CsMYBL2 homologs modulate the light and temperature stress‐regulated anthocyanin and catechins biosynthesis in tea plants (Camellia sinensis)

SUMMARY Anthocyanin and catechin production in tea (Camellia sinensis) leaves can positively affect tea quality; however, their regulatory mechanisms are not fully understood. Here we report that, while the CsMYB75‐ or CsMYB86‐directed MYB–bHLH–WD40 (MBW) complexes differentially activate anthocyanin or catechin biosynthesis in tea leaves, respectively, CsMYBL2a and CsMYBL2b homologs negatively modified the light‐ and temperature‐induced anthocyanin and catechin production in both Arabidopsis and tea plants. The MBW complexes activated both anthocyanin synthesis genes and the downstream repressor genes CsMYBL2a and CsMYBL2b. Overexpression of CsMYBL2b, but not CsMYBL2a, repressed Arabidopsis leaf anthocyanin accumulation and seed coat proanthocyanin production. CsMYBL2b strongly and CsMYBL2a weakly repressed the activating effects of CsMYB75/CsMYB86 on CsDFR and CsANS, due to their different EAR and TLLLFR domains and interactions with CsTT8/CsGL3, interfering with the functions of activating MBW complexes. CsMYBL2b and CsMYBL2a 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/catechin biosynthesis by repressing CsMYBL2a and CsMYBL2b. Similarly, the CsCOP1–CsbZIP1–CsPIF3 module, and BR signaling as well, mediated the high temperature repression of anthocyanin and catechin biosynthesis through differentially upregulating CsMYBL2b and CsMYBL2a, respectively. The present study provides new insights into the complex regulatory networks in environmental stress‐modified flavonoid production in tea plant leaves. Significance Statement It is not clear how tea (Camellia sinensis) leaves control the biosynthesis and accumulation of catechins, anthocyanins, and other types of flavonoids under various environmental conditions. In the present study we show that two MYB repressors (CsMYBL2b and CsMYBL2a) differently fine‐tune the high temperature‐ or light stress‐regulated anthocyanin and catechin production through interfering with CsMYB75‐ or CsMYB86‐directed MYB–bHLH–WD40 (MBW) complexes. CsbZIP1–CsmiR858a, CsCOP1–CsbZIP1–CsPIF3, and BR signaling are involved in this stress‐modified CsMYBL2b and CsMYBL2a expression, which further regulate MBW activation of catechin and anthocyanin production.