Abstract：Rhododendron species have ornamental, economic and medicinal value, while most of the excellent varieties of Rhododendron cultivated at present have poor heat tolerance, and the increase in temperature will seriously affect the normal growth and development of Rhododendron. Heat stress transcription factors (HSFs) plays a key role in the regulation of plant heat shock response or heat tolerance. In this study, phytoene desaturase (RpPDS, OQ628048) and RpHSFC1a (OQ628046) genes of Rhododendron×pulchrum were cloned, and the virus induced gene silencing (VIGS) system was constructed with RpPDS as the reporter gene and Tobacco rattle virus (TRV) as the vector. The bioinformatics of the RpHSFC1a gene and its function in response to high temperature stress were analyzed. Using phenotypic observation, PCR and qPCR methods, TRV could infect and replicate and metastasize in the leaves of Rhododendron×pulchrum, and yellowing will occurred in leaves when the expression of RpPDS gene is inhibited, the result showed that TRV virus-mediated gene silencing system could be applied in Rhododendron×pulchrum. The CDS of the RpHSFC1a gene length totally 891 bp and encodes 296 amino acids, and RpHSFC1a contained HSF_DNA-bind superfamily conserved domain. RpHSFC1a was predicted to be a hydrophilic and transmembrane protein. Phylogenetic analysis showed that RpHSFC1a protein had the highest homology rate with HSFC1 of Diospyros lotus, with a homology of 75.8%. Under heat stress, RpHSFC1a gene was significantly up-expression, the chlorophyll parameters Fv/Fm, PIABS and ETo/RC in the leaves of the strain of RpHSFC1a gene silenced were significantly lower than those of the control group. The DIo/RC was significantly higher than that of the control group. It was shown that the low expression of RpHSFC1a gene could reduce the ability of Rhododendron×pulchrum to resist high temperature stress, and it is speculated that the RpHSFC1a gene participates in the regulatory mechanism of Rhododendron×pulchrum in response to high temperature stress. This study provides a theoretical reference for the study of heat tolerance, and genetic resources for improving the high temperature stress tolerance of Rhododendron.
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