Identification, characterization of HSP (heat shock protein) family members in watermelon and analysis of gene expressions under drought and heat stresses

Heat shock (Hsp) genes have vital importance for organisms. This gene family is divided into six classes and found in all living organisms. In this study, Hsp gene families in watermelon were identified and studied by bioinformatics analysis. Besides, expression profiles of genes under combined drought and heat stress conditions were experimentally analyzed and the results were compared by bioinformatics analyzes. In watermelon genome, 39 gene belonging to sHsp family, 101 gene belonging to Hsp40 family, 23 gene belonging to Hsp60 family, 12 gene belonging to Hsp70 family, 6 gene belonging to Hsp90 family and 102 gene belonging to Hsp100 family were found. It is also seen that the proteins in the same clade in the constructed phylogenetic trees had similar motif patterns. When the estimated three-dimensional structures of proteins belonging to these genes are examined, it has been determined that α-helical structure was dominant in almost all families. In gene ontology analysis, it has been observed that molecular functions of those proteins were mostly by binding. A significant increase was detected usually at 30 minutes in almost all samples (root, stem, leaf, shoot) for studied gene families when real time-PCR was used to assess the gene expression levels under combined stress conditions. This study provides an extensive information for watermelon Hsps and can enhance our knowledge about the relationships between Hsp genes and combined stresses. Consequently, it is thought that this study can be carried forward to further steps and can be beneficial for watermelon breeding.