Elucidating the molecular mechanisms of exogenous melatonin for improving heat tolerance in Solanum tuberosum L. seedlings

In the era of climate change, the rise in temperature can adversely impact the potato growth, yield and even threaten food security. Temperature both as high and long-term have always retarded growth and development of potatoes. Based on this, overall study provides experimental proof of potato (Solanum tuberosum L.) heat tolerance mechanisms. Plant hormone melatonin (MT) elicits and improves potato tolerance against high temperature, but scarce information is present about detailed mechanisms. Therefore, introduction of exogenous MT in potato seedlings (Lishu 6) together with high-temperature stress was investigated to find the physiological and molecular mechanisms. Temperature stress results in wilting of basal leaves and inhibits photosynthesis in potato seedlings. Interestingly, we found distinct effects of introduced MT with increase in the actual photosynthetic quantum yield (ΦPSII), apparent photosynthetic electron transport rate (ETR), chlorophyll content, intercellular CO2 concentration (Ci), net photosynthetic rate (Pn), photochemical quenching (qP), and transpiration rate (Tr). Further, hydrogen peroxide (H2O2) content and activities of antioxidant enzymes in potato seedling leaves reduced after introduction of exogenous MT. Through transcriptome analysis, we found that during temperature stress, MT significantly upregulated the expression of genes involved in photosynthesis and antioxidant enzymes, and plant hormone signal transduction. Importantly, it also augmented antioxidant capacity in potato seedlings and alleviated the damage at high temperature. In summary, we provide evidence that identifying factors could modulate the potential interaction of temperature stress with introduced MT to improve the heat tolerance of potato seedlings for maximum function.