Powdery Mildew Induces Defense-Oriented Reprogramming of the Transcriptome in a Susceptible But Not in a Resistant Grapevine

Abstract

Grapevines exhibit a wide spectrum of resistance to the powdery mildew fungus (PM), Erysiphe necator (Schw.) Burr., but little is known about the transcriptional basis of the defense to PM. Our microscopic observations showed that PM produced less hyphal growth and induced more brown-colored epidermal cells on leaves of PM-resistant Vitis aestivalis 'Norton' than on leaves of PM-susceptible Vitis vinifera 'Cabernet sauvignon'. We found that endogenous salicylic acid levels were higher in V. aestivalis than in V. vinifera in the absence of the fungus and that salicylic acid levels increased in V. vinifera at 120 h postinoculation with PM. To test the hypothesis that gene expression differences would be apparent when V. aestivalis and V. vinifera were mounting a response to PM, we conducted a comprehensive Vitis GeneChip analysis. We examined the transcriptome at 0, 4, 8, 12, 24, and 48 h postinoculation with PM. We found only three PM-responsive transcripts in V. aestivalis and 625 in V. vinifera. There was a significant increase in the abundance of transcripts encoding ENHANCED DISEASE SUSCEPTIBILITY1, mitogen-activated protein kinase kinase, WRKY, PATHOGENESIS-RELATED1, PATHOGENESIS-RELATED10, and stilbene synthase in PM-infected V. vinifera, suggesting an induction of the basal defense response. The overall changes in the PM-responsive V. vinifera transcriptome also indicated a possible reprogramming of metabolism toward the increased synthesis of the secondary metabolites. These results suggested that resistance to PM in V. aestivalis was not associated with overall reprogramming of the transcriptome. However, PM induced defense-oriented transcriptional changes in V. vinifera.

Promoter Analysis of a Powdery Mildew Induced Vitis vinifera NAC Transcription Factor Gene

“…The powdery mildew regulated VvNAC36 transcription factor gene may have positive role in defense system against powdery mildew infection. As the previous microarray study indicated, the high expression of VvNAC36 transcription factor gene was only regulated by powdery mildew and not by exogenous salicylic acid treatment [14]. This study identified the responsible motif for regulation of this gene, the GT-1 box, which is regulated by elicitor not by salicylic acid.…”

“…For instance VvNAC18, VvNAC29, VvNAC37, VvNAC65 and VvNAC70 were expressed at high levels at inflorescence; VvNAC26 plays key roles in response to abiotic stress; in biotic stress response 7 VvNAC increased expression after virus-infection and 10 were up-regulated after Bois noir infection [1]. In addition 7 VvNAC transcription factor genes have been up regulated by powdery mildew elicitor at different levels in the given hour post infection (phi) [14]. Among these 7 transcription factor genes VvNAC36 has been significantly up regulated by powdery mildew infection.…”

Microbial biogeography of wine grapes is conditioned by cultivar, vintage, and climate

“…Relationships between grape variety and the abundance of yeast (35,36) and bacterial species (37) on berry surfaces have been documented previously on very limited scales, but not statistically demonstrated. Cultivar differences in growth habit and stress and invasion response (38) could explain how Vitis manages (or incurs) its grape-surface microbial ecosystems, explaining both the "normal" microbiota and cultivar-specific susceptibilities to disease pressures under different environments. Many of the observed patterns support this hypothesis.…”

Laser microdissection of Arabidopsis cells at the powdery mildew infection site reveals site-specific processes and regulators

“…3A and SI Appendix). Although a decrease in photosynthesis-associated gene expression had previously been observed in whole leaves in response to PM (4,7,11), our focus at the site of infection allowed us to identify a more extensive set of altered photosynthesis-related genes. It also eliminated potential complications associated with differential PM-induced impacts on photosynthesis at the site of infection compared with nearby or distal sites.…”