Overexpression of Soybean Isoflavone Reductase (GmIFR) Enhances Resistance to Phytophthora sojae in Soybean.

Qun Cheng,Sujie Fan,Ninghui Li,Liangyu Jiang,Dayong Zhang,Lidong Dong,Pengfei Xu,Xin Wang,Xin Wang,Shuzhen Zhang,Ninghui Li

doi:10.3389/fpls.2015.01024

Abstract

Isoflavone reductase (IFR) is an enzyme involved in the biosynthetic pathway of isoflavonoid phytoalexin in plants. IFRs are unique to the plant kingdom and are considered to have crucial roles in plant response to various biotic and abiotic environmental stresses. Here, we report the characterization of a novel member of the soybean isoflavone reductase gene family GmIFR. Overexpression of GmIFR transgenic soybean exhibited enhanced resistance to Phytophthora sojae. Following stress treatments, GmIFR was significantly induced by P. sojae, ethephon (ET), abscisic acid (placeCityABA), salicylic acid (SA). It is located in the cytoplasm when transiently expressed in soybean protoplasts. The daidzein levels reduced greatly for the seeds of transgenic plants, while the relative content of glyceollins in transgenic plants was significantly higher than that of non-transgenic plants. Furthermore, we found that the relative expression levels of reactive oxygen species (ROS) of transgenic soybean plants were significantly lower than those of non-transgenic plants after incubation with P. sojae, suggesting an important role of GmIFR might function as an antioxidant to reduce ROS in soybean. The enzyme activity assay suggested that GmIFR has isoflavone reductase activity.

Highlights

A major response of soybean to attack by fungal pathogens and oomycetes is production of isoflavonoid phytoalexin glyceollins (Partridge and Keen, 1977; Yoshikawa et al, 1978; Banks and Dewick, 1983; Ng et al, 2011; Kim et al, 2012)
Alignment and phylogenetic tree analysis of leguminous plants sequences revealed that GmIFR has 44–94% identity for overall amino acid sequence to Phaseolus vulgaris PvIFR, Cicer arietinum CaIFR, Medicago truncatula MtIRF, Lotus japonicus LjIFR, Glycine soja GsIFR, Medicago sativa MsIFR, Pisum sativum PsIFR (Supplementary Figure S2B)
The analysis of homologs of GmIFR in the soybean genome, based on data obtained from the Phytozome database, indicated that the two genes were clustered on two linkage groups, namely one each on Gm 01 and Gm 09 and had three introns

Summary

Introduction

A major response of soybean to attack by fungal pathogens and oomycetes is production of isoflavonoid phytoalexin glyceollins (Partridge and Keen, 1977; Yoshikawa et al, 1978; Banks and Dewick, 1983; Ng et al, 2011; Kim et al, 2012) They are valuable secondary metabolities produced primarily in leguminous plants and are rarely found in other plant families (Wang et al, 2006; Kim et al, 2010b), and are synthesized by the isoflavonoid branch of the central phenylopropanoid pathway (Ng et al, 2011). IFR is a monomeric, cytosolic reductase, and the enzyme can use 2′-hydroxydaidzein, 2′-hydroxyformononetin, and 2′-hydroxygenistein as substrates in soybean (Wang et al, 2006)

Methods

Results

Conclusion