| Enhancing the salt tolerance of rice is of great significance for increasing rice yield.A TIP-like gene of aquaporin,named OsAQP,was isolated from the cDNA library of young panicles of rice in our laboratory.Previous studies have found that the expression of OsAQP gene is regulated by various factors,including high salt and drought,hormones such as abscisic acid can induce the up-regulation of OsAQP expression,suggesting that this gene may be associated with abiotic stress responses such as salt stress.To identify the function of OsAQP,the laboratory constructed the OsAQP transgenic Arabidopsis thaliana.In this study,OsAQP transgenic Arabidopsis thaliana was used as a material,and 50,100,125 and150 mM gradient salt stress treatment showed that the germination rate,root length and fresh weight of transgenic Arabidopsis were at least 17%,40.8%and 14.29%higher than the control,respectively,and the difference reached a significant level.Under normal conditions,APX activity in leaves of transgenic plants was higher than that in WT.After treatment with 300 mM NaCl,the activities of three other antioxidant enzymes(SOD,POD,APX)in transgenic Arabidopsis leaves were increased,and the difference reached significant level.The MDA content also increased after treatment,but the content in the transgenic plants was 37.5%lower than that of WT,and the difference reached a significant level.It is suggested that OsAQP overexpression can not only promote the seed germination and root growth of Arabidopsis thaliana,but also enhance the endogenous antioxidant enzyme activity of Arabidopsis and reduce the degree of membrane lipid peroxidation under salt stress,which enhances the transgenic plants to a certain degree of salt stress tolerance.To study the salt tolerance mechanism of transgenic Arabidopsis thaliana,this study determined the expression of Arabidopsis stress-related marker genes RbohD,Zat12,Cu/ZnSOD,WRKY25,PR-1,AtSOS2and ABA response-related genes ABF3 and ABF4.At salt treatment for 4 h and 12 h,the expression levels of ABF3,ABF4,AtSOS2 and PR-1 in transgenic Arabidopsis were higher than those in WT,while the expression of Zat12 in transgenic Arabidopsis was lower than that in WT.At 4 h after salt treatment,the expression of Cu/ZnSOD in transgenic Arabidopsis was higher than that in WT.At 12 h after salt treatment,the expression of RbohD and WRKY25 in transgenic Arabidopsis was higher than that in WT,and the difference are reached extremely significant levels.It is suggested that the increase of salt tolerance in transgenic Arabidopsis by OsAQP heterologous overexpression may be related to the enhancement of ABA signaling in Arabidopsis by increasing the expression level of stress-related genes in Arabidopsis.In order to identify the function of this gene in rice,OsAQP overexpressing transgenic rice was constructed and screened and identified.The study found that under normal culture conditions,the germination rate of transgenic rice was higher than that of WT.In the 2nd day,the germination rates of three transgenic rice lines(OsAQP-4,OsAQP-9,OsAQP-12)were 33.67%and 42.86%,38.78%respectively and the germination rate of WT was only 10.2%;In the 4th day,the germination rate of transgenic rice was 95.92%,98.98%,96.94%,and WT was 93.88%;In the 6th day,WT and transgenic rice were germination completly,indicating that OsAQP overexpression promotes seed germination of rice.Statistical analysis of the agronomic shape of OsAQP overexpressing transgenic rice T1 generation showed that compared with wild type,transgenic rice showed an increase in plant height,total grain number,solid grain number,and seed setting rate,and both reached extremely significant differences.Under gradient salt stress,the shoot and root length of transgenic rice were higher than WT and reached significant difference.When treated with 75 mM NaCl,the shoot of transgenic rice was 2.31,1.81and 2.09 times of WT,respectively.The length of root was 1.84,1.56 and 1.49 times of WT,respectively,this indicates that overexpression of OsAQP contributes to the growth of transgenic rice under salt stress.In order to further study the functional mechanism of OsAQP overexpression in rice salt tolerance,the expression of rice ion transport related genes was detected.Under normal conditions,OsHKT1;1,OsHKT2;2 and OsHKT2;4 were expressed in transgenic rice than those in WT;at 5 h after salt treatment,except for OsHKT1;5,the expression of other genes in transgenic rice was higher than that of WT,and reached extremely significant difference.Before treatment,the expression levels of OsNHX1,OsNHX3 and OsNHX5 genes in transgenic rice were higher than those in WT,and reached extremely significant differences.After salt treatment,except for OsNHX1,other OsNHX gene family members expressed high levels in transgenic rice,the expression level of OsNHX2 is 6.71 times that of WT.The expression level of OsSOS1 gene salt in transgenic rice was lower than that of WT,however,after salt treatment,the expression level of OsSOS1 in transgenic rice was significantly higher than that of WT,which was 3.27times that of WT.One of the reasons for OsAQP gene overexpression enhances salt tolerance in rice is that to activate the expression of ion transport-related genes,and to regulate the cells osmotic balance by accelerating the transport of Na~+and K~+,and to maintain the normal biological processes of cells.In this study,OsAQP was overexpressed in transgenic Arabidopsis thaliana and Oryza sativa to identify the function of OsAQP.It was found that overexpression of OsAQP can promote seed germination and root growth of Arabidopsis and rice,and improve plant salt tolerance to a certain extent.Receptivity,its molecular mechanism may involve changes in the expression levels of some known stress-related genes,ion transport-related genes,and is associated with the ABA signaling pathway.This study lays the foundation for the subsequent exploration of the functional mechanism of OsAQP,and may also provide new candidate genes for the cultivation of salt-tolerant rice varieties. |
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