2.7 BES1 directly targets APX2 and HSFA3 in the
memory phase
Since BES1 is critical for the sustained activation of HS-associated
memory genes, we further examine whether BES1 directly target these
genes for activation. Yeast one-hybrid (Y1H) assays indicate that BES1
directly activates the expression of APX2 and HSFA3 (Fig.
6A). We next conducted an electrophoretic mobility shift assay
(EMSA) towards the fragment of APX2 and HSFA3 promoter
containing an E-box, the potential BES1 protein binding site. As
expected, the EMSA assay showed that MBP-BES1 proteins could bind to
APX2 and HSFA3 probes, but MBP did not (Fig. 6B, C). We further
confirmed that BES1 directly binds to the promoter of APX2 andHSFA3 in vivo using a chromatin immunoprecipitation (ChIP)-qPCR
assay. Obvious enrichment was found in the promoter of APX2 andHSFA3 (Fig. 6D). These results suggest that APX2 andHSFA3 are transcriptional targets of BES1 proteins during the
thermomemory process.