Paper accepted: “Comprehensive phenotypic analysis of multiple gene deletions of α-glucan synthase and Crh-transglycosylase gene families in Aspergillus niger highlighting the versatility of the fungal cell wall”

Today, the first paper originating from Katharina Ost’s doctoral project on engineering the fungus Aspergillus niger for optimized protein production has been accepted for publication in the renowned journal The Cell Surface. For this collaborative project, Kathy worked in three labs, most importantly in the Osnabrück group of Prof. Mareike Dirks-Hofmeister, but also in Prof. Arthur Ram’s lab in Leiden where she collaborated with Mark Arentshorst, and, a little also, in our group in Münster. Kathy knocked out the five alpha-glucan synthase genes of the fungus one by one, to probe their influence on cell wall integrity. Surprisingly, even though alpha-glucans were recently identified as integral components of both the rigid core and the more flexible matrix of fungal cell walls, removing these polymers did not seem to have a strong impact. In a previous collaboration, we had already knocked out all the seven crh genes of the fungus which code for enzymes thought to be responsible for the covalent cross-links between chitin and beta-glucans in the rigid core of the wall. There also, the effect had been surprisingly small. Now, Kathy combined the two approaches, generating a twelve-fold knock out. And still, little effect! Only under stress, a limited impact was seen in some of the knock-out strains. It shows the surprising flexibility of fungal cell walls which appear to follow a less rigid architectural plan than the plant cell wall with its fibers-in-a-matrix concept. Kathy and Mareike hope that this flexibility will allow them to modify the cell wall in such a way that it presents less of a barrier to protein export.