CsHSFA1b and CsHSFA2 are involved in the heat stress inhibition of catechin biosynthesis
To investigate the function of CsHSFA1b and CsHSFA2 in catechin biosynthesis, we transiently decreased the expression of both these genes in tea leaves using the antisense oligodeoxynucleotide (AsODN) suppression strategy. Firstly, to determine the efficiency of gene suppression at each sampling, we measured the respective transcript levels of CsHSFA1b and CsHSFA2 (Figure 2a). The qRT-PCR results revealed an average inhibition of 49% for CsHSFA1b and 53% for CsHSFA2 (Figure 2a). Relative to the sODN group, the expression levels of catechin biosynthetic genes, includingCsCHS , CsDFR , and CsANS , increased inCsHSFA1b- silenced and CsHSFA2- silenced plants (Figure 2b). Accordingly, the quantification of catechin contents by HPLC showed that leaves from CsHSFA1b -silenced plants accumulated 21% more and those from CsHSFA2- silenced plants accumulated 17% more catechins than control leaves (Figure 2c). Collectively, our results suggest that CsHSFA1b and CsHSFA2 negatively regulate catechin biosynthesis.