Physiological And Biochemical Responses Of Different Rice Varieties Under Arsenic Stress

Rice is an important grain crop in the world.Under As stress,rice can alleviate stress damage through a series of regulatory mechanisms,but different varieties of rice have great differences in response to As stress.To select arsenic-tolerant varieties,two indica rice[Yuehesimiao(Y)and Meixiangzhan 2(M)] two hybrid rice [Wuyou 308(WY),Guang8Youjinzhan(G)] and two japonica rice [Nipponbare(R),Wuyunjing 7(W)] were used as experimental materials.The 6 rice varieties were treated with As stress at four concentrations(0,40,80,and 120 μmol/L)by hydroponics..The differences in tolerance,accumulation,and physiological and biochemical responses of different rice varieties to arsenic were compared.The effects of multi-gradient As stress on rice phenotypes,accumulation characteristics,and physiological resistance of As were analyzed.Moreover,the transcription levels of As absorption(OsLsi1),transport(OsLsi2,OsLsi6),vacuole isolation(OsABCC1),and plant chelate peptide synthesis(OsPCS1)gene expression were detected.On this basis,the As tolerance index of different rice varieties was calculated and evaluated by membership function.At the same time,correlation analysis and multivariate statistical analysis of all rice indicators were carried out.The main research results and conclusions are as follows:1.With the increase of As stress concentration,rice growth showed two phenomena:inhibition and "low promotion and high inhibition".The plant height and biomass of Wuyou308,Guang8 Youjinzhan,Nipponbare and Wuyunjing 7 were inhibited under As stress.The growth of plant height and biomass of Yuehesimiao and Meixiangzhan 2 showed a phenomenon of "low promotion and high inhibition".In addition,As stress inhibited root length and elongation of 6 rice varieties.2.Different rice varieties had different absorption and accumulation characteristics of As under different concentrations of arsenic stress.When the As concentration was 40μmol/L,Wuyunjing 7 had the lowest As content in both root and ground parts of rice.The highest translocation coefficients were Yuehesimiao and Meixiangzhan 2,respectively,and Yuehesimiao had the lowest.When the As content was 80 μmol/L,the lowest was Wuyunjing 7,and the highest was Guang8 Youjinzhan.On the ground,the lowest is Guang8 youjinzhan,the highest is Wuyou 308,and Guang8 youjinzhan has the lowest transport coefficient.When the As content was 120 μmol/L,the lowest was Wuyunjing 7,and the highest was Wuyou 308.On the ground,the lowest is Guang8 Youjinzhan,the highest is Nipponbare,and the smallest transport coefficient is Guang8 youjinzhan.3.With the increase of As stress concentration,the activities of SOD and POD and the contents of MDA,NPT,GSH and ANT of the six rice varieties increased first and then decreased,but the sensitivity of these indexes to arsenic stress concentration was different.CAT and PCs were different from the above indexes,and CAT activity decreased under all arsenic concentrations.The PCs contents of Guang8 Youjinzhan,Meixiangzhan 2,Yuehesimiao and Wuyunjing 7 showed a trend of first increasing and then decreasing with the increase of As concentration.The contents of PCs in Wuyou 308 and Nipponbare decreased and increased with the increase of As concentration,respectively.4.There were differences in the response of rice varieties to arsenic stress in the expression of absorption,transport,vacuole isolation and chelate peptide synthesis genes.Under arsenic stress,OsLsi1 was downregulated in the roots of 4 varieties Yuehesimiao,Meixiangzhan 2,Wuyou 308 and Nipponbare,OsLsi2 was regulated in the roots of 5varieties except Wuyunjing 7,OsLsi6 was regulated in the roots of Nipponbare and OsABCC1 was regulated in the roots of Nipponbare and Wuyou 308.And relative expression of OsPCS1 in the roots of Yuehesimiao,Nipponbare and Wuyunjing 7.Arsenic stress up-regulated OsLsi2 in the above-ground parts of 6 varieties of rice,and the roots of Meixiangzhan 2,Wuyou 308,Guang8 Youjinzhan,Wuyunjing 7 and the roots of Yuehesi seedling,Meixiangzhan 2,Guang8 Youjinzhan,Nipponbare,Wuyunjing 7 OsLsi6.The expression of OsABCC1 in the roots and aboveground parts of Yuehesimiao,Nipponbare,Meixiangzhan 2,Guang8 Youjinzhan and above-ground parts of Wuyunjing 7,as well as OsPCS1 in above-ground parts of 6 rice varieties.5.The results of As tolerance analysis showed that the tolerance index of Meixiangzhan 2 was the highest under 80 and 120 μmol/L arsenic stress,and when the concentration increased to 120 μmol/L,the tolerance index of Meixiangzhan 2 dropped to intermediate type.The tolerance index of other varieties was lower than that of Meixiangzhan 2.Correlation analysis showed that As content was significantly correlated with plant height,CAT,and the expression of OsLsi1,OsLsi2,OsLsi6,OsABCC1 and OsPCS1 genes..Multivariate statistical analysis showed that rice treated with different concentrations of As achieved partition on the distribution plot.