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A glycine-rich poly(U)-binding nuclear protein regulates asexual development and virulence of Magnaporthe oryzae

Jun Yang: China Agricultural University

<div>Glycine-rich RNA-binding proteins (GRPs) are involved in diverse biological processes and play important roles through binding RNAs and proteins. We here identified a novel gene MoGRP1 encoding a GRP from Magnaporthe oryzae, which was important to fungal virulence and development. The ΔMogrp1 mutants exhibited severe defects in growth, conidiation, appressorium formation, invasive hyphal development, and virulence. The ΔMogrp1 mutants were also deficient in cell wall integrity and responses to different stresses. MoGrp1 was localized in nuclei and co-immunoprecipitated with several components of the spliceosome, including subunits of U1 snRNP and U2 snRNP. Moreover, MoGrp1 possessed a high binding capacity to poly(U). MoGrp1 has no homologs in yeasts, plants, and animals, suggesting it might function as a unique auxiliary splicing factor. MoGrp1 has an N-terminal RNA recognition motif (RRM) domain and a C-terminal glycine-rich domain with four Arg-Gly-Gly (RGG) repeats. Domain deletion assays showed that both the RRM domain and RGG repeats were essential to fully function of MoGrp1. The full sequence of nine amino acids between the first and the second RGG repeats was essential to nuclear localization and biological functions of MoGrp1. In summary, our results indicate that MoGrp1 is a novel component of the spliceosome unique to filamentous fungi and regulates fungal virulence, development, and responses to stresses in the rice blast fungus.</div>