The Influence On Chlorophyll Fluorescence And The Expression Of PsbA Genes Of Chinese Bayberry Under High-temperature And High-light Stress

Chinese bayberry (Myrica rubra Sieb.&Zucc.) is an evergreen subtropic fruit tree originated inChina, which occupied more than99%of the total cultivated area in the world. Photosynthesis is thephysiological basis of bayberry for growth and development, but it is always constrained by adversedexternal environment conditions in summer, such as high-temperature and high-light stress. D1protein(encoded by PsbA genes) as the most important protein subunits of PSII system, its turn-overmechanism under stress conditions will become an important mean of improving plant stress tolerance.Taking cultivars ‘Dongkui’ and ‘Tanmei’ with different resistance to light and heat stress as materials,by measuring their chlorophyll fluorescence parameters and the expression of psbA genes underhigh-temperature and high-light stress to research the effects of its photosynthetic institutions and D1protein turnover in summer. The results will potentially help to screen genetypes resistant to light andheat stresses and develop new techniques to alleviate the damage of light and heat stresses for Chinesebayberry cultivation. The main results of this project are as follows:(1) Compared with25℃+500μmolm-2s-1treatment, two kinds of Chinese bayberry F0increasedobviously, Fv/Fm, ETR, ΦPSII and qP decrease significantly under the condition of40℃+1500μmolm-2s-1, it is indicated that PSII reaction center must damage by high-light andhigh-temperature light can aggravated this photoinhibition.‘Dongkui’ is smaller than ‘Tanmei’indicate that ‘Dongkui’ may more resistant to high-temperature and strong-light than ‘Tanmei’.(2) Study on the reaction of different inhibitors to photosynthetic mechanism under hightemperature of40℃, finding that three kinds of inhibitors were exacerbated by high temperature highlight damage to the PSII reaction centers. And DCMU is the most effective factor to chlorophyllfluorescence of Chinese bayberry.(3) The PsbA gene full-length cDNA sequences was cloned, The amino acid sequence similarity ofarabidopsis, rice, liquidambar cacao trees was99%and it is more than96%of nucleotide.(4) Study on the the expression level of PsbA genes were mainly regulated by light at25℃, buthigher expression level of PsbA genes under low light intensity with35℃and40℃，it is indicated thatillumination of PsbA gene expression regulation are greatly influenced by temperature.‘Dongkui’ wasthe cultivar having significantly higher expression level of the PsbA genes may be important reason for the more resistant to high temperature and strong stress.(5) Compared with25℃+500μmolm-2s-1treatment, the D1protein and Deg1protease were lowerunder the condition of40℃+1500μmolm-2s-1. It is the high temperature and strong light generatedinteraction coupling phenomenon and cause the degradation of capsule membrane proteins. And both inthe high temperature under the strong light of D1protein turnover play an important role.