Analysis of putative sclerotia maturation-related gene expression in Rhizoctonia solani AG1-IA

Abstract

Rhizoctonia solani AG1-IA (R. solani AG1-IA) is a major soil-borne fungal pathogen of maize that causes significant yield losses in all maize-growing regions worldwide. The sclerotium produced by R. solani AG1-IA can overwinter in grass roots or diseased plants and infect crops the following year. The molecular mechanism underlying sclerotium formation in R. solani is poorly understood. In this study, we constructed the cDNA library of the R. solani AG1-IA pathogenic strain WF-9, from which 329 high-quality expressed sequence tags (ESTs) were obtained. Of the 250 clustered unigenes, 12 genes were selected for further expression analysis during the three stages of sclerotial growth (mycelium, initiation of sclerotium, and maturation of sclerotium). The results of expression analysis support the previously suggested roles of chitin synthase D and exo-beta-1,3-glucanase in facilitating sclerotial growth through preservation of water content and energy. In addition, cytochrome P450, NADPH oxidase, catalase (CAT), acyl-CoA oxidase 1 (ACOX1), mitogen-activated protein kinase (MAPK), mitogen-activated protein kinase HOG1 (HOG 1), and the G-protein α subunit play important roles in balancing reactive oxygen species (ROS) levels during sclerotial development. The findings of this study can help understand the molecular mechanism of sclerotial development further.

Heritability and gene functions associated with sclerotia formation of Rhizoctonia solani AG-7 using whole genome sequencing and genome-wide association study

“…Specifically for R. solani , previous studies showed fewer sclerotia were produced when cultured on the hydroxyl radial scavenger-amended or ascorbic acid-amended media [25, 26]. Consistently, exogenous application of H 2 O 2 resulted in more sclerotia formation [27–29], and the application of the catalase inhibitor aminotriazole resulted in increased sclerotia formation [27]. In addition, a sclerotia-forming R. solani isolate accumulated and secreted more H 2 O 2 than a non-sclerotia-forming isolate, suggesting that H 2 O 2 may be the key ROS for initiating sclerotia formation [23].…”

“…Sclerotia are not only the survival structures to overcome environmental stresses, but also the primary and/or secondary inocula to initiate a disease cycle for many plant-pathogenic fungi. In particular for R. solani, the amount of sclerotia has been reported to be positively corelated with disease incidence in rice fields [104,105], and several studies have applied proteomic, metabolomic and transcriptomic approaches to understand sclerotia development of R. solani [28][29][30][31][32][33]106]. However, field isolates could produce sclerotia with various numbers and sizes, and whether or not the sclerotia-forming capability is influenced by genetic effects remains unclear.…”

“…For sclerotia number, many ROS-response genes such as thioredoxin and thioredoxin reductase were found in the LD region associated with sclerotia number. Previous studies have demonstrated that accumulation of ROS is required for sclerotia differentiation [22,23,28,29]. However, the side effect of ROS toxicity requires other detoxifying mechanisms to protect fungal cells.…”