Identification, Classification, and Expression Profiles of Heat Shock Transcription Factors in Tea Plant (Camellia Sinensis) Under Temperature Stress

In vascular plants, heat shock transcription factors (Hsfs) regulate heat stress response by regulating the expression of heat shock proteins. This study systematically and comprehensively analyzed the Hsf family in tea plant [Camellia sinensis (L.) O. Kuntze]. A total of 16 CsHsfs were identified from the transcriptome database of tea plant and analyzed for their phylogenetic relationships, motifs, and physicochemical characteristics. On the basis of the phylogenetic comparison of tea plant with Arabidopsis thaliana, Populus trichocarpa, Theobroma cacao, and Oryza sativa, the CsHsfs were classified into three classes, namely, A (56.25%), B (37.50%), and C (6.25%). Heat mapping showed that the expression profiles of CsHsf genes under non-stress conditions varied among four tea plant cultivars, namely, 'Yunnanshilixiang', 'Chawansanhao', 'Ruchengmaoyecha', and 'Anjibaicha'. Six CsHsf genes (CsHsfA1a, CsHsfA1b, CsHsfA6, CsHsfB1, CsHsfB2b, and CsHsfC1) were selected from classes A, B, and C to analyze the expression profiles of CsHsf genes through quantitative real-time PCR in 'Yingshuang', 'Anjibaicha', and 'Yunnanshilixiang' under high (38 °C) or low (4 °C) temperature stress. Temperature stress positively or negatively regulated all of the selected CsHsf genes, and the expression levels evidently varied even among CsHsf genes belonging to the same class. This study provided a relatively detailed summary of Hsfs in tea plant and may serve as a reference for further studies on the mechanism of temperature stress regulation by CsHsfs.