Genomic, evolutionary and expression profile analysis of Hsp70 superfamily in A and D genome of cotton ( Gossypium spp.) under the challenge of Verticillium dahliae

In this study, we comparatively analyzed the 115 Hsp70 genes identified in Gossypium raimondii , Gossypium hirsutum and Gossypium arboreum genomes. Those Hsp70 genes unequally distributed among chromosomes in A and D genome of cotton ( Gossypium spp.), and were classified into 29 groups according to the homology of them. Based on the localization information of the orthologs in Arabidopsis, the Hsp70 proteins were predicted to locate in cytosol, endoplasmic reticulum, mitochondrion or chloroplast. Homologous analysis indicated the evolutionary conservation of Hsp70 in cotton. In addition, those Hsp70 genes were differently expressed in Suyuan-045, Hai-7124 and TM-1, which were highly resistant, resistant, and sensitive to Verticillium dahliae respectively. The expressions of 26 Hsp70 genes were induced by Verticillium dahliae except for Hsp70-07/16/25/26 , and the result suggested the potential involvement of them in responding to Verticillium wilt. Hsp70-08/30/31 was highly expressed in both Suyuan-045 and Hai-7124, and it was hypothesized that they might be involved in the resistance to the invasion of Verticillium dahliae . 144h after inoculation with Verticillium dahliae , the expression of Hsp70-13/14/15 was only up-regulated in Suyuan-045, and it was assumed that they might be involved in resistance to the extension of Verticillium dahliae . Further study on those Hsp70 genes would be valuable to reveal the role of them in Verticillium wilt resistance.