Phenylalanine ammonia-lyase2.1 contributes to the soybean response towards Phytophthora sojae infection

Chuanzhong Zhang,Dongmei Li,Ninghui Li,Qun Cheng,Feng Zhang,Sujie Fan,Liangyu Jiang,Shuzhen Zhang,Pengfei Xu,Lidong Dong,Xiaofei Yan,Junjiang Wu,Dongyue Qi,Xin Wang

doi:10.1038/s41598-017-07832-2

Abstract

Phytophthora root and stem rot of soybean [Glycine max (L.) Merr.] caused by Phytophthora sojae is a destructive disease worldwide. Phenylalanine ammonia-lyase (PAL) is one of the most extensively studied enzymes related to plant responses to biotic and abiotic stresses. However, the molecular mechanism of PAL in soybean in response to P. sojae is largely unclear. Here, we characterize a novel member of the soybean PAL gene family, GmPAL2.1, which is significantly induced by P. sojae. Overexpression and RNA interference analysis demonstrates that GmPAL2.1 enhances resistance to P. sojae in transgenic soybean plants. In addition, the PAL activity in GmPAL2.1-OX transgenic soybean is significantly higher than that of non-transgenic plants after infection with P. sojae, while that in GmPAL2.1-RNAi soybean plants is lower. Further analyses show that the daidzein, genistein and salicylic acid (SA) levels and the relative content of glyceollins are markedly increased in GmPAL2.1-OX transgenic soybean. Taken together, these results suggest the important role of GmPAL2.1 functioning as a positive regulator in the soybean response to P. sojae infection, possibly by enhancing the content of glyceollins, daidzein, genistein and SA.

Highlights

Phytophthora root and stem rot of soybean [Glycine max (L.) Merr.] caused by Phytophthora sojae is a destructive disease worldwide
A cDNA library enriched for mRNAs encoding expressed sequence tag (EST) that were increased in abundance during infection with P. sojae was constructed by suppression subtractive hybridization from leaf tissues of the highly resistant soybean cultivar ‘Suinong 10’, and an EST homologous to a phenylalanine ammonia-lyase from Lotus japonicus was identified to be upregulated by microarray and real-time PCR46
Sequence analysis suggests that the full length of GmPAL2.1 is 2284 bp and contains an open reading frame (ORF) encoding a polypeptide of 717 amino acids (Supplementary Fig. 1), with a predicted molecular mass of 78.116 kDa and a theoretic isoelectric point of 5.83

Summary

Introduction

Phytophthora root and stem rot of soybean [Glycine max (L.) Merr.] caused by Phytophthora sojae is a destructive disease worldwide. Glyceollins protect plant tissues from environmental challenges, possibly by reducing the oxidative damage induced by stress factors. These compounds have significant cellular anti-oxidative activities[10,11,12]. A cDNA library enriched for mRNAs encoding ESTs that were increased in abundance during infection with P. sojae was constructed by suppression subtractive hybridization from leaf tissues of the highly resistant soybean cultivar ‘Suinong 10’, and an EST homologous to a phenylalanine ammonia-lyase from Lotus japonicus was identified to be upregulated by microarray and real-time PCR46. We report insights into the function of a PAL gene in soybean, GmPAL2.1, in the defense response against P. sojae

Methods

Results

Conclusion