Transcriptome analysis of genes associated with some phytohormones and phytohormone-like activities in drought-stressed-tomato cultivar super strain B

Phytohormones are crucial signaling mediators that, in trace amounts, modify growth and development-related genes in plants, enhancing their resilience to stress. In the present study, temporally expressed genes of the hormone synthesis pathways for salicylic acid (SA), abscisic acid (ABA), ethylene (ET), and jasmonic acid (JA) were studied in tomato super strain B under drought stress. This cultivar is widely cultivated in Saudi Arabia, so it is a suitable model for studying this stress. Their expressions were analyzed every 2-h interval over a 48-h period. Our findings revealed that the expression pattern of ABA-related genes was more responsive to drought stress than those of ET, SA, and JA. The stomatal-related genes were sensitive to drought stress, whereas probable protein phosphatase 2C_24 and protein phosphatase 2C_53 genes were downregulated during light exposure. In contrast, the serine/threonine-protein kinase gene was upregulated during high light intensity, demonstrating how they influence stomatal reflexes to preserve water. In addition, the guard cell S-type anion channel SLAC1 gene was found to have significantly fluctuated in monitoring the ion channel responsible for drought-induced stomatal closure. The study further revealed a distinct circadian gene expression pattern of the late elongated hypocotyl (LHY) transcription factor family that was upregulated from midnight to midday and then suppressed in the afternoon and the evening, demonstrating how stress reactions and circadian cycles interact to control hormonal pathways. In conclusion, the temporal gene expression dynamics of key hormones under drought stress provide insights into developing drought-resistant tomato varieties and improving stress management strategies.