Identification of effector candidate genes of Rhizoctonia solani AG-1 IA expressed during infection in Brachypodium distachyon

Abstract

Rhizoctonia solani is a necrotrophic phytopathogen belonging to basidiomycetes. It causes rice sheath blight which inflicts serious damage in rice production. The infection strategy of this pathogen remains unclear. We previously demonstrated that salicylic acid-induced immunity could block R. solani AG-1 IA infection in both rice and Brachypodium distachyon. R. solani may undergo biotrophic process using effector proteins to suppress host immunity before necrotrophic stage. To identify pathogen genes expressed at the early infection process, here we developed an inoculation method using B. distachyon which enables to sample an increased amount of semi-synchronous infection hyphae. Sixty-one R. solani secretory effector-like protein genes (RsSEPGs) were identified using in silico approach with the publicly available gene annotation of R. solani AG-1 IA genome and our RNA-sequencing results obtained from hyphae grown on agar medium. Expression of RsSEPGs was analyzed at 6, 10, 16, 24, and 32 h after inoculation by a quantitative reverse transcription-polymerase chain reaction and 52 genes could be detected at least on a single time point tested. Their expressions showed phase-specific patterns which were classified into 6 clusters. The 23 RsSEPGs in the cluster 1–3 and 29 RsSEPGs in the cluster 4–6 are expected to be involved in biotrophic and necrotrophic interactions, respectively.

Surveillance of Pathogenicity of Rhizoctonia solani Japanese Isolates with Varied Anastomosis Groups and Subgroups on Arabidopsis thaliana

“…These results suggested that the R. solani AG-1 IA would have a short biotrophic interaction at the early infection process on B. distachyon. This idea was also supported by the expression of the effector-like genes at the early infection stage up to 24 h prior to the formation of the necrotic lesions [36]. On the contrary, we also found that the exogenous application of BTH (acibenzolar-S-methyl) induced susceptibility of this pathogen in B. distachyon.…”

Brachypodium: 20 years as a grass biology model system; the way forward?

“…More recently, fungal small RNAs encoded by Fusarium graminearum were shown to suppress host defence gene expression [103] and a similar approach could also be a feature of the Magnaporthe grisea infections [104]. B. distachyon also lent itself to the development of an infection system with Rhizoctonia solani, based on which 61 secreted protein effectors were identified that could manipulate the host [105] via WRKY transcription factors BdWRKY38 and BdWRKY44 [106,107].…”

Comparative Field Evaluation and Transcriptome Analysis Reveals that Chromosome Doubling Enhances Sheath Blight Resistance in Rice

“…Rice sheath blight, caused by Rhizoctonia solani Kihn ( R. solani ), has a widespread impact on rice production worldwide (Li et al 2021 ; Molla et al 2020 ). It can reduce rice yields by up to 50% and dramatically affect rice quality, threatening global food security (Abdelsalam et al 2020 ; Singh et al 2019 ). The disease is difficult to control due to lack of resistant rice cultivars and favorable conditions for R. solani , such as warm temperatures and high humidity (Kouzai et al 2018 ).…”