Deletion of GEL2 encoding for a beta(1-3)glucanosyltransferase affects morphogenesis and virulence in Aspergillus fumigatus

The first fungal glycosylphosphatidylinositol anchored beta(1 - 3) glucanosyltranferase (Gel1p) has been described in Aspergillus fumigatus and its encoding gene GEL1 identified. Glycosylphosphatidylinositolanchored glucanosyltransferases play an active role in the biosynthesis of the fungal cell wall. We characterize here GEL2, a homologue of GEL1. Both homologues share common characteristics: (i) GEL1 and GEL2 are constitutively expressed during over a range of growth conditions; (ii) Gel2p is also a putative GPI- anchored protein and shares the same b ( 1 3) glucanosyltransferase activity as Gel1p and (iii) GEL2, like GEL1, is able to complement the Delta gas1 deletion in Saccharomyces cerevisiae confirming that Gelp and Gasp have the same enzymatic activity. However, disruption of GEL1 did not result in a phenotype whereas a Delta gel2 mutant and the double mutant Delta gel1 Delta gel2 exhibit slower growth, abnormal conidiogenesis, and an altered cell wall composition. In addition, the Delta gel2 and the Delta gel1 Delta gel2 mutant have reduced virulence in a murine model of invasive aspergillosis. These data suggest for the first time that beta(1-3) glucanosyltransferase activity is required for both morphogenesis and virulence in A. fumigatus.