Genome-wide identification and analysis of heat shock transcription factor family in cucumber (Cucumis sativus L.)

Heat shock transcription factor (HSF) plays an important role in the expression regulation of thermal response genes in plants. However, little is known about this family in cucumber. Recently, the availability of cucumber genome sequences has provided an opportunity for identifying these Hsfs. In the present study, all members of the HSF gene family of cucumber (Cucumis sativus L.) were identified from the sequenced genome and analyzed in silico. We identified at least 21 HSF genes in the cucumber, which encode proteins with length between 184 and 560 amino acids. Multiple sequence alignments showed that cucumber HSF proteins possess highly conserved DNA binding domains and other extensively conserved motifs. These HSF genes are unevenly distributed in all seven chromosomes, with chromosomes 2 and 3 both having the greatest number of HSF genes. In addition, phylogenetic analysis of the HSFs from cucumber and Arabidopsis thaliana showed that these proteins could be divided into three families (A, B and C). The A family was then further divided into nine subfamilies, and there were eight pairs of orthologous genes and five pairs of paralogous genes. HSF members in some subfamilies were from cucumber and Arabidopsis, indicating that the HSF gene family existed before the separation of cucumber and Arabidopsis thaliana.