Transcriptomic evidence for the control of soybean root isoflavonoid content by regulation of overlapping phenylpropanoid pathways

Citation

Dastmalchi, M., Chapman, P., Yu, J., Austin, R.S., Dhaubhadel, S. (2017). Transcriptomic evidence for the control of soybean root isoflavonoid content by regulation of overlapping phenylpropanoid pathways, 18(1), http://dx.doi.org/10.1186/s12864-016-3463-y

Plain language summary

Here we demonstrate that soybean cultivars that are resistance to root rot disease accumulate higher level of isoflavonoids compared to the susceptible cultivars. We show that coordinated regulation of genes involved in flavonoid metabolism could redirect flux into the isoflavonoid branch of the phenylpropanoid pathway. This could be implemented by reducing the competition for the flavanone substrate, altering downstream metabolism, or facilitating conjugation and/or sequestration of isoflavonoids. Additionally, we have identified several candidate genes that can help identify mechanisms to overcome the endogenous bottleneck to isoflavonoid production, facilitate biosynthesis in heterologous systems, and enhance crop resistance against pathogenic infections. The results presented in this manuscript are important findings because soybean isoflavonoids are phytoestrogens with significant biological activities in human health and nutrition as well as in plant pathogen interactions.

Abstract

Background: Isoflavonoids are a class of specialized metabolites found predominantly in legumes. They play a role in signaling for symbiosis with nitrogen-fixing bacteria and inhibiting pathogen infection. Results: A transcriptomic approach using soybean cultivars with high (Conrad and AC Colombe) and low (AC Glengarry and Pagoda) root isoflavonoid content was used to find elements that underlie this variation. Two genes, encoding the flavonoid-metabolizing enzymes, flavonoid 3'-hydroxylase (GmF3'H) and dihydroflavonol 4-reductase (GmDFR), had lower expression levels in high isoflavonoid cultivars. These enzymes compete with isoflavonoid biosynthetic enzymes for the important branch-point substrate naringenin and its derivatives. Differentially expressed genes, between the two sets of cultivars, encode transcription factors, transporters and enzymatic families of interest, such as oxidoreductases, hydrolases and transferases. In addition, genes annotated with stress and disease response were upregulated in high isoflavonoid cultivars. Conclusions: Coordinated regulation of genes involved in flavonoid metabolism could redirect flux into the isoflavonoid branch of the phenylpropanoid pathway, by reducing competition for the flavanone substrate. These candidate genes could help identify mechanisms to overcome the endogenous bottleneck to isoflavonoid production, facilitate biosynthesis in heterologous systems, and enhance crop resistance against pathogenic infections.

Publication date

2017-01-11