Determination of expansin genes in cucumber and zucchini genomes and evaluation of gene expression profiles under abiotic stress conditions

Zucchini and cucumber belong to the Cucurbitaceae family, including important agricultural products that are nutritionally and economically valuable. The expansin gene family is an important gene family that plays a role in both the growth and development of plants and stress tolerance. Although the expansin proteins have been identified at the genome level in various plants, no study has been conducted so far to identify and characterize these proteins in zucchini and cucumber using whole genomic data. In this study, it was aimed to characterize the expansin genes and protein products identified in the zucchini (Cucurbita pepo) and cucumber (Cucumis sativus) genomes by using bioinformatics methods and to determine the gene expression levels in tissue samples treated with various abiotic stresses. As a result of the analysis, 49 and 41 expansin genes were determined in the zucchini and cucumber genomes respectively. Expansin proteins, whose cellular location, biological functions and molecular functions are identified by gene ontology analysis, generally consist of α helix and β layer structures. Orthologous relationships of zucchini and cucumber expansin genes with model organisms Arabidopsis thaliana, Glycine max, Oryza sativa and Populus triocarpa were examined and the highest number of orthologous gene pairs was found in soybean for both plant species. According to micro-RNA (miRNA) analysis, the most miRNAs targeting zucchini expansin genes were miR164 and miR395, and the most miRNAs targeting cucumber expansin genes were miR156, miR159, miR164, miR168 and miR395. Among the expansin genes whose gene expression profiles were determined, CsEXPB-04 and CsEXPA-11 in cucumber, CpEXPA-20 and CpEXPLA-14 in zucchini are thought to be prominent genes in abiotic stress response in addition to their role in the normal development process of the plant, in line with the transcriptome data and ortholog studies. This study provides valuable data that will contribute to the elucidation of the roles of expansin genes in the resistance mechanism in detail and to the cultivation of plants with high stress resistance by performing advanced functional analyzes.