A Subunit of the COP9 Signalosome, MoCsn6, Is Involved in Fungal Development, Pathogenicity, and Autophagy in Rice Blast Fungus

The COP9 signalosome (CSN) is a highly conserved protein complex in eukaryotes, affecting various development and signaling processes. To date, the biological functions of the COP9 signalosome and its subunits have not been determined in Magnaporthe oryzae. In this study, we characterized the CSN in M. oryzae (which we named MoCsn6) and analyzed its biological functions. MoCsn6 is involved in fungal development, autophagy, and plant pathogenicity. Compared with the wild-type strain 70-15, DMocsn6 mutants showed a significantly reduced growth rate, sporulation rate, and germ tube germination rate. Pathogenicity assays showed that the Delta Mocsn6 mutants did not cause or significantly reduced the number of disease spots on isolated barley leaves. After the MoCSN6 gene was complemented into the Delta Mocsn6 mutant, vegetative growth, sporulation, and pathogenicity were restored. The Osm1 and Pmk1 phosphorylation pathways were also disrupted in the DMocsn6 mutants. Furthermore, we found that MoCsn6 participates in the autophagy pathway by interacting with the autophagy core protein MoAtg6 and regulating its ubiquitination level. Deletion of MoCSN6 resulted in rapid lipidation of MoAtg8 and degradation of the autophagic marker protein green fluorescent protein-tagged MoAtg8 under nutrient and starvation conditions, suggesting that MoCsn6 negatively regulates autophagic activity. Taken together, our results demonstrate that MoCsn6 plays a crucial role in regulating fungal development, pathogenicity, and autophagy in M. oryzae.

Automated summary

The COP9 signalosome (CSN) plays an important role in regulating fungal development, pathogenicity, and autophagy in Magnaporthe oryzae. The CSN subunit MoCsn6 is involved in vegetative growth, sporulation, and plant infection. Deletion of MoCSN6 disrupts the Osm1 and Pmk1 phosphorylation pathways and negatively regulates autophagic activity by interacting with MoAtg6 and controlling its ubiquitination level.