A fungal specific cohesin subunit regulates developmental biology in Fusarium oxysporum
Cohesin is an essential protein complex that assures sister chromatid cohesion and participates in DNA repair, transcription and maintenance of chromosome structure. The cohesin subunit rad21 has several paralogs; each paralog dictates the role of cohesin in different developmental stages such as mitosis and meiosis. We identified three rad21 paralogs in the fungal pathogen Fusarium oxysporum. One paralog is probably the canonical essential rad21 protein. Another is the meiosis specific gene rec8. The third one is non-conserved rad21 paralog (rad21nc) that was identified only in a small subset of fungi and could be horizontally transferred to F. oxysporum from Fusarium solani. All rad21 paralogs are expressed in F. oxysporum although the canonical paralog is expressed much more than the others. F. oxysporum strains deleted for the rad21nc paralog exhibit irregular conidiation, delayed maturation of hyphae, and defects in spore germination under mitosis stress. These phenotypes are leading us to hypothesize that rad21nc paralog functions in a checkpoint-like response during fungal development. The possible role of such checkpoint protein in fungal pathogenesis and will be further discussed.