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Purayannur S, Cano LM, Bowman MJ, Childs KL, Gent DH, Quesada-Ocampo LM. The Effector Repertoire of the Hop Downy Mildew Pathogen Pseudoperonospora humuli. Front Genet 2020; 11:910. [PMID: 32849854 PMCID: PMC7432248 DOI: 10.3389/fgene.2020.00910] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2020] [Accepted: 07/22/2020] [Indexed: 01/18/2023] Open
Abstract
Pseudoperonospora humuli is an obligate biotrophic oomycete that causes downy mildew (DM), one of the most destructive diseases of cultivated hop that can lead to 100% crop loss in susceptible cultivars. We used the published genome of P. humuli to predict the secretome and effectorome and analyze the transcriptome variation among diverse isolates and during infection of hop leaves. Mining the predicted coding genes of the sequenced isolate OR502AA of P. humuli revealed a secretome of 1,250 genes. We identified 296 RXLR and RXLR-like effector-encoding genes in the secretome. Among the predicted RXLRs, there were several WY-motif-containing effectors that lacked canonical RXLR domains. Transcriptome analysis of sporangia from 12 different isolates collected from various hop cultivars revealed 754 secreted proteins and 201 RXLR effectors that showed transcript evidence across all isolates with reads per kilobase million (RPKM) values > 0. RNA-seq analysis of OR502AA-infected hop leaf samples at different time points after infection revealed highly expressed effectors that may play a relevant role in pathogenicity. Quantitative RT-PCR analysis confirmed the differential expression of selected effectors. We identified a set of P. humuli core effectors that showed transcript evidence in all tested isolates and elevated expression during infection. These effectors are ideal candidates for functional analysis and effector-assisted breeding to develop DM resistant hop cultivars.
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Affiliation(s)
- Savithri Purayannur
- Department of Entomology and Plant Pathology, North Carolina State University, Raleigh, NC, United States
| | - Liliana M. Cano
- Department of Entomology and Plant Pathology, North Carolina State University, Raleigh, NC, United States
- Indian River Research and Education Center, Department of Plant Pathology, Institute of Food and Agricultural Sciences, University of Florida, Fort Pierce, FL, United States
| | - Megan J. Bowman
- Department of Plant Biology, Michigan State University, East Lansing, MI, United States
- Ball Horticultural Company, West Chicago, IL, United States
| | - Kevin L. Childs
- Department of Plant Biology, Michigan State University, East Lansing, MI, United States
| | - David H. Gent
- United States Department of Agriculture-Agricultural Research Service, Forage Seed and Cereal Research Unit, Oregon State University, Corvallis, OR, United States
| | - Lina M. Quesada-Ocampo
- Department of Entomology and Plant Pathology, North Carolina State University, Raleigh, NC, United States
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