Identification of an attenuated barley stripe mosaic virus for the virus-induced gene silencing of pathogenesis-related wheat genes.

Leann M Buhrow,Michele C Loewen,Shawn M Clark

doi:10.1186/s13007-016-0112-z

Abstract

Background Virus-induced gene silencing (VIGS) has become an emerging technology for the rapid, efficient functional genomic screening of monocot and dicot species. The barley stripe mosaic virus (BSMV) has been described as an effective VIGS vehicle for the evaluation of genes involved in wheat and barley phytopathogenesis; however, these studies have been obscured by BSMV-induced phenotypes and defense responses. The utility of BSMV VIGS may be improved using a BSMV genetic background which is more tolerable to the host plant especially upon secondary infection of highly aggressive, necrotrophic pathogens such as Fusarium graminearum.ResultsBSMV-induced VIGS in Triticum aestivum (bread wheat) cv. ‘Fielder’ was assessed for the study of wheat genes putatively related to Fusarium Head Blight (FHB), the necrotrophism of wheat and other cereals by F. graminearum. Due to the lack of ‘Fielder’ spike viability and increased accumulation of Fusarium-derived deoxynivalenol contamination upon co-infection of BSMV and FHB, an attenuated BSMV construct was generated by the addition of a glycine-rich, C-terminal peptide to the BSMV γ b protein. This attenuated BSMV effectively silenced target wheat genes while limiting disease severity, deoxynivalenol contamination, and yield loss upon Fusarium co-infection compared to the original BSMV construct. The attenuated BSMV-infected tissue exhibited reduced abscisic, jasmonic, and salicylic acid defense phytohormone accumulation upon secondary Fusarium infection. Finally, the attenuated BSMV was used to investigate the role of the salicylic acid-responsive pathogenesis-related 1 in response to FHB.ConclusionsThe use of an attenuated BSMV may be advantageous in characterizing wheat genes involved in phytopathogenesis, including Fusarium necrotrophism, where minimal viral background effects on defense are required. Additionally, the attenuated BSMV elicits reduced defense hormone accumulation, suggesting that this genotype may have applications for the investigation of phytohormone-related signaling, developmental responses, and pathogen defense.Electronic supplementary materialThe online version of this article (doi:10.1186/s13007-016-0112-z) contains supplementary material, which is available to authorized users.

Highlights

Virus-induced gene silencing (VIGS) has become an emerging technology for the rapid, efficient functional genomic screening of monocot and dicot species
Fielder was infected during booting with barley stripe mosaic virus (BSMV) encoding no VIGS-targeted gene fragment (BSMV:00) or BSMV encoding a 200 bp non-VIGS-targeted GFP fragment (BSMV:GFP)
The co-infection of BSMV and Fusarium head blight (FHB) resulted in a dramatic increase in spike necrosis and Fusarium–derived DON contamination in ‘Fielder’ spikes (Fig. 1a–c)

Summary

Introduction

Virus-induced gene silencing (VIGS) has become an emerging technology for the rapid, efficient functional genomic screening of monocot and dicot species. BSMV VIGS has been shown to be an effective tool in the functional genomics characterization of monocot genes involved in fungal pathogenesis including leaf and stem rust, powdery mildew, and wheat blast [9,10,11]. These studies have been complicated by the phenotypic and defense responses induced upon BSMV infection alone [1, 9, 10]. Abscisic acid (ABA) and auxin (IAA) metabolite applications has been shown to increase and decreases FHB disease symptoms in susceptible cultivars, respectively [16, 17]

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Discussion

Conclusion