Study On The Mechanism Of OsPUP1 In Regulating High Temperature Tolerance In Rice

High temperature stress is one of the main abiotic stresses that affect the yield of rice.It is of great theoretical and realistic significance to clone genes regulating high temperature tolerance of rice and reveal its regulatory mechanisms for high temperature tolerance breeding.Cytokinins are plant hormones that play important roles in cell division,leaf senescence and abiotic stresses response.Rice purine permease（PUP）is considered to be a class of protein with functions in transporting cytokinins.In our previous study,we found that OsPUP1 may be involved in mediating the unloading and transport of cytokinins in vascular tissues by importing cytokinins into the endoplasmic reticulum,to regulate the development of rice grain and plant types.Following studies found that OsPUP1 also had a regulatory effect on high temperature tolerance in rice.In this thesis,OsPUP1-overexpressing plants are used as experimental materials to make a further study on the mechanism of OsPUP1 in regulating high temperature tolerance in rice.The specific research results are as follows:1.Compared with wild-type Zhonghua 11（ZH11）,the survival rate and seed setting rate of OsPUP1-overexpressing plants under high temperature treatment decreased significantly,and their high temperature tolerance was negatively correlated with the gene expression level.The research has shown that OsPUP1 negatively regulates the high temperature tolerance at the seedling and panicle stage in rice.2.Compared with wild-type ZH11,the content of cytokinin of OsPUP1-overexpressing plants in shoot was reduced.After treatment with 10^-9 M kinetin（KT）,OsPUP1-overexpressing plants have significantly improved high temperature tolerance and increased seedling survival rate.The cytokinin content of OsPUP1-overexpressing plants in the panicle was decreased,which might have contribute to the deterioration of high temperature tolerance at the panicle stage.3.Compared with wild-type ZH11,the growth of dry weight of shoot and total root number of OsPUP1-overexpressing plants were significantly inhibited after high temperature treatment at 42°C for 120 h.4.Scanning electron microscopy results of the leaves of OsPUP1-overexpressing plants showed that the stomatal aperture after the high temperature treatment at 42℃for 2 days was significantly smaller than that of wild-type ZH11,suggesting that the stomatal closure may be the reason for the deterioration of high temperature tolerance of OsPUP1-overexpressing plants.5.The results of physiological indexes showed that high temperature treatment at 42℃would cause the increase of malondialdehyde（MDA）content and relative conductivity,and the increase of these two indexes in OsPUP1-overexpressing plants were significantly greater than that of wild-type ZH11.Besides,with the extension of high temperature treatment time,the chlorophyll content in OsPUP1-overexpressing plants was significantly reduced compared with wild-type ZH11.