Gene Function Of Histone Acetyltransferase In Aspergillus Niger

Aspergillus niger is an important industrial fermentation strain and the main strain for production of citric acid currently. Histone acetylation is one of the symbols of transcriptionally active of chromatin. Histone acetylation makes chromatin structure becoming loose from the tight and transcription factors more easily binding with the DNA sequences, which then causes the gene to be transcribed and the related proteins to be expressed. In addition, the acetylation process of lysine residue of histone is catalyzed by the histone acetyltransferase where the donor of the acetyl group is acetyl-CoA. Acetyl-CoA and oxaloacetate is catalyzed by citrate synthase to generated citric acid in A. niger. Therefore, this paper mainly studied the impact of histone acetylation on the growth and fermentation of citric acid in A. niger by deleting relative genes coding histone acetyltransferases.In this paper, A. niger wild type ATCC1015 was used, the main results were as follow:1. We chose pFGL59Ble that reconstructed by our researching group as the vector for knocking out the genes GNAT, MOZ/SAS and HATb of HATs in A. niger. The recombinant plasmids were electroporated into Agrobacterium tumefaciens, respectively. By A. tumefaciens-mediated transformation of A. niger, the exogenous gene carrying the homologous fragments was transferred into A. niger, then homologous recombination occurred. The histone acetyltransferase single gene knockout strains AGNAT, AMOZ/SAS and AHATb were successfully obtained by screening the transformants.2. The phenotypic analysis by microscope technology showed that the gene deletion strains AGNAT and AHATb had no significant differences in respect of growth rate and phenotype with the wild type. But the amount of spores in these two mutants was slightly lower than the wild-type strain. The mutant AMOZ/SAS growed normally, but spores producing more slowly and had less spores than the wild type, that the quantity of spores was reduced by about 60%.3. After flask fermentation experiments of three mutants and the wild strain, HPLC was used for analysis of citric acid. The results showed that the yield of citric acid by the mutant AHATb and the wild type was basically consistent, about 79 g/L. Compared to the wild type, citrate production of AGNAT and AMOZ/SAS was lower, were approximately 72.38 g/L,65.24 g/L, respectively. The yield of citric acid was reduced by 14.6% in AMOZ/SAS.The results showed that MOZ/SAS had more significant in regulating the spores producing and citric acid production in A. niger.