Soybean GmMYB73 promotes lipid accumulation in transgenic plants

Yun-Feng Liu,Guang-Hou Shui,Shou-Yi Chen,Biao Ma,Qing-Tian Li,Sin-Man Lam,Wan-Ke Zhang,Xiang Lu,Qing Lin,Qing-Xin Song,Wei-Guang Du,Wei-Qun Man,Jin-Song Zhang

doi:10.1186/1471-2229-14-73

Abstract

BackgroundSoybean is one of the most important oil crops. The regulatory genes involved in oil accumulation are largely unclear. We initiated studies to identify genes that regulate this process.ResultsOne MYB-type gene GmMYB73 was found to display differential expression in soybean seeds of different developing stages by microarray analysis and was further investigated for its functions in lipid accumulation. GmMYB73 is a small protein with single MYB repeat and has similarity to CPC-like MYB proteins from Arabidopsis. GmMYB73 interacted with GL3 and EGL3, and then suppressed GL2, a negative regulator of oil accumulation. GmMYB73 overexpression enhanced lipid contents in both seeds and leaves of transgenic Arabidopsis plants. Seed length and thousand-seed weight were also promoted. GmMYB73 introduction into the Arabidopsis try cpc double mutant rescued the total lipids, seed size and thousand-seed weight. GmMYB73 also elevated lipid levels in seeds and leaves of transgenic Lotus, and in transgenic hairy roots of soybean plants. GmMYB73 promoted PLDα1 expression, whose promoter can be bound and inhibited by GL2. PLDα1 mutation reduced triacylglycerol levels mildly in seeds but significantly in leaves of Arabidopsis plants.ConclusionsGmMYB73 may reduce GL2, and then release GL2-inhibited PLDα1 expression for lipid accumulation. Manipulation of GmMYB73 may potentially improve oil production in legume crop plants.

Highlights

Soybean is one of the most important oil crops
GmMYB73-transgenic hairy roots (GmMYB73) gene expression The developing soybean seeds were divided into seven stages from pollination to mature seeds, and the relative seed weigh at each stage ranged from 4% to 96% when compared to the full size seeds without desiccation (Figure 1a, GmMYB73 binds to GL3 and EGL3 and inhibits GL2 expression In Arabidopsis, CPC-like R3 MYB proteins (e.g. TRY and CPC) are repressors for transcriptional activator and compete with GL1 for binding to GL3 and EGL3, both are bHLH factors [46,47]
GUS activity was quantified in leaves, hypocotyls and roots of above transgenic plants, and the levels were consistent with the GUS staining results (Figure 2c, d, e). These results indicate that GmMYB73 negatively regulates trichome formation by interacting with GL3 and EGL3 to repress GL2 transcription in transgenic Arabidopsis plants

Summary

Introduction

Soybean is one of the most important oil crops. The regulatory genes involved in oil accumulation are largely unclear. We initiated studies to identify genes that regulate this process. As an important oil crop, soybean provides oils for edible, industrial and new energy uses to meet the increasing demand [1,2]. The oil content in soybean seeds generally ranges from 13% to 22% in various soybean cultivars, and is relatively low compared to most other oilseed crops [3]. High content of oil in soybean seeds is desirable and has been a major goal of breeding and genetic engineering. Fatty acids are stored as triacylglycerols (TAGs) in seeds [4,5]. The regulation of TAG metabolism involves two mechanisms.

Methods

Results

Conclusion