Submitted to: Rice Technical Working Group Meeting Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 1/15/2008
Publication Date: 3/1/2008
Citation: Jia, Y., Wang, G., Valent, B. 2008. Global gene expression of rice after infections with rice blast and sheath blight pathogens. In: Proceedings of the 32nd Rice Technical Working Group Meetings, February 18-21, 2008, San Diego, CA. 2008. CDROM. Interpretive Summary:
Technical Abstract: Rice (Oryza sativa) production worldwide has been challenged by increased new virulent pathogens. Over the years, genetic diversity needed for fighting diseases has been decreasing in cultivated rice around the globe. This presents a real challenge for rice crop protection. In an effort to develop effective methods to control rice diseases, phenotypical, molecular and biochemical analysis of rice plants after infection with rice blast (Magnaporthe oryzae) and sheath blight (Rhizoctonia solani) fungi were examined by global gene expression using DNA microarray and Serial Analysis of Gene Expression (SAGE). It was observed that the infection of rice by M. oryzae is a biotrophic process where nutrients from live cells are taken up by the pathogen at the early stage of infection within 24 hrs. In contrast, the infection of rice by R. solani is a necrotrophic process where the pathogen produces enzymes and toxins to kill the cells for its infection. Using total RNA prepared from leaves at 3 to 4 leaf stage at 6, 16, 24 hr after inoculation, gene expression profiles were analyzed and compared. Most of defense responsive genes are reduced to a normal level three days earlier in the interactions of O. sativa /R. solani than in the interactions of O. sativa/M. oryzae. Most of the differentially expressed genes identified by DNA microarray were confirmed by SAGE except that the fold induction varied significantly between the two platforms. To date, uniquely expressed genes specific to interaction of O. sativa /M. oryzae, and to O. sativa /R. solani were identified and confirmed using real time PCR. Additional critical genes were also identified in a suppression subtractive hybridization cDNA library after the sheath blight pathogen infection and verified by real time PCR using RNA prepared after blast infection. Overall, our results suggest that several common signaling pathways were activated at different time points after pathogen infection. These molecular responses concur with differential phenotypical reactions observed under light microscopes. The cause and effect of expressions of these differentially and highly expressed genes in relation to the invasive growth of the pathogen, and to the defense responses of rice is being analyzed and the implication for crop protection will be presented.