Chen L, Yang H, Fang Y, Guo W, Chen H, Zhang X, Dai W, Chen S, Hao Q, Yuan S, Zhang C, Huang Y, Shan Z, Yang Z, Qiu D, Liu X, Tran LP, Zhou X, Cao D.

Plant Biotechnol J. 2021 Apr;19(4):702-716.

Abstract

MYB transcription factors (TFs) have been reported to regulate the biosynthesis of secondary metabolites, as well as to mediate plant adaption to abiotic stresses, including drought. However, the roles of MYB TFs in regulating plant architecture and yield potential remain poorly understood. Here, we studied the roles of the dehydration-inducible GmMYB14 gene in regulating plant architecture, high-density yield and drought tolerance through the brassinosteroid (BR) pathway in soybean. GmMYB14 was shown to localize to nucleus and has a transactivation activity. Stable GmMYB14-overexpressing (GmMYB14-OX) transgenic soybean plants displayed a semi-dwarfism and compact plant architecture associated with decreased cell size, resulting in a decrease in plant height, internode length, leaf area, leaf petiole length and leaf petiole angle, and improved yield in high density under field conditions. Results of the transcriptome sequencing suggested the involvement of BRs in regulating GmMYB14-OX plant architecture. Indeed, GmMYB14-OX plants showed reduced endogenous BR contents, while exogenous application of brassinolide could partly rescue the phenotype of GmMYB14-OX plants. Furthermore, GmMYB14 was shown to directly bind to the promoter of GmBEN1 and up-regulate its expression, leading to reduced BR content in GmMYB14-OX plants. GmMYB14-OX plants also displayed improved drought tolerance under field conditions. GmBEN1 expression was also up-regulated in the leaves of GmMYB14-OX plants under polyethylene glycol treatment, indicating that the GmBEN1-mediated reduction in BR level under stress also contributed to drought/osmotic stress tolerance of the transgenic plants. Our findings provided a strategy for stably increasing high-density yield and drought tolerance in soybean using a single TF-encoding gene.

See: https://pubmed.ncbi.nlm.nih.gov/33098207/

Figure 1

Phylogenetic relationship, gene expression analysis, localization and transactivation assay of the GmMYB14 transcription factor. (a) Phylogenetic analysis of GmMYB14 and its orthologs in soybean (Glyma.03G163100, Glyma.20G209700, Glyma.10G180800, Glyma.10G006600 and Glyma.02G005600), Arabidopsis thaliana (AtMYB13, AtMYB14 and AtMYB15) and other MYB proteins in soybean (GmMYB181), Capsicum annuum (CaBlind) and Solanum lycopersicum (SlBlind) involved in regulating plant architecture. (b) Expression of GmMYB14 in different organs. Relative expression levels were normalized to the expression level of GmActin. (c) Expression of GmMYB14 in leaves after treatment with different concentrations of brassinolide (BL) for 3 h (n = 3 biological repeats). (d) Expression of GmMYB14 in leaf samples after treatment with 5 μM BL for different time periods (n = 3 biological repeats). (e) GmMYB14 is localized to the nucleus in tobacco epidermal cells. The fluorescences of GmMYB14‐GFP and GFP (negative control) were visualized with a high‐resolution laser confocal microscope at 488 nm. BF, bright field; mCherry, FIBRILLARIN2‐mCherry nucleolar marker; bar = 20 µm. (f) Transactivation assay of GmMYB14 in yeast cells harbouring ‘pGBKT7:GmMYB14’ construct. Transformed yeast cells harbouring ‘pGBKT7’ vector were used as a negative control. In each panel, the yeast cells harbouring the indicated plasmid combinations were grown on either the nonselective (e.g. SD/‐Trp) or selective (e.g. SD/‐Trp/‐His/‐Ade medium containing X‐α‐Gal) medium that allowed the α‐galactosidase activity assay (X‐α‐Gal staining). Decreasing cell densities in the dilution series are illustrated by 10⁰, 10⁻¹and 10⁻². Statistically significant difference between each BL treatment and mock is marked with asterisk(s) (*P < 0.05; **P < 0.01; and ***P < 0.001; Student's t‐test).