CsMYBL2 homologs modulate the light and temperature stresses-mediated anthocyanin and catechins biosynthesis in tea plants (Camellia sinensis).

Anthocyanin and catechins production in tea (Camellia sinensis) leaves can positively affect tea quality, however, their differential regulations are not fully understood. Here we report that, while the CsMYB75- or CsMYB86-directed MYB-bHLH-WD40 (MBW) complexes differentially activate anthocyanin or catechins biosynthesis in tea leaf, respectively, CsMYBL2a and b homologs negatively modified the light- and temperature-induced anthocyanin and catechins production in both Arabidopsis and tea plants. The MBW complexes activated both anthocyanin synthesis genes and downstream repressor genes CsMYBL2a and 2b. Overexpression of CsMYBL2b, but not CsMYBL2a, repressed Arabidopsis leaf anthocyanin accumulation and seed coat proanthocyanin production. CsMYBL2b strongly, but CsMYBL2a weakly, repressed the CsMYB75/CsMYB86 activation of CsDFR and CsANS, due to their different EAR and TLLLER domains and interactions with CsTT8/CsGL3 in interfering with the functions of MBW activation complexes. CsMYBL2b and 2a in tea leaves play different roles in fine-tuning CsMYB75/CsMYB86-MBW activation of biosynthesis of anthocyanins and catechins, respectively. The CsbZIP1-CsmiR858a-CsMYBL2 module mediated the UV-B- or cold-activated CsMYB75/CsMYB86 regulation of anthocyanin/catechins biosynthesis by repressing CsMYBL2a and 2b. Similarly, the CsCOP1-CsbZIP1-CsPIF3 module, and BR signaling as well, mediated the high-temperature repression of anthocyanins and catechins biosynthesis through differentially up-regulating CsMYBL2b and 2a, respectively. The study provides new insights into the complex regulatory networks in environmental stresses-modified flavonoid production in tea plant leaves.