Gibberella zeae의 이차대사산물 생성에 관여하는 유전자들의 기능 분석

Abstract

Head blight fungus Gibberella zeae (anamorph Fusarium graminearum) produces various kinds of secondary metabolites such as zearalenone (ZEA) and triacylglycerides. ZEA which is accumulated in contaminated grains causes estrogenic disorders in animals and humans. Triacylglycerides is required for perithecium development and accumulated for sexual development in G. zeae. In first, I focused on identifying genes responsible for ZEA metabolism. Through microarray analysis between ZEA responsive genes and zeb2 dependent genes, total 674 genes were identified to be down- or up-regulated 3-fold or more in either condition than in the reference. To find transporters of ZEA, three zeb2 responsive ABC transporters were selected from microarray for functional study. Based on targeted knock-out, northern analysis and ZEA production analysis, it was identified that deletion of ZRA1 resulted in reduced ZEA production and overexpression of it increased ZEA production compared to wild-type strain. ZRA1 localized to the plasma membrane and vacuoles indicating possible roles of ZRA1 in ZEA production rather than export of ZEA. This study indicated that ZRA1 is involved in ZEA production and shares a common regulatory mode with ZEA cluster genes by ZEB2 or ZEA. In second, I identified a major triacylglyceride as 1-Palmitoyl-2-oleoyl-3-linoleoyl-rac-glycerol (POL) which is crucial for perithecium development in G. zeae. Functions of two acetyl-CoA synthetases (ACS1 and ACS2) were studied to identify production mechanisms of acetyl-CoA which is an essential building block for the biosynthesis of triglycerides. Deletion of ACS1 resulted in a defect in sexual development that was mainly due to a reduction in POL production. ACS2 has accessorial functions for ACS1 and has compensatory functions for ATP citrate lyase as a nuclear acetyl-CoA producer. ACS1 is required for acetate utilization and lipid biosynthesis, and ACS2 has some overlapping functions with both ACS1 and ACL. Both studies revealed several important genes in metabolite productions crucial for physiological processes and mycotoxin production in G. zeae.