Abstract
SummaryThe necrotrophic fungus Rhizoctonia cerealis is the major pathogen causing sharp eyespot disease in wheat (Triticum aestivum). Nucleotide‐binding leucine‐rich repeat (NB‐LRR) proteins often mediate plant disease resistance to biotrophic pathogens. Little is known about the role of NB‐LRR genes involved in wheat response to R. cerealis. In this study, a wheat NB‐LRR gene, named TaRCR1, was identified in response to R. cerealis infection using Artificial Neural Network analysis based on comparative transcriptomics and its defence role was characterized. The transcriptional level of TaRCR1 was enhanced after R. cerealis inoculation and associated with the resistance level of wheat. TaRCR1 was located on wheat chromosome 3BS and encoded an NB‐LRR protein that was consisting of a coiled‐coil domain, an NB‐ARC domain and 13 imperfect leucine‐rich repeats. TaRCR1 was localized in both the cytoplasm and the nucleus. Silencing of TaRCR1 impaired wheat resistance to R. cerealis, whereas TaRCR1 overexpression significantly increased the resistance in transgenic wheat. TaRCR1 regulated certain reactive oxygen species (ROS)‐scavenging and production, and defence‐related genes, and peroxidase activity. Furthermore, H2O2 pretreatment for 12‐h elevated expression levels of TaRCR1 and the above defence‐related genes, whereas treatment with a peroxidase inhibitor for 12 h reduced the resistance of TaRCR1‐overexpressing transgenic plants and expression levels of these defence‐related genes. Taken together, TaRCR1 positively contributes to defence response to R. cerealis through maintaining ROS homoeostasis and regulating the expression of defence‐related genes.
Highlights
Bread wheat (Triticum aestivum) is one of the most important staple crops
The results suggested that the transcriptional level of TaRCR1 was associated with wheat resistance degrees to R. cerealis
TaRCR1 transcription in CI12633 stems was enhanced by R. cerealis, and the induction reached a peak at 7 dpi with R. cerealis (Figure 1c)
Summary
The wheat sharp eyespot disease, primarily caused by a necrotrophic fungal pathogen Rhizoctonia cerealis, is one of the destructive diseases of wheat in some regions of the world. In terms of wheat acreage affected by sharp eyespot, China is the largest epidemic region in the world, as exemplified by the 8.1 million hectares of wheat infected in 2005 (Chen et al, 2013) and 9.33 million hectares in 2015 (http://www.agri.cn/V20/bc hqb/201501/t20150121_4344729.htm). Traditional resistance breeding is difficult as no wheat lines/cultivars with complete resistance to sharp eyespot have been identified, and the resistance in wheat accessions (CI12633, Luke and AQ2478883) is partial and controlled by multiple QTLs (quantitative trait loci, Cai et al, 2006; Chen et al, 2013). To improve wheat resistance to sharp eyespot, it is vital to identify genes that play important roles in the defence response and unravel their underlying functional mechanisms
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