REGULATION OF BZIPS ON METABOLISM OF FLAVONOIDS
Recently, a plenty of flavonoids
show significant contributions to plant tolerances to abiotic stresses
(Agati et al., 2012; Pi et al., 2016, 2018, 2019; Yamasaki et al., 1997;
Yan, et al., 2014). Interestingly, many bZIP transcription factors
usually play a key regulatory roles in the process of flavonoid
biosynthesis. They regulate the expression of key enzyme genes in the
synthetic pathway, thereby regulating the metabolism and synthesis of
flavonoids.
Matousek et al. (2010) found that
both hop HlbZIP1 and HlbZIP2 could activate the expression of chalcone
synthase chs_H1 and the O-methyl transferase 1 genes to
regulate the accumulation of flavonoid glycosides and anthocyanins.
Akagi et al. (2012) found that ectopic DkbZIP5 overexpression in
persimmon calluses could induced the up-regulation of DkMyb4 and
then affect the seasonal biosynthesis of proanthocyanidins in persimmon
fruit. Malacarne et al. (2016) showed that VvibZIPC22, a member of clade
C of the grapevine bZIP family, was able to activate the transcriptional
expression of specific genes of the flavonoid pathway includingVviCHS3 , VviCHI , VviFLS1 and VviANR , alone
or together with other factors to participate in the biosynthesis of
flavonols during flowering and UV light-mediated induction. Dash et al.
(2017) found that the poplar PatbZIP1 transcription factor regulated the
expression of two flavonol synthase genes PtaFLS2 andPtaFLS4 in the flavonoid synthesis pathway to promote the
synthesis of related flavonoids and thus promotes the lateral root
formation. bZIP transcription factor HY5 plays a multifaceted role in
plant growth and development. Apple MdHY5 gene, induced by light
and abscisic acid treatments, promoted anthocyanin accumulation by
regulating expression of the MdMYB10 gene and downstream
anthocyanin biosynthesis genes (An et al., 2017a). Zhang et al. (2011b)
found that the protein levels of two bZIP transcription factors
AtbZIP56/HY5 and AtbZIP64/HYH in Arabidopsis thaliana induced the
accumulation of anthocyanins under low temperature induction. In
addition, ABA can induce the expression of Artemisia annuaAabZIP1 to activate the expression of downstream gene ADSand CYP71AV1 , thereby regulating the biosynthesis of artemisinin
(Zhang et al., 2015a). Fan et al. (2019) showed that the expression ofRsbZIP011 and RsbZIP102 was significantly up-regulated in
radish tissue with higher anthocyanin content under heat and salt
stress.
So far, the bZIPs that involve in flavonoid synthesis varies from plant
species and their target genes (coding for different enzymes in
flavonoid metabolism). To uncover the relationship between bZIP
subfamilies and flavonoid synthesis, all the functional annotated bZIPs
were also categorized into the 13 known subgroups according to CorrĂȘa et
al. (2008) (Table III and Figure I). It seems that only bZIPs in
subfamilies A, H and S could regulate flavonoid metabolism.