Abstract
Rhizoctonia solani AG1 IA is a soil-borne fungal phytopathogen that can significantly harm crops resulting in economic loss. This species overwinters in grass roots and diseased plants, and produces sclerotia that infect future crops. R. solani AG1 IA does not produce spores; therefore, understanding the molecular mechanism of sclerotia formation is important for crop disease control. To identify the genes involved in this process for the development of disease control targets, the transcriptomes of this species were determined at three important developmental stages (mycelium, sclerotial initiation, and sclerotial maturation) using an RNA-sequencing approach. A total of 5,016, 6,433, and 5,004 differentially expressed genes (DEGs) were identified in the sclerotial initiation vs. mycelial, sclerotial maturation vs. mycelial, and sclerotial maturation vs. sclerotial initiation stages, respectively. Moreover, gene ontology (GO) and kyoto encyclopedia of genes and genomes (KEGG) analyses showed that these DEGs were enriched in diverse categories, including oxidoreductase activity, carbohydrate metabolic process, and oxidation-reduction processes. A total of 12 DEGs were further verified using reverse transcription quantitative PCR. Among the genes examined, NADPH oxidase 1 (NOX1) and superoxide dismutase (SOD) were highly induced in the stages of sclerotial initiation and maturation. In addition, the highest reactive oxygen species (ROS) production levels were detected during sclerotial initiation, and enzyme activities of NOX1, SOD, and catalase (CAT) matched with the gene expression profiles. To further evaluate the role of ROS in sclerotial formation, R. solani AG1 IA was treated with the CAT inhibitor aminotriazole and H2O2, resulting in the early differentiation of sclerotia. Taken together, this study provides useful information toward understanding the molecular basis of R. solani AG1 IA sclerotial formation and maturation, and identified the important role of ROS in these processes.
Highlights
Rhizoctonia solani is a soil-borne pathogen belonging to the class Agaricomycetes, family Ceratobasidiaceae, that causes various plant diseases and attacks crops
Transcriptome sequencing reads quality inspection and sample correlation analysis during sclerotia formation of R. solani AG1 IA Total RNAs were isolated from RWF9M, RWF9SI, and RWF9S (Fig. 1)
These results showed that the data quality of the transcriptome was high and suitable for transcriptome analysis
Summary
Rhizoctonia solani is a soil-borne pathogen belonging to the class Agaricomycetes, family Ceratobasidiaceae, that causes various plant diseases and attacks crops (maize, potatoes, rice, and soybean). Maize sheath blight is one of the most serious and widely distributed diseases caused by R. solani AG1 IA, resulting in severe yield losses in maize-cultivating areas worldwide. The sclerotium is a special structure of R. solani that overwinters in the soil or diseased plants, and can survive under adverse conditions (e.g., low temperature) for long periods (Rush & Lee, 1983; Boland et al, 2004). Sheath blight disease-resistant varieties of maize are available, these varieties are limited; treating maize with fungicides remains the main approach to control the spread of R. solani in crops (Zhao et al, 2006). Since R. solani AG1 IA does not produce spores, the growth and germination of sclerotial are the key to maintaining the life of R. solani
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