DOI: 10.3724/SP.J.1006.2018.00185

Acta Agronomica Sinica (作物学报) 2018/44:2 PP.185-196

An R2R3-MYB Transcription Factor GmMYB184 Regulates Soybean Isoflavone Synthesis

Isoflavones comprise a group of secondary metabolites produced almost exclusively by plants in the legume family, including soybean[Glycine max (L.) Merr.]. They play vital roles in plant defense and have many beneficial effects on human health. Isoflavone content is controlled by multiple genes and complex metabolic networks. The modification of certain structural genes in the isoflavone pathway by genetic engineering has been unable to significantly improve isoflavone content. The identification and application of transcription factors specific to the isoflavone pathway may effectively resolve this problem. An R2R3-type transcription factor related to isoflavone content, GmMYB184, was cloned and its function was identified. Subcellular localization study confirmed the nuclear localization of GmMYB184. The expression profile of GmMYB184 was similar to that of IFS2 (isoflavone synthase 2), which was consistent with the isoflavone accumulation pattern. In addition, GmMYB184 and IFS2 mainly expressed in roots and mature seeds, and the expression level increased by seeds maturing. Glutathione (GSH) induction expression analysis showed that both GmMYB184 and IFS2 were induced by GSH, indicating they could be involved in similar biological processes. To examine whether GmMYB184 could regulate the expression of isoflavone biosynthesis-related genes, a dual luciferase reporter gene assay was performed, showing that GmMYB184 could increase the expression of IFS2 and CHS8 (chalcone synthase 8) to five and seven folds, respectively. Finally, to further verify the function of GmMYB184 during isoflavone biosynthesis, we constructed and then transformed overexpression vector and RNAi vector for GmMYB184 to soybean hairy roots respectively. RNAi silencing of GmMYB184 in hairy roots resulted in reduction of isoflavones. However, overexpression of GmMYB184 was not sufficient to increase isoflavone contents in hairy roots. Taken together, these results provide a theoretical foundation for the molecule mechanism explanation and genetic improvement of isoflavone content in soybean.

Key words:soybean,isoflavone content,GmMYB184,transcription factor,functional identification

ReleaseDate:2018-03-08 10:13:39

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