The MIR-Domain of PbbHLH2 Is Involved in Regulation of the Anthocyanin Biosynthetic Pathway in "Red Zaosu" (PyrusBretschneideri Rehd.) Pear Fruit.

Xieyu Li,Zhigang Wang,Fangxin Xiang,Lingfei Xu,Wei Han,Rui Zhai,Chengquan Yang,Bingqing Qie

doi:10.3390/ijms22063026

Xieyu Li, Zhigang Wang + Show 6 more

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https://doi.org/10.3390/ijms22063026

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Abstract

The N-terminal of Myc-like basic helix-loop-helix transcription factors (bHLH TFs) contains an interaction domain, namely the MYB-interacting region (MIR), which interacts with the R2R3-MYB proteins to regulate genes involved in the anthocyanin biosynthetic pathway. However, the functions of MIR-domain bHLHs in this pathway are not fully understood. In this study, PbbHLH2 containing the MIR-domain was identified and its function investigated. The overexpression of PbbHLH2 in ”Zaosu” pear peel increased the anthocyanin content and the expression levels of late biosynthetic genes. Bimolecular fluorescence complementation showed that PbbHLH2 interacted with R2R3-MYB TFs PbMYB9, 10, and 10b in onion epidermal cells and confirmed that MIR-domain plays important roles in the interaction between the MIR-domain bHLH and R2R3-MYB TFs. Moreover, PbbHLH2 bound and activated the dihydroflavonol reductase promoter in yeast one-hybrid (Y1H) and dual-luciferase assays. Taken together these results suggested that the MIR domain of PbbHLH2 regulated anthocyanin biosynthesis in pear fruit peel.

Highlights

IntroductionAnthocyanins play important roles in plant growth and development, as well as resistance to stresses, such as oxidation [4], light [4,5], and cold [6,7,8]
We showed that the MYB-interacting region (MIR)-domain of PbbHLH2 protein interacts with PbMYB9, 10, and 10b, which are activators in the anthocyanin biosynthetic pathway
Our results showed that the PbbHLH2 interacts with PbMYB9, 10, and 10b through the MIR-domain to form a transcription complex in pear fruit peel

Summary

Introduction

Anthocyanins play important roles in plant growth and development, as well as resistance to stresses, such as oxidation [4], light [4,5], and cold [6,7,8]. Anthocyanin is involved in defending against pathogens [9] and attracting pollinators and seed dispersers [10]. They are beneficial to human health [11,12,13]. Anthocyanins play important roles in the prevention of cardiovascular and nervous system diseases [3,20]

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