (SO 2), metal, temperature and osmotic stress. The dynamics of DNA methylation in plant under abiotic stress was discussed from the aspects of genome stability, gene expression, gene silencing and protein interaction. Moreover, several important pathways of methylation also are involved in response to stress. Firstly, methylation activated or inhibited gene expression and mediatted interaction of genes under abiotic stress. Secondly, the RNA-directed DNA methylation (RdDM) pathway can participate in gene expression. Third, up-regulation of DNA methylase and demethylase genes can also affect DNA methylation levels. Fourth, methylation mediated the response of plant antioxidant system. Fifth, DNA methylation had a potential regulatory role in plant cross-adaptation. Additionally, we summarized the methylation of abscisic acid and ethylene synthesis related-genes under stress. We also speculate that the interaction of methylation with other phytohormones can enhance plant stress resistance. Therefore, this review provides a better understanding of plant response to abiotic stress at the molecular level. • DNA methylation in plants can enhance tolerance to nutrient, sulfur dioxide, Aluminum, temperature and osmotic stress. [ABSTRACT FROM AUTHOR]