Preliminary Analysis On The Mechanism Of Ethephon Alleviating The Chlorosis Of Zoysiagrass(zoysia Japonica Steud.L)at Low Temperature

Zoysiagrass is a native grass species and can be used as turf and forage grass in China.Zoysiagrass has many excellent characteristics.However,when it grows in northern China,its leaves turn yellow too early in late fall,which affects its wider use age.Previous studies have shown that ethephon can alleviate leaf chlorosis and slow down the decrease of chlorophyll content in zoysiagrass under low temperature stress.The underlying mechanism is not clear.In this study,zoysiagrass was used as the experimental material to study the mechanism of ethephon in relieving the leaf chlorosis of zoysiagrass under low temperature stress in three aspects: ethylene synthesis and signal transduction,oxidative bleaching pathway of chlorophyll degradation and PAO pathway of chlorophyll degradation.By detecting the ethylene release rate and chlorophyll content in leaves,the ethylene synthesis,ethylene signal transduction and chlorophyll metabolism pathways were analyzed and compared at gene expression and protein level and main results and conclusions are as following:1.Spraying 150 mg/L ethephon on leaves can effectively alleviate the phenomenon of leaf chlorosis and chlorophyll content degradation of zoysiagrass under low temperature stress.2.Ethephon treatment did not affect the ethylene release rate of zoysiagrass under low temperature stress.Compared with the control,there was no significant difference between ACC content and ethylene release rate and there was no difference in protein expression in ethylene synthesis KEGG enrichment analysis.Ethephon treatment inhibited the gene expression of Zj EIN3-2,Zj EIN3-3 and Zj ERF1/2 in ethylene signal transduction pathway,and inhibited the protein enrichment of EIN3 and ERF1/2.The results indicated that the effect of ethephon on chlorophyll of zoysiagrass under low temperature stress was mainly through inhibiting ethylene signal transduction pathway,but not through affecting ethylene biosynthesis.3.The effect of ethephon treatment on alleviating oxidative stress induced by aging is not obvious,and the activities of antioxidant enzymes and PPO enzymes have no significant changes.The effect of ethephon treatment on chlorophyll oxidative bleaching pathway of zoysiagrass is not significant.4.Ethephon alleviates leaf yellowing of zoysiagrass under low temperature stress mainly through affecting the chlorophyll PAO degradation pathway.Specifically,ethephon treatment inhabited the decrease of light capture protein induced by low temperature stress,inhibited the further significant high expression of Zj MDCase and Zj PPH gene and reduced NYC,MDCase,PAO,RCCR protein concentration in PAO pathway and eventually reduced the rapid degradation of chlorophyll in zoysiagrass and inhibited in Pao pathway and NYC,the up-regulation of PAO and RCCR further slowed down the rapid degradation of zoysiagrass chlorophyll.5.Protein KEGG enrichment analysis indicated that Zj SGR gene was involved in the ethephon mediated inhibition of chlorophyll PAO degradation pathway by ethephon by affecting CHLase and RCCR.