Genome-wide identification and classification of the Hsf and sHsp gene families in Prunus mume, and transcriptional analysis under heat stress

The transcriptional activation of heat shock proteins (Hsps) by heat shock transcription factors (Hsfs) is presumed to have a pivotal role in plant heat stress (HS) response. Prunus mume is an ornamental woody plant with distinctive features, including rich varieties and colors. In this study, 18 Hsfs and 24 small Hsps (sHsps) were identified in P. mume. Their chromosomal locations, protein domains, conserved motifs, phylogenetic relationships, and exon–intron structures were analyzed and compared with Arabidopsis thaliana Hsfs or sHsps. A total of 18 PmHsf members were classified into three major classes, A, B, and C. A total of 24 PmsHsps were grouped into eight subfamilies (CI to CIII, P, endoplasmic reticulum, M, and CI- or P-related). Quantitative reverse transcription PCR analysis revealed that members of the A2, A7, and A9 groups became the prominent Hsfs after heat shock, suggesting their involvement in a key regulatory role of heat tolerance. Most of the PmsHsp genes were up-regulated upon exposure to HS. Overall, our data contribute to an improved understanding of the complexity of the P. mume Hsf and sHsp gene families, and provide a basis for directing future systematic studies investigating the roles of the Hsf and sHsp gene families.