The outer kinetochore DASH complex (also known as the Dam1 complex) ensures proper spindle structure and chromosome segregation. While DASH complex protein requirement diverges among different yeasts, its role in filamentous fungi has not yet been investigated. We studied the dynamics and role of middle (Mis12) and outer (Dam1 and Ask1) kinetochore proteins in the filamentous fungal pathogen, Magnaporthe oryzae, which undergoes multiple cell cyclelinked developmental transitions. While Mis12 was constitutively present in the nucleus, Dam1 and Ask1 were recruited only during mitosis. Although Dam1 was not required for viability, loss of its function (dam1Δ) delayed mitotic progression, resulting in impaired conidial and hyphal development. Both Dam1 and Ask1 also localised to the hyphal tips, in the form of punctae oscillating back and forth from the growing ends, suggesting that Magnaporthe DASH complex proteins may play a non-canonical role in polarised growth during interphase, in addition to their function in nuclear segregation during mitosis. Impaired appressorial (infection structure) development and host penetration in the dam1Δ mutant suggest that fungus-specific Dam1 complex proteins could be an attractive target for a novel anti-fungal strategy. This article has an associated First Person interview with the first author of the paper.

The outer kinetochore DASH/DAM complex ensures proper spindle structure and chromosome segregation. While DASH complex protein requirement diverges among different yeasts, its role in filamentous fungi has not been investigated so far. We studied the dynamics and role of middle (Mis12) and outer (Dam1 and Ask1) kinetochore proteins in the filamentous fungal pathogen, Magnaporthe oryzae, which undergoes multiple cell cycle linked developmental transitions. Both Dam1 and Ask1, unlike Mis12, were recruited to the nucleus specifically during mitosis. While Dam1 was not required for viability, loss of its function (dam1Δ mutant) delayed mitotic progression, resulting in impaired conidial and hyphal development in Magnaporthe. Intriguingly, both Dam1 and Ask1 also localised to the hyphal tips, in the form of punctae oscillating back and forth from the growing ends, suggesting that Magnaporthe DASH complex proteins may play a non-canonical role in polarised growth during interphase, in addition to their function in nuclear segregation during mitosis. Impaired appressorial (infection structure) development and function in the dam1Δ mutant suggest that fungus-specific Dam1 complex proteins could be an attractive target for a novel anti-fungal strategy.Summary StatementDASH complex proteins are differentially recruited to the nucleus during cell division and are intriguingly involved in polarised growth during development and differentiation in the rice blast fungus.