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Magnaporthe oryzae Auxiliary Activity Protein MoAa91 Functions as Chitin-Binding Protein to Induce Appressorium Formation on Artificial Inductive Surfaces and Suppress Plant Immunity

Summary

This research reveals how a rice blast fungus protein called MoAa91 helps the fungus infect rice plants in two ways: by helping form infection structures and by blocking plant immune responses. This discovery advances our understanding of plant diseases and could lead to better crop protection strategies. Impacts on everyday life: – Helps explain why some fungal diseases are so destructive to food crops – Could lead to development of better fungicides and disease-resistant crops – May reduce crop losses and improve food security – Provides insights for developing more sustainable agriculture practices – Could reduce the economic impact of plant diseases on farmers

Background

The rice blast fungus Magnaporthe oryzae generates infection structures called appressoria in response to surface cues, which is regulated by various signaling molecules including G-proteins, regulators of G-protein signaling (RGS), MAP kinase pathways, cAMP signaling, and TOR signaling pathways. M. oryzae encodes eight RGS and RGS-like proteins, with MoRgs1, MoRgs3, MoRgs4, and MoRgs7 being particularly important in appressorium development.

Objective

To explore the mechanisms by which RGS proteins regulate appressorium development in M. oryzae through comparative transcriptomic analysis, and to characterize the function of the identified auxiliary activity family 9 protein MoAa91 in appressorium formation and plant infection.

Results

The study identified MoAa91 as a secreted protein regulated by the transcription factor MoMsn2. MoAa91 was found to function as an inducer of appressorium formation on artificial surfaces and compete with the rice immune receptor CEBiP for chitin binding. The ΔMoaa91 mutant showed delayed appressorium formation on artificial surfaces and reduced virulence. MoAa91 was demonstrated to suppress host immunity by competing with CEBiP for chitin binding, thereby preventing chitin-triggered immune responses.

Conclusion

MoAa91 serves as both a signaling molecule for appressorium development and an effector that suppresses host immunity. This reveals a novel mechanism by which RGS and RGS-like proteins regulate pathogen-host interactions in M. oryzae through the dual function of MoAa91 in appressorium formation and immune suppression.
  • Published in:mBio,
  • Study Type:Basic Research,
  • Source: 10.1128/mBio.03304-19
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