AUTHOR=Teng Zhiyan , Zheng Weiwei , Yu Youjian , Hong Seung-Beom , Zhu Zhujun , Zang Yunxiang 

TITLE=Effects of BrMYC2/3/4 on Plant Development, Glucosinolate Metabolism, and Sclerotinia sclerotiorum Resistance in Transgenic Arabidopsis thaliana

JOURNAL=Frontiers in Plant Science

VOLUME=12

YEAR=2021

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2021.707054

DOI=10.3389/fpls.2021.707054

ISSN=1664-462X

ABSTRACT=<p>MYC2/3/4, known as a basic helix–loop–helix (bHLH) transcription factor, directly activate the genes involved in diverse plant development and secondary metabolites biosynthesis. In this study, we identified and cloned five <italic>MYC</italic> paralogs (<italic>BrMYC2</italic>/<italic>3-1</italic>/<italic>3-2</italic>/<italic>4-1</italic>/<italic>4-2</italic>) from Chinese cabbage (<italic>Brassica rapa</italic> ssp. <italic>pekinensis</italic>). <italic>In-silico</italic> analyses for the physicochemical properties suggested that BrMYC2/3-1/3-2/4-2/4-3 are unstable hydrophobic and acidic proteins, while BrMYC4-1 is an unstable hydrophobic and basic protein. BrMYC2/3/4 belong to the bHLH superfamily and are closely related to AthMYC2/3/4 orthologs that mediate the regulation of various secondary metabolites. It was demonstrated that BrMYC2/3/4-GFP fusion protein localized in the nucleus and expression levels of five <italic>BrMYC2/3/4</italic> homologous genes all elevated relative to control (Ctrl). When expressed in <italic>Arabidopsis</italic> under the control of 35S promoter, each of the <italic>BrMYC2/3-1/3-2/4-1/4-2</italic> transgenes differentially influenced root and shoot elongation, vegetative phase change, flowering time, plant height and tiller number after flowering, and seed production. Despite the variation of phenotypes between the transgenic lines, all the lines except for <italic>BrMYC4-2</italic> exhibited shorter seed length, less seed weight, higher accumulation of glucosinolates (GSs), and resistance to <italic>Sclerotinia sclerotiorum</italic> than Ctrl. Notably, <italic>BrMYC2</italic> overexpression (OE) line significantly reduced the lengths of root and hypocotyl, seed length, and weight, along with faster bolting time and strikingly higher accumulation of total GSs. Accumulation of GSs at the highest levels in the <italic>BrMYC2</italic><sup><italic>OE</italic></sup> line conferred the highest resistance to <italic>S. sclerotiorum</italic>. Unlike <italic>BrMYC3</italic><sup><italic>OE</italic></sup> and <italic>BrMYC4</italic><sup><italic>OE</italic></sup>, <italic>BrMYC2</italic><sup><italic>OE</italic></sup> stimulated the growth of plant height after fluorescence. The results of this study point to the <italic>BrMYC2</italic> overexpression that may provide a beneficial effect on plant growth and development <italic>via</italic> plant resistance to the fungal pathogen.</p>