Decreased low-light regulates plant morphogenesis through the manipulation of hormone biosynthesis in Solanum lycopersicum

Low light intensity limits the growth and development of plants. How plant morphogenesis and adaptation are generated in response to reduced low-light are important for tomato plants. To investigate the light-dependent and long-term adapted regulations on tomato plants, four simulations of gradually reduced light intensity (LI), referred to as 100 % LI, 80 % LI, 67 % LI, and 40 % LI, are designed and performed in four-week-old tomato plants for two more weeks. We find that plant biomass was decreased in response to the reduced light intensity. Interestingly, the stem diameters, internode lengths, light- and CO2- response curves, maximum velocity of RuBP carboxylation by Rubisco (Vcmax), and the maximum potential rate of electron transport contributing to RuBP regeneration (Jmax) are largely affected in 40 % LI, but slightly changed in 80 % LI treatments when compared to 100 % LI control, suggesting moderately decreasing the light intensity did not substantially influence the growth and morphological phenotypes of tomato plants. The mRNA-seq results indicate that the differentially expressed genes (DEGs) are mainly enriched in the pathways corresponding to signal transductions and biosynthesis of plant hormone. We further find that the contents of jasmonic acid (JA), salicylic acid (SA) and zeatin (ZT) are significantly decreased, while content of aminocyclopropane-1-carboxylic acid (ACC) are increased in the plants treated with decreased and low light. Our results present a hypothesis that ZT functions in the regulating the plant stem diameter and internode length in decreased low-light treatments. Our study indicates that multiple plant hormones direct the morphogenesis and adaption in tomato plants in response to reduced low-light environment by manipulation of hormone biosynthesis. Hence, this study updates the understanding of formation of plant morphogenesis and regulation of endogenous hormones in the long-term adapted plants grown under decreased low-light environmental condition.