Genome-Wide Analysis of Heat Shock Transcription Factors in Ziziphus jujuba Identifies Potential Candidates for Crop Improvement Under Abiotic Stress

Plant heat shock transcription factors (Hsfs) play a significant role in adoption under abiotic stress conditions by modulating the expression of several stress-responsive genes. Analysis of the Hsf gene family will serve to understand the molecular mechanism which is involved in response to abiotic stress. The Ziziphus species grows in warm and dry regions and is inherently tolerant to abiotic stress conditions; thus, Ziziphus is a highly enriched source of genes conferring abiotic stress tolerance. Therefore, the present study provides a comprehensive genome-wide analysis of the Hsf gene family in Z. jujuba. Identified 21 non-redundant Hsf genes were grouped into three major classes (classes A, B, and C) based on the phylogenetic analysis. Promoter and gene ontology analysis suggested that ZjHsfs perform diverse functions in response to abiotic stress conditions. Two paralogous pairs resulting from tandem gene duplication events were identified. Also, physio-chemical properties of chromosomal locations, gene structure, motifs, and protein domain organization of Hsfs were analyzed. Real-time PCR expression analyses revealed that most of the Z. jujuba Hsf genes are differentially expressed in response to heat stress. The analysis suggested ZjHsf-2, ZjHsf-3, ZjHsf-5, ZjHsf-7, ZjHsf-8, ZjHsf-10, ZjHsf-12, ZjHsf-17, and ZjHsf-18 were the outstanding candidate genes for imparting heat stress tolerance and for future functional analysis. The present analysis laid the foundation for understanding the molecular mechanism of the Hsf gene family regulating Z. jujuba development and tolerance to abiotic stress conditions.