<i>Coprinopsis cinerea</i> Cla4 protein kinase is required for the assembly of the hyphal tip apparatus that enables the rapid linear growth of apical cells

The <i>C. cinerea</i> septins are observed at the hyphal tip and septum in the growing vegetative hyphae. In <i>Saccharomyces cerevisiae</i>, septin dynamics have been suggested to be regulated by septin phosphorylation through protein kinases such as Cla4. To gain insight into the relationship between <i>C. cinerea</i> septins and <i>C. cinerea</i> Cla4 protein kinase (Cc.Cla4), we conducted disruption of the <i>C. cinerea cla4</i> gene (<i>Cc.cla4</i>) by CRISPR/Cas9 system and analyzed the phenotypes of <i>Cc.cla4</i>Δ strains. The vegetative hyphae of the <i>Cc.cla4</i>Δ strains grow slowly in the zigzag shape and are highly branched compared to the wild-type hyphae. The enhanced green fluorescent protein (EGFP) tagged Cc.Cdc3 septin in the <i>Cc.cla4</i>Δ strain was observed in the growing vegetative hyphae. Although EGFP-Cc.Cdc3 signals localized at the plasma membrane of the hyphal tip region, they did not accumulate as a dome with a hole at the hyphal tip as observed in the wild type. Instead, the Cc.Cdc3 was found to stay at the hyphal tip, which split into two tips thereafter. These results suggest that Cc.Cla4 is required for assembly of the hyphal tip apparatus that enables the rapid linear growth of the apical cells.