Genome-wide identification and expression analysis of watermelon (Citrullus lanatus) SSR2 gene during fruit development

Abstract

Background

Sterol side-chain reductase 2 (SSR2) is a key enzyme in the synthesis of plant cholesterol pathway. Despite the importance of watermelon as a horticultural cash crop, the SSR2 gene in watermelon has not been previously studied or reported.

Results

In this study, 28 SSR2 genes were identified in the watermelon genome. The physicochemical properties of 28 ClaSSR proteins were predicted by bioinformatics methods, and the gene structure, conserved motif, chromosome localization, phylogenetic analysis, cis-acting elements, expression patterns, promoter activity analysis and subcellular localization of ClaSSRs were studied. The 28 ClaSSRs were unevenly distributed on 11 chromosomes, and phylogenetic analysis showed that they could be grouped into 4 groups with other related Cucurbitaceae homologous genes. Analysis of gene structure and motifs revealed similarities in exons/introns and motifs between members of the same group, further supporting phylogenetic results. The RT–qPCR results showed variations in ClaSSRs expression during watermelon fruit development. The analysis of promoter activity for ClaSSR25 showed strong activity. Subcellular localization studies confirmed that ClaSSR25 is mainly located in the cytoplasm, which aligns with the predicted outcomes. We additionally estimated the network of protein–protein interactions for ClaSSR25 and analyzed proteins that could potentially interact with ClaSSR25 in melon and Arabidopsis thaliana.

Conclusions

We conducted bioinformatics analysis and expression analysis of members of the watermelon SSR2 gene family in this work, and the outcomes set the stage for further investigations into the watermelon SSR2 gene.

Graphical Abstract