Study On Physiology,biochemistry And Transcriptomics Of Rice In Response To High Temperature Stress During Meiosis

Rice is the most important crop in the world,supporting half people in the world.In recent years,with the continuous changes of the global climate,high temperature stress has seriously affected the growth and development of rice and yield,and brought serious harm to world food security.Therefore,analyzing the heat-resistant mechanism of new heat-resistant germplasm resources is very important for rice variety.In this study,through the analysis of physiological and biochemical changes,four different resistant rice varieties showed different response to heat stress in terms of leaf photosynthetic characteristics,pollen vigor,pollination characteristics,and antioxidant enzyme activities;transcriptome analysis was used to show that the difference between the two germplasms of the sensitive variety MH101 and the heat-tolerant variety SDWG005 in the high temperature,to clarify the reason why the resistant variety has higher heat tolerance,and to provide a reference for breeding rice varieties with excellent high temperature resistance;finally,comparing the content of flavonoids and lignin and correlation with seed setting rate and pollen vigor in 8 rice varieties,to explore the response of flavonoids and lignin to high temperature stress.The results about 5 sides:(1)High temperature stress has a greater impact on the photosynthesis process in different resistant varieties.The occurrence of photosynthetic disturbance based on stomatal restriction under high temperature stress is very significant in GLA15,and its main characteristic is that with decrease of the stomatal conductance(Gs),the net photosynthetic rate(Pn),the intracellular carbon dioxide concentration(Ci)and the transpiration rate(Tr)decreased.With the extension of high temperature stress time,the net photosynthetic rate of GLA15 is higher than MH101.In addition,the oxygen sensitivity of SDWG005 and MH101 increased under high temperature stress,and SDWG005 was relatively higher.By comparing the PIB of different rice varieties,finding that the CO2 burst of SDWG005 under high temperature stress is significantly stronger than MH101,indicating that SDWG005 has stronger photorespiration under high temperature stress.These results implied that high temperature stress will lead to the decline of photosynthetic capacity of plants,but the plant will slow down the damage caused by high temperature stress through its specific response mechanism.High temperature stress significantly reduced the pollen vigor,the degree of anther cracking,the number of stigma pollination and the seed setting rate of different resistant and sensitive rice varieties.The sensitive rice MH101 was more affected by high temperature.High temperature stress significantly reduced the activities of various antioxidant enzymes(SOD,POD,APX)in the leaves of the sensitive rice variety MH101.(2)After transcriptomics sequencing,cluster analysis found that the resistant variety SDWG005 maintains the steady-state balance of the metabolic process,which is an important reason for its strong heat tolerance.Through enrichment analysis of GO and KEGG pathways,it is found that the heat-resistant mechanism in SDWG005 is related to the reprogramming of cell activities,such as the response to abiotic stress and metabolic reorganization.On the contrary,the down-regulated genes in MH101 seem to be involved in DNA replication and DNA repair proofreading,which caused serious damage to reproductive development when encountering high temperatures during meiosis.In addition,we identified 77 and 11 differentially expressed genes(DEGs)involved in the biosynthetic pathways of lignin and flavonoids,respectively.In addition,we found that SDWG005 has more lignin deposition and flavonoid accumulation in young ears than MH101 under high temperature stress.The results indicate that the biosynthetic pathways of lignin and flavonoids may play an important role in the heat tolerance of rice during meiosis.(3)The content of lignin and flavonoids in different rice varieties increased to varying degrees under high temperature stress,and there was a positive correlation with the seed setting rate.This result indicates that the increased content of lignin and flavonoids may enhance the resistant of rice to high temperatures.