MYB transcription factor PdMYB118 directly interacts with bHLH transcription factor PdTT8 to regulate wound-induced anthocyanin biosynthesis in poplar

Abstract

Background: R2R3-MYB transcription factors (TFs) play important roles in plant growth and development, and response to biotic and abiotic stresses. However, their regulatory mechanisms in wound-induced anthocyanin biosynthesis in woody plants are largely unknown. Results: In this work, we report that expression of anthocyanin biosynthesis genes (ABGs) were activated by PdMYB118, a MYB TF encoding gene from Populus deltoids, and the activation of PdMYB118 was significantly enhanced by PdTT8, a bHLH protein, through its direct interaction with PdMYB118. PdMYB118 and some ABGs were evidently induced by wound induction and methyl jasmonate (MeJA) treatment. Overexpression of PdMYB118 promoted anthocyanin accumulation in transgenic poplar upon wound induction. Furthermore, a poplar JASMONATE ZIM-domain (JAZ) protein, PtrJAZ1, repressed the transcriptional function of PdMYB118/PdTT8 complex by binding to PdTT8, and wound stimulated the biosynthesis of jasmonic acid (JA) and the degradation of PtrJAZ1. Conclusions: Based on these observations, we proposed that PtrJAZ1 degradation triggered the expression of ABGs, leading to increased biosynthesis of anthocyanins in the wounded leaves of transgenic poplar. Therefore, our findings not only illustrate the crucial role of PdMYB118 in wound-induced anthocyanin biosynthesis in poplar, but also provide a molecular basis for the genetic engineering of colorful tree species.

Current Understanding of bHLH Transcription Factors in Plant Abiotic Stress Tolerance

“…PIF1 degradation is related to phyB activity [ 21 ]. In wounded poplar ( Populus deltoids ) plants, the biosynthesis of anthocyanin, a pigment important in plant defense, is induced via a pathway regulated by PdTT8 (a bHLH transcription factor) together with PdMYB118 (a MYB transcription factor) [ 22 ]. Additionally, bHLH TFs play important roles in anthocyanin accumulation in Arabidopsis, which is associated with the jasmonate (JA)-regulated plant defense pathway [ 23 ].…”

Genome-wide identification and characterization of PdbHLH transcription factors related to anthocyanin biosynthesis in colored-leaf poplar (Populus deltoids)

“…The Lc protein was the first reported bHLH TFs in maize, which can be involved in the anthocyanin biosynthesis through regulating at least 2 structural genes [ 20 ]. Moreover, several bHLH TFs related to anthocyanin biosynthesis were identified and further characterized in other plants, such as Arabidopsis ( AtEGL3 , AtGL3 , and AtTT8 ) [ 21 ], V. vinifera ( VvMYCA1 ) [ 22 ], N. tabacum ( NtAn1 and NtAn2 ) [ 23 ], M. domestica ( MdbHLH3 and MdMYC2 ) [ 24 , 25 ] and poplar ( PdTT8 ) [ 26 ]. In poplar, PdTT8 directly interacts with PdMYB118 TF to regulate wound-induced anthocyanin biosynthesis [ 26 ].…”

“…Moreover, several bHLH TFs related to anthocyanin biosynthesis were identified and further characterized in other plants, such as Arabidopsis ( AtEGL3 , AtGL3 , and AtTT8 ) [ 21 ], V. vinifera ( VvMYCA1 ) [ 22 ], N. tabacum ( NtAn1 and NtAn2 ) [ 23 ], M. domestica ( MdbHLH3 and MdMYC2 ) [ 24 , 25 ] and poplar ( PdTT8 ) [ 26 ]. In poplar, PdTT8 directly interacts with PdMYB118 TF to regulate wound-induced anthocyanin biosynthesis [ 26 ]. However, several questions are still needed to be explored.…”

Ectopic Expression of Production of Anthocyanin Pigment 1 (PAP1) Improves the Antioxidant and Anti-Melanogenic Properties of Ginseng (Panax ginseng C.A. Meyer) Hairy Roots

“…Another possible approach to improve anthocyanin production in plants is the overexpression of transcription factors known to activate anthocyanin biosynthesis genes. At the transcriptional level, anthocyanin biosynthesis is known to be tightly regulated by R2R3-MYB, MYC-like basic helix-loop-helix (bHLH), and WD40-repeat transcription factors, as well as by their coordinated interactions (MYB-bHLH-WD40 regulatory complexes) [ 10 , 11 ]. Among the three proteins that form the MBW complex, R2R3-MYB activates transcription of the anthocyanin biosynthetic genes via direct binding to specific DNA sequences, resulting in a sharp anthocyanin accumulation [ 12 , 13 , 14 ].…”