Project description:Rhododendron is well known woody plant, as having high ornamental and economic values. Heat stress is one of the important environmental stresses that effects Rhododendron growth. Recently, melatonin was reported to alleviate abiotic stress in plants. However, the role of melatonin in Rhododendron is still unknown. In the present study, the effect of melatonin on Rhododendron under heat stress and the potential mechanism was investigated. Through morphological characterization and chlorophyll a fluorescence analysis, 200µM was selected for the best melatonin concentration to mitigate heat stress in Rhododendron. To reveal the mechanism of melatonin priming alleviating the heat stress, the photosynthesis indexes, Rubisco activity and ATP content were detected in 25 ℃, 35 ℃ and 40 ℃. The results showed that melatonin improves electron transport rate (ETR), PSII and PSI activity, Rubisco activity and ATP content under high temperature stress. Furthermore, transcriptome analysis showed that a significant enrichment of differentially expressed genes in the photosynthesis pathway, and most of genes in photosynthesis pathway displayed a more significantly slight down-regulation under high temperature stress in melatonin-treatment plants, compared with melatonin-free plants. We identified PGR5……Together, these results demonstrate that melatonin could promote the photosynthetic electron transport, improve the enzymes activities in Calvin cycle and the production of ATP, and thereby increase photosynthetic efficiency and CO2 assimilation capacity under heat stress, through regulating the expression of some key genes, such as PGR5…Therefore, melatonin application displayed great potential to cope with the heat stress in Rhododendron.
