The Aspergillus fumigatus β-1,3-glucanosyltransferase Gel7 plays a compensatory role in maintaining cell wall integrity under stress conditions

Aspergillus fumigatus is an opportunistic fungal pathogen that causes fatal invasive aspergillosis among immunocompromised patients. The cell wall beta-1,3-glucan is mainly elongated by beta-1,3-glucanosyltransferase Gel family, which is vital for growth and virulence of A. fumigatus. Although seven members of Gels have been annotated, only Gel1, Gel2 and Gel4 were characterized. In this study, the function of Gel7 was analyzed for the first time, by constructing delta gel7, delta gel7 delta cwh41 and delta gel1 delta gel7 delta cwh41 separately. Disruption of gel7 alone did not result in any obvious phenotype except an abnormality in conidia formation, whereas delta gel7 delta cwh41 and delta gel1 delta gel7 delta cwh41 exhibited abnormal conidiogenesis, a heat-induced delay of germination and a severe decrease in beta-1,3-glucan content. Our results suggested that the A. fumigatus beta-1,3-glucanosyltransferase Gel7 was involved in conidiation and was compensated for the cell wall beta-1,3-glucan defects when Gel1 and Gel2 lost their functions, especially at an elevated temperature.