Abstract
Take-all, which is caused by the fungal pathogen, Gaeumannomyces graminis var. tritici (Ggt), is an important soil-borne root rot disease of wheat occurring worldwide. However, the genetic basis of Ggt pathogenicity remains unclear. In this study, transcriptome sequencing for Ggt in axenic culture and Ggt-infected wheat roots was performed using Illumina paired-end sequencing. Approximately 2.62 and 7.76 Gb of clean reads were obtained, and 87% and 63% of the total reads were mapped to the Ggt genome for RNA extracted from Ggt in culture and infected roots, respectively. A total of 3,258 differentially expressed genes (DEGs) were identified with 2,107 (65%) being 2-fold up-regulated and 1,151 (35%) being 2-fold down-regulated between Ggt in culture and Ggt in infected wheat roots. Annotation of these DEGs revealed that many were associated with possible Ggt pathogenicity factors, such as genes for guanine nucleotide-binding protein alpha-2 subunit, cellulase, pectinase, xylanase, glucosidase, aspartic protease and gentisate 1, 2-dioxygenase. Twelve DEGs were analyzed for expression by qRT-PCR, and could be generally divided into those with high expression only early in infection, only late in infection and those that gradually increasing expression over time as root rot developed. This indicates that these possible pathogenicity factors may play roles during different stages of the interaction, such as signaling, plant cell wall degradation and responses to plant defense compounds. This is the first study to compare the transcriptomes of Ggt growing saprophytically in axenic cultures to it growing parasitically in infected wheat roots. As a result, new candidate pathogenicity factors have been identified, which can be further examined by gene knock-outs and other methods to assess their true role in the ability of Ggt to infect roots.
Highlights
Global wheat production is severely affected by take-all, a major fungal disease that is caused by Gaeumannomyces graminis var. tritici (Ggt), which can lead to yield losses of up to 40%60% [1]
RNA-seq expression profiling of Ggt was performed under two conditions: Ggt cultured in potato dextrose broth (PDB) and symptomatic Ggt-infected wheat roots
This study is the first to analyze the transcriptome of Ggt and infected wheat root using Illumina platform
Summary
Global wheat production is severely affected by take-all, a major fungal disease that is caused by Gaeumannomyces graminis var. tritici (Ggt), which can lead to yield losses of up to 40%60% [1]. Global wheat production is severely affected by take-all, a major fungal disease that is caused by Gaeumannomyces graminis var. Tritici (Ggt), which can lead to yield losses of up to 40%60% [1]. Ggt is a necrotrophic pathogen infecting wheat roots via hyphae that can survive in the soil in root debris of wheat plants. Ggt hyphae penetrate root cortical cells causing a root rot and progress into the base of the stem, disrupting water flow. Ggt is highly invasive on wheat roots, but has a wide host range, including wheat, triticale, barley and rye [2, 3]. Considerable effort has been exerted to understand the mechanisms underlying Ggt pathogenicity to help reduce Ggt-caused wheat losses [4,5,6,7,8]
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