Genome-wide analysis of tomato WIP family genes and their response to salt stress under glutathione treatment

Cys2His2 (C2H2)-type zinc-finger proteins (ZFPs) participate in plant tolerance under various abiotic stresses. Wound-induced protein (WIP) is a subfamily of the C2H2-ZFP family, but WIP family is largely unknown in tomato (Solanum lycopersicum L.), which is an important salt sensitive vegetable crop. We analyzed the tomato WIP gene family using bioinformatics in order to uncover the involvement of tomato WIPs in responses to salt stress. We identified a total of six putative tomato WIP genes (SlWIPs). The results of our phylogenetic analysis determined that the SlWIP genes are all found in three subfamilies. SlWIPs all have features commonly found in the C2H2 family, as well as highly conserved WIP domains. Sequence analysis determined that a majority of SlWIP genes had only one intron. The six identified SlWIP geneswere scattered across six chromosomes. An assessment of the cis-elements determined that the promoters of SlWIPs possessed a number of abiotic stress and phytohormones signal responsive cis-elements. An SlWIP gene family heatmap demonstrated that SlWIP1/2/3/4/6 have low expression level under the NaCl treatment and high expression level under the NaCl + GSH treatment. SlWIP5 showed same expression level in NaCl and NaCl + GSH treatment. We used real-time quantitative PCR to assess the levels of SlWIP gene expression, finding that under salt stress, there were significantly up-regulated levels of SlWIP2, SlWIP4 and SlWIP5 expression. GSH significantly up-regulated the relative expression levels of both SlWIP1 and SlWIP6 when subjected to salt stress. This study assesses how the SlWIP family is associated with salt tolerance and will serve as an important resource when elucidating the evolutionary progression of the SlWIP family.