Toward identification of genetic components of fungal immunity using the rice blast fungus, Magnaprothe oryzae as a model
Date
2016
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Publisher
University of Delaware
Abstract
Magnaporthe oryzae is the most devastating fungal pathogen of rice, and the causal agent of rice blast disease. It is an ascomycete hemibiotrophic fungus that infects leaves, stems, panicles and roots, killing enough rice to feed 60 million people annually. To control the disease is not easy as many R genes are overcome within several years. In the experiments presented here, we aim to better understand how the fungus defends itself against potential bacterial biocontrol agents, by identifying components of the fungal immune system. Lysobacter enzymogenes wild type strain C3, Pseudomonas chloroaphis strain EA105 and S-4, a strain that is similar to Bacillus amyloliquefaciens strain HY7 with 99% identity are being studied as potential biological control agents against M. oryzae. We sought to identify the modes of action that are initiated in the fungus once a bacterial-fungal interaction is detected, in regards to defense against the bacteria. The methods used to accomplish our goal were to (a) use of bioinformatics to look for conserved genes across many fungi from a suite of 12 potential fungal immune genes, (b) diffusible plate assays to determine the nature of the biocontrol against M. oryzae, and (c) real-time qRT-PCR to identify fungal genes that expressed during bacterial interaction. From our experiments we found that all three bacteria were able to inhibit the growth of M. oryzae in approximately 4 days post-inoculation. Of the 5 fungal genes tested for expression during bacterial interaction only two genes, one a CFEM domain containing protein and the other a NACHT domain-containing protein were found to have significant differences when expressed among the different bacteria. Both domains are known to be involved in protein-protein interactions and could potentially detect secreted bacterial molecules. These results help provide insight on exactly how M. oryzae may be defending itself and in proving that these bacteria are indeed good candidates as biological control agents against M. oryzae.