Cell cycle transcription factor E2F2 mediates non-stress temperature response of AtHSP70-4 in Arabidopsis.

AtHSP70 expression exhibits both stress and non-stress temperature response, however, the molecular mechanisms underlying these temperature signaling pathways remain elusive. Here we performed truncation and deletion assay to investigate the cis-elements within the promoter region of AtHSP70-4 (AT3G12580). And found the region between -1000 and -1100 bp from the translation initiation site (TIS) was indispensable for the non-stress temperature response of AtHSP70. Further deletion assay of several candidate motifs within this region suggested that one 'GCGCCAAA' sequence played the critical role. This motif was found as the reverse DNA-binding motif of cell cycle transcription factor E2F family. EMSA assay verified one number of Arabidopsis E2F family-E2F2 could bind to AtHSP70-4 promoter via this motif. These results indicated the temperature regulated expression of AtHSP70-4 may be mediated by cell cycle transcription factors and participate in plant acclimations to non-stress temperature changes.