A septation related gene AcsepH in Acremonium chrysogenum is involved in the cellular differentiation and cephalosporin production.

T-DNA inserted mutants of Acremonium chrysogenum were constructed by Agrobacterium tumefaciens-mediated transformation (ATMT). One mutant 1223 which grew slowly was selected. TAIL-PCR and sequence analysis indicated that a putative septation protein encoding gene AcsepH was partially deleted in this mutant. AcsepH contains nine introns, and its deduced protein AcSEPH has a conserved serine/threonine protein kinase catalytic (S_TKc) domain at its N-terminal region. AcSEPH shows high similarity with septation H proteins from other filamentous fungi based on the phylogenetic analysis of S_TKc domains. In sporulation (LPE) medium, the conidia of AcsepH mutant was only about one-seventh of the wild-type, and more than 20% of conidia produced by the mutant contain multiple nuclei which were rare in the wild-type. During fermentation, the AcsepH disruption mutant grew slowly and its cephalosporin production was only about one quarter of the wild-type, and the transcription analysis showed that pcbC expression was delayed and the expressions of cefEF, cefD1 and cefD2 were significantly decreased. The vegetative hyphae of AcsepH mutant swelled abnormally and hardly formed the typical yeast-like cells. The amount of yeast-like cells was about one-tenth of the wild-type after fermentation for 5days. Comparison of hyphal viabilities revealed that the cells of AcsepH mutant died easily than the wild-type at the late stage of fermentation. Fluorescent stains revealed that the absence of AcsepH in A. chrysogenum led to reduction of septation and formation of multinucleate cells. These data indicates that AcsepH is required for the normal cellular septation and differentiation of A. chrysogenum, and its absence may change the cellular physiological status and causes the decline in cephalosporin production.