Roles Of A Caffeic Acid-O-methyltransferase In Regulating Leaf Senescence In Tomato

Tomato(Solanum lycopersicum L.)is the world’s largest vegetable crop.The adverse environment and nutrient limitation in production accelerate plant senescence,resulting in decreased yield and quality.Melatonin(MT)is a tryptamine compound that can be detected in many plant cells.In recent years,more and more studies have shown that the exogenous application of MT and the increase in the level of endogenous MT can lead to Enhance the resistance of plants to various stresses,but the role of SlCOMT1,a gene encoding a key enzyme in MT synthesis,in the process of tomato senescence and its underlying molecular mechanisms are still poorly understood.Related research is very important for improving crop quality and yield.Significance.In this paper,the ’Micro-tom’ tomato was used as the experimental material to study the effect of exogenous MT on the physiological and biochemical indicators of dark-induced tomato senescence.The SlCOMT1 gene was cloned and analyzed by bioinformatics and spatiotemporal expression patterns.The SlCOMT1 gene deletion mutant comt1 was used to study the senescence effects of in vitro and root-restricted cultivation on functional leaves of tomato.The effects of comt1 on flower organ senescence and fruit ripening were analyzed and evaluated.The main findings are as follows:1.Exogenous MT pretreatment delayed dark-induced senescence in tomato functional leaves by up-regulating the metabolic bypass of γ-aminobutyric acid,ascorbic acid biosynthesis,glutathione-ascorbic acid cycle,and transcription of genes related to the antioxidant system.2.The expression patterns of SlCOMT1 in tomato leaves,flower organs and fruits during development and senescence,as well as the changes in endogenous MT content levels,were not the same.3.The expression of SlCOMT1 in isolated tomato leaves was inhibited by dark treatment,while JA treatment highly induced SlCOMT1 expression.4.The senescence-associated gene(SAG)and chlorophyll degradation-related genes of leaves of comt1 mutants cultured in vitro under dark conditions were significantly higher than those of WT.5.The developmental phenotype of the comt1 mutant was not significantly different from that of the WT,while the petal closure time of the comt1 mutant was significantly lower than that of the WT,and its stalk abscission rate was 2.33 times higher than that of the WT.Although there was no significant change in comt1 fruit phenotype,in vitro comt1 fruit showed late-ripening characteristics,indicating that SlCOMT1 gene is also involved in the development of floral organs and the process of fruit ripening and senescence.