Genome-wide identification of HSF family in peach and functional analysis of PpHSF5 involvement in root and aerial organ development

Heat shock factors (HSFs) play important roles during normal plant growth and development and when plants respond to diverse stressors. Although most studies have focused on the involvement of HSFs in the response to abiotic stresses, especially in model plants, there is little research on their participation in plant growth and development or on the HSF (PpHSF) gene family in peach ( ). DBD (PF00447), the HSF characteristic domain, was used to search the peach genome and identify . Phylogenetic, multiple alignment and motif analyses were conducted using MEGA 6.0, ClustalW and MEME, respectively. The function of was confirmed by overexpression of into Arabidopsis. Eighteen genes were identified within the peach genome. The genes were nonuniformly distributed on the peach chromosomes. Seventeen of the (94.4%) contained one or two introns, except , which contained three introns. The in silico-translated PpHSFs were classified into three classes (PpHSFA, PpHSFB and PpHSFC) based on multiple alignment, motif analysis and phylogenetic comparison with HSFs from and . Dispersed gene duplication (DSD at 67%) mainly contributed to HSF gene family expansion in peach. Promoter analysis showed that the most common cis-elements were the MYB (abiotic stress response), ABRE (ABA-responsive) and MYC (dehydration-responsive) elements. Transcript profiling of 18 showed that the expression trend of was consistent with shoot length changes in the cultivar 'Zhongyoutao 14'. Further analysis of the was conducted in 5-year-old peach trees, and , respectively. Tissue-specific expression analysis showed that was expressed predominantly in young vegetative organs (leaf and apex). Subcellular localization revealed that PpHSF5 was located in the nucleus in cells. Two transgenic Arabidopsis lines were obtained that overexpressed . The root length and the number of lateral roots in the transgenic seedlings were significantly less than in WT seedlings and after cultivation for three weeks. The transgenic rosettes were smaller than those of the WT at 2-3 weeks. The two transgenic lines exhibited a dwarf phenotype three weeks after transplanting, although there was no significant difference in the number of internodes. Moreover, the PpHSF5-OE lines exhibited enhanced thermotolerance. These results indicated that PpHSF5 might be act as a suppresser of growth and development of root and aerial organs.