Identification of defense-related genes in rice responding to challenge by Rhizoctonia solani

Theor Appl Genet (2008) 116:501516 DOI 10.1007/s00122-007-0686-y

ORIGINAL PAPER

IdentiWcation of defense-related genes in rice responding to challenge by Rhizoctonia solani

Chang-Jiang Zhao Ai-Rong Wang Yu-Jun Shi Liu-Qing Wang Wen-De Liu Zong-Hua Wang Guo-Dong Lu

Received: 11 January 2007 / Accepted: 23 November 2007 / Published online: 13 December 2007 Springer-Verlag 2007

Abstract Rice sheath blight, caused by Rhizoctonia solani is one of the major diseases of rice. The pathogen infects rice plants directly through stomata or using lobate appressoria and hyphal masses called infection cushions. The infection structures were normally found at 36 h post-inoculation. During infection, the pathogenesis-related genes, PR1b and PBZ1 were induced in rice plants. To identify rice genes induced early in the defense response, suppression subtractive hybridization (SSH) was used to generate a cDNA library enriched for transcripts diVerentially expressed during infection by R. solani. After diVer-ential screening by membrane-based hybridization and subsequent conWrmation by reverse Northern blot analysis, selected clones were sequenced. Fifty unique cDNA clones were found and assigned to Wve diVerent functional categories. Most of the genes were not previously identiWed as being induced in response to pathogens. We examined expression of 100 rice genes induced by infection with Magnaporthe grisea, Xanthomonas oryzae pv. oryze (Xoo) and X. oryzae pv. oryzicola (Xooc). Twenty-Wve of them were found to be diVerentially expressed after the sheath

blight infection, suggesting overlap of defense responses to diVerent fungal and bacterial pathogens infection.

Introduction

Rice sheath blight, caused by the fungal pathogen Rhizoctonia solani Kuhn [Sexual stage: Thanetophorus cucumeris (Frank) Donk] is one of the major production constraints in rice-growing countries of the world. Currently, the best method for controlling sheath blight is applying commercial fungicides. Breeding for sheath blight resistant rice plants has not been very successful mainly because of lack of resistant donors in the cultivated varieties of rice (Bon-mann et al. 1992).

The most common resistance reaction in plants is the hypersensitive response (HR), which localizes the pathogen at the infection site through cell death. The local responses at the point of infection also trigger a subsequent non-speciWc resistance that occurs throughout the entire plant; this phenomenon is called systemic acquired resistance (SAR). Typical SAR results in an increase of endogenous salicylic acid (SA) and transcriptional activation of defense-related...