Identification and Characterization of In-planta Expressed Secreted Effector Proteins from Magnaporthe oryzae

Rice blast disease, caused by the fungus Magnaporthe oryzae, is one of the most serious diseases of rice. Interactions between rice and M. oryzae involve the recognition of cellular components and the exchange of complex molecular signals from both partners. How these interactions occur in rice is still elusive. Previously, we employed gene expression profiling, including robust-long serial analysis of gene expression (RL-SAGE), massively parallel signature sequencing (MPSS), and sequencing by synthesis (SBS), to examine transcriptome profiles of infected rice leaves. A total of 6,413 in-planta expressed fungal genes, including 851 genes encoding putative effector proteins, were identified. To elucidate the molecular basis of interactions between rice and M. oryzae upon infection, we combined the results from gene expression profiling with high throughput gene cloning, and rapid protoplast transient expression assay for large-scale identification of M. oryzae effector proteins that induce cell death in rice plants. In total, seven M. oryzae proteins were found to induce cell death in rice protoplasts and six of them were found to induce cell death in the non-host plant, Nicotiana benthamiana. However, this cell death only occurred when the proteins contained the signal peptide for secretion to the extracellular space. Although these seven M. oryzae effectors are diverse in their sequence and structure, the physiological basis of cell death induced by most of these effectors is similar. Among all identified effectors, three effectors, i.e., MGG_05232, MGG_08370, MGG_08409, contain carbohydrate-binding modules (CBMs). To elucidate the pathogenesis function of the three CBM-containing effectors, we generated transgenic M. oryzae strains that carried out gene replacement and gene overexpression. Among the three of them, the MGG_08409 effector containing cellulose binding domain showed pathogenic function in rice. In addition, MGG_08409 binds to cellulose, the component of plant cell wall, and has glucanase activity against cellulose substrate. This study demonstrates that our integrative genomic approach is effective for the identification of in-planta expressed cell death-inducing effector from M. oryzae, which may play important role facilitating colonization and fungal growth during infection. Characterization of these fungal effector proteins will provide new insights into the molecular basis of the rice and M. oryzae interactions.

Name thesis:degree_name

Doctor of Philosophy

Level thesis:degree_level

doctoral

Discipline thesis:degree_discipline

Plant Pathology

Grantor dc:publisher

The Ohio State University

Year dc:date

2013

Author dc:creator

• Songkumarn, Pattavipha

Contributors dc:contributor

• Wang, Guo-Liang

• Plant Pathology
• Magnaporthe oryzae
• effectors
• CBMs

Statement dc:rights

• unrestricted
• This thesis or dissertation is protected by copyright: all rights reserved. It may not be copied or redistributed beyond the terms of applicable copyright laws.

Language dc:language

English

Repository record dc:identifier

http://rave.ohiolink.edu/etdc/view?acc_num=osu1357158502

OAI identifier oai:identifier

oai:etd.ohiolink.edu:osu1357158502