| Abstrakt: |
aflJresides within the aflatoxin biosynthetic gene cluster adjacent to the pathway regulatory gene aflRand is involved in aflatoxin production, but its function is unknown. Over-expression of aflJin the aflatoxin-producing strain 86-10 resulted in increased aflatoxin. In an effort to study the function and regulation of aflJ, strain 649-1 lacking the entire biosynthetic cluster was transformed with either reporter constructs, expression constructs, or cosmid clones and analysed for gene expression or metabolite accumulation. Over-expression of aflJdid not result in elevated transcription of ver-1, omtAor aflR. To determine if over-expression of aflJleads to an increase in early pathway intermediates, strain 649-1 was transformed with cosmid 5E6 and either gpdA::aflJalone, gpdA::aflRalone, or aflJand aflRtogether. Cosmid 5E6 contains the genes pksA, nor-1, fas-1, and fas-2, which are required for the biosynthesis of the early pathway intermediate averantin. 649-1 transformants containing 5E6 alone produced no detectable averantin. In contrast, 5E6 transformants with gpdA::aflRproduced averantin, but only half as much as those transformants containing both aflRand aflJ. Northern blot analysis showed that 5E6 transformants containing both aflRand aflJhad five times more pksAtranscripts and four times more nor-1transcripts than 5E6 transformants containing gpdA::aflRalone. Further, aflJtranscription was regulated by aflR. Over-expression of aflRresulted in elevated aflJtranscription. aflJappears to modulate the regulation of early genes in aflatoxin biosynthesis. |
