Exogenous indole-3-acetic acid and trans-zeatin riboside synergistically induced CsHD-ZIP35 and CsMYB125 to promote biosynthesis of epigallocatechin gallate in tea plants (Camellia sinensis)

As the most abundant catechin in Camellia sinensis , epigallocatechin gallate (EGCG) is closely related to the nutritional quality and health value of tea, and clarifying its biosynthesis regulatory network is crucial for directional improvement of tea quality. However, the regulatory mechanism by which plant hormones regulate EGCG biosynthesis in tea plants remains incompletely understood. This study was intended to explore the regulatory effects of the synergistic interaction between indole-3-acetic acid (IAA) and trans-zeatin riboside (tZR) on EGCG biosynthesis in young tea shoots. The results demonstrated that exogenous IAA-tZR treatment significantly increased the EGCG content in young tea shoots by 12.79% compared to the control. Integrated metabolomic and transcriptomic analyses, together with antisense oligodeoxynucleotide (asODN)-mediated gene silencing, revealed that the auxin signal factor CsARF5 and the cytokinin signal factor CsB-ARR1 act as key synergistic regulators of the two hormone pathways. TFs CsHD-ZIP35 and CsMYB12 5 are the synergistic sites of two hormone signal factors, and CsSCPL25 is an important downstream structural gene targeted by these transcription factors. Collectively, exogenous IAA-tZR treatment promoted the biosynthesis of EGCG in tea shoots by regulating the expression of CsSCPL25 through CsHD-ZIP35 and CsMYB125 . This study provides new insights into the synergistic regulation of auxin and cytokinin signaling pathways on EGCG biosynthesis in tea plants.