Screening And Functional Study Of Interacting Proteins Of Arabidopsis Thaliana Ca²⁺/H⁺ Antiporter Family （CAXs）

Arabidopsis thaliana CAXs are a member of a multi gene family, which are mainly found in the plasma membrane or the vacuole membrane, and they have 11 transmembrane domains. CAXs can use the pH gradient established by the ion pump to transport Ca2+from the cytoplasmic matrix to regulate the changes of Ca2+content in plant cells. In order to understand the role of Arabidopsis Ca2+/H+antiporter family CAXs play in the plant response to ion stress, a preliminary study on the function of the AtCAXs in Arabidopsis thaliana was carried out.In this study, the yeast two hybrid technique was used to screen the members of Arabidopsis thaliana CAXs, and the results showed that there may have an interaction between AtCAXl and N terminal of AtCAX4, double molecule fluorescence experiments then obtained the same results. Further analysis of the excessive expression of AtCAXl and AtCAX4 in yeast for different ion stress responses, show that AtCAX1 and AtCAX4 are able to enhance the tolerance of yeast strain k667 to Na+, Ca2+and Ba2+.The expression characteristics of AtCAX1 and AtCAX4 were analyzed by real-time quantitative PCR. The results showed that AtCAXl expression was highest in the silique of wild Arabidopsis thaliana, and the lowest expression was in the root. The expression of AtCAX4 gene was highest in the root of wild Arabidopsis thaliana, and the expression of was the smallest in the stem. Na+, Ca2+and Ba2+stress treatment can induce the expression of AtCAX1 and AtCAX4 genes in the shoot and root. The phenotype of over expression of AtCAXl and AtCAX4, mutant (atcaxl, atcax4) and double mutant (atcaxl/atcax4) analysis under salt stress treatment showed that AtCAXl and AtCAX4 over expression plants grew better than wild type, while atcaxl, atcax4 and atcaxl/atcax4 plants increased the sensitivity to Na+, Ca2+ and Ba2+ compared with the wild type. The results of the study showed that the over expression and mutant of AtCAX1 and AtCAX4 genes had a certain effect on the ability of resistance to ion stress in Arabidopsis thaliana, it played an important role in the plant response to ion stress, which provids a theoretical basis for further revealing the function of the CAX protein family.