Identification and characterization of a novel gene Aokap1 involved in growth and kojic acid synthesis in Aspergillus oryzae.

The elucidation of the mechanism for the growth and secondary metabolites in Aspergillus oryzae is important for industrial production and utilization. Here, we found that the expression of a novel gene Aokap1 was induced during the growth of A. oryzae. Sequence analysis revealed that AoKap1 has four transmembrane regions and is conserved in Aspergillus species. Disruption of Aokap1 caused the inhibition in mycelium growth and conidia formation, corresponding with reduced expression of brlA and abaA. Furthermore, deletion of Aokap1 resulted in elevated production of kojic acid, and the expression of kojA, kojR and kojT was up-regulated in Aokap1-disrupted strain. Meanwhile, overexpression of kojR resulted in the decreased expression of Aokap1, suggesting that disruption of Aokap1 increased kojic acid production by affecting the expression of kojA, kojR and kojT. The discovery of Aokap1 provides a new target for genetic modification of the growth and kojic acid production in A. oryzae.