Regulation of plant immunity through modulation of phytoalexin synthesis.

Olga V Zernova,Jack M Widholm,Curtis B Hill,Glen L Hartman,Michelle L Pawlowski,Vera V Lozovaya,Anatoli V Lygin

doi:10.3390/molecules19067480

Olga V Zernova, Jack M Widholm + Show 5 more

Open Access

https://doi.org/10.3390/molecules19067480

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Abstract

Soybean hairy roots transformed with the resveratrol synthase and resveratrol oxymethyl transferase genes driven by constitutive Arabidopsis actin and CsVMV promoters were characterized. Transformed hairy roots accumulated glycoside conjugates of the stilbenic compound resveratrol and the related compound pterostilbene, which are normally not synthesized by soybean plants. Expression of the non-native stilbenic phytoalexin synthesis in soybean hairy roots increased their resistance to the soybean pathogen Rhizoctonia solani. The expression of the AhRS3 gene resulted in 20% to 50% decreased root necrosis compared to that of untransformed hairy roots. The expression of two genes, the AhRS3 and ROMT, required for pterostilbene synthesis in soybean, resulted in significantly lower root necrosis (ranging from 0% to 7%) in transgenic roots than in untransformed hairy roots that had about 84% necrosis. Overexpression of the soybean prenyltransferase (dimethylallyltransferase) G4DT gene in soybean hairy roots increased.

Highlights

Diseases and pests can keep soybean grain producers from achieving maximum productivity
Our previous studies showed that transgenic modulation of soybean plant potential to accumulate glyceollin in response to pathogen attacks increased soybean disease resistance, with higher resistance found in plants with elevated glyceollin synthesis [16,19,20,21,22,23]
In this paper we provide molecular and biochemical characteristics of soybean hairy roots expressing resveratrol synthase and resveratrol oxymethyl transferase under control of constitutive promoters which are capable of producing different levels of stilbenic compounds that are normally not synthesized by soybean, and describe the effects of the non-native phytoalexin expression on severity of infection caused by the soybean generalist fungus, Rhizoctonia solani

Summary

Introduction

Diseases and pests can keep soybean grain producers from achieving maximum productivity. Expression of the non-native phytoalexin synthesis in crop plants could increase plant immunity and resistance to pests and diseases because host pathogens may have low capability to detoxify non-native phytoalexins, which reduce the rate of colonization until other parts of innate plant defense are activated to maximum levels, such as the production of antimicrobial reactive oxygen species. The expression of the STS genes in these studies led to increased STS activity and accumulation of resveratrol glycoside conjugates in transgenic plants and, importantly, resulted in increased plant resistance to fungal pathogens [31]. Transgenic expression of stilbene synthase from grape into tobacco, tomato, and alfalfa resulted in accumulation of conjugates of the nonnative phytoalexin resveratrol, and correspondingly, increased resistance to Botrytis cinerea [10], to Phytophthora infestans [27] and to Phoma medicaginis [29]. We describe how overexpression of the prenyltransferase (dimethylallyltransferase) G4DT gene, responsible for the key prenylation reaction in the glyceollin synthesis [37], affects the capacity of hairy roots to accumulate native phytoalexin glyceollin in response to fungal infection

Expression of Non-Native Stilbenoid Phytoalexins in Soybean Hairy Roots

Genetic Modification of Soybean Hairy Roots

Molecular Analysis

Analysis of Phenylpropanoids in Soybean Tissue

Evaluation of Fungal Colonization of Hairy Root Cultures

Conclusions