A Medicago truncatula ABCG transporter modulates the level of isoflavonoids

Abstract

Full size ABCG transporters have been proposed to be implicated in the active transmembrane traffic of various secondary metabolites. Despite the importance of ABCG-based transport for plant-environment interactions, these proteins are still poorly characterised in legumes. The functional characterisation of, recently identified, Medicago ABCG10 was conducted by gene expression analyses, protein localization, as well as metabolites quantification. Biological assays were performed with control and MtABCG10-silenced material. The MtABCG10 mRNA accumulated upon the application of fungal oligosaccharides on plant roots. Spatial expression pattern analysis with a reporter gene revealed that the MtABCG10 promoter is active mostly within the vascular tissues in various organs. The corresponding protein is located in the plasma membrane. Silencing of MtABCG10 in hairy roots resulted in lower accumulation of the phenylpropanoid pathway-derived phytoalexin and its precursors. In addition, we observed that MtABCG10-silenced composite plants are more susceptible to infection with Fusarium oxysporum. Based upon the presented data, we propose that the MtABCG10 is a modulator of isoflavonoid levels during the defence response associated with de novo synthesis of Medicago phytoalexin.