Evolution Analysis And Functional Differentiation Of Vps37 Gene Family In Populus Euphratica

Gene families supply raw genetic materials to biological evolution, and functional divergency among copies in gene family is the main driving force in adaptation and species diversity. ESCRT-complexes(endosomal sorting complex required for transport) are specific in eukaryote and Vps37 gene family involved in growth and development process of plants and cellular responses to environmental stress. Populus euphratica is a model tree with high tolerance to salt, drought and other abiotic stresses. It provides an important genetics model to study the mechanism of response to various stresses in trees. In this study, we perform analysis on the size of Vps37 gene family in P. euphratica using phylogenetic evolution methods, and further examine their possible functional divergency though transgenic plants. The results show as below:1) Two copies PeVps37-1 and PeVps37-2 were identified in P. euphratica genome based on distribution of functional domains and motifs, and confirmed by molecular cloning methods. Amino acid sequence analysis shows that both of the two copies have a conservative Mod-r domain which is specific to Vps37 family in plants. The evolution analysis indicated that PeVps37-2 is subject to positive selection(dN/dS>1) and displays faster evolutionary rate than that of in PeVps37-1. Those results suggested that possible function divergency occurred between both of paralogs genes, the potential adaptive evolution for PeVps37-2 might be an important factor determining the response to stresses in P. euphratica.2) The analysis of gene expression pattern showed that under salt stress the spatial and temporal expression of PeVps37-1 and PeVps37-2 are divergent significantly. PeVps37-1and PeVps37-2 expressed in roots, phloem and xylem, little detected in leaves, the expression levels of PeVps37-2 were higher in roots and xylem than that of PeVps37-1. However, after treatments with different concentration of NaCl, both genes were induced to express highly in leaves, but no changed significantly in other tissues. Subcellular localization analysis found both PeVps37-1:GFP fusion protein and PeVps37-2:GFP fusion protein accumulated exclusively in cell membrane and intercellular matrix. The results suggested that Vps37 subunit assist the recruitment of ESCRT-Ⅰto cell membranes, than it contributes to the endosomal recruitment of ESCRT-Ⅱ. ESCRT-Ⅰand ESCRT-Ⅱwork together to help the endosomal invagination and vesicle budding formation via MVBs pathway in cellular matrix.3) Over-expression PeVps37-2 transgenic Arabidopsis thaliana, showed a better growth status and higher germination rate than over-expression PeVps37-1 transgenic Arabidopsis thaliana and Col-0 under the salt stress. Surprisingly, over-expression PeVps37-2 transgenic Arabidopsis thaliana germinated over 75% under the lethal salt concentration of 200 mM NaCl. The root length of over-expression PeVps37-2 transgenic Arabidopsis thaliana is also longer than in that of over-expression PeVps37-1 and Col-0 under the salt stress. The results suggested that the over-expression of PeVps37-2 improve the salt-tolerance of Arabidopsis thaliana.4) To determine the function of PeVps37, PeVps37-1 was overexpressed in transgenic P. tomentosa. The leaves from wild-type and transgenic plants respectively, inoculated with fungus Dothiorella gregaria. Leaves of transgenic lines show larger lesion areas(4-5 folds) caused by fungus infection than that of control lines. These results indicated that overexpression of PeVps37 resulted in an increase of susceptibility to D. gregaria infection in the transgenic poplars.In conclusion, Vps37 gene family are comprised of two copies PeVps37-1 and PeVps37-2 in P. euphratica, in which functional divergency occurred. PeVps37-2 undergo adaptive evolution, and express highly induced by salt stresses, which might contribute to enhance the tolerance to high salt stresses in P. euphratica.