ROLE OF ALTERNATIVE RAD21 PARALOGS OF COHESIN COMPLEX 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. In yeast the cohesin subunit rad21 has two paralogs; one functions in mitosis and the other in 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 Fusarium 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 and rec8 germinate less effectively than WT under cell cycle perturbations. rad21nc mutants show an increase in chlamydospore numbers in comparison with WT. Finally, both rad21nc and rec8 mutants show reduced invasive growth in tomato fruits. The possible role of alternative cohesin complexes in fungal pathogenesis is under investigation.