, including cholesterol-lowering agents (monacolins), an antihypertensive substance (γ-aminobutyric acid) and an antioxidant (dimerumic acid) (Aniya et al., 2000; Lin et al., 2008; Pattanagul et al., 2008). However, the problem of safety emerged in 1995 when Blanc et al. (1995a) identified monascidin A, an antibacterial compound in RFR, as a nephrotoxic metabolite, citrinin. Thus, control of the production of citrinin is essential to increase the safety of Monascus-related products and extend their applications. In the past

decade, researchers have made considerable progress towards improving Monascus-related products using a process of optimization and traditional mutation breeding methods (Wang et al., 2004; Chen & Hu, 2005; Sayyad et al., 2007). Recently, some biosynthetic gene clusters involved in the biosynthesis of secondary metabolites of Monascus spp., such as citrinin AUY-922 cell line and

check details monacolin K, have been identified (Shimizu et al., 2007; Chen et al., 2008b). Based on the genetic information, a genetic modification method has also been proposed (Fu et al., 2007; Jia et al., 2010). Secondary metabolite production is controlled at an upper hierarchical level by many global mechanisms, in which many proteins encoded by genes not linked to the biosynthetic gene clusters are also involved in modulating fungal secondary metabolism, such as transcription factor, histone deacetylase, DNA methyltransferase, signalling proteins such as MAP kinases and cAMP-dependent protein kinase (Fox & Howlett, 2008). Heterotrimeric G-proteins, acting within G-protein signalling pathways to regulate multiple

physiological processes and that generally respond to environmental cues such as pH, temperature and nutrition, are also found to be involved in the regulation of secondary metabolite production in some toxigenic fungi (Hicks et al., 1997; Seo & Yu, 2006; Yu et al., 2008). Heterotrimeric G-proteins consist of three subunits: Gα, Gβ and Gγ. They function as ‘molecular switches’ in G-protein signalling Beta adrenergic receptor kinase pathways to regulate the duration and intensity of the signal, eventually going on to regulate downstream cell processes. Most characterized filamentous fungi possess three Gα proteins belonging to three distinct groups, Groups I, II and III, of which Group I is the most extensively studied (Li et al., 2007). Accumulating evidence has suggested that individual Group I Gα protein regulates multiple pathways. For example, dominant activating mutations in fadA in Aspergillus nidulans blocked both sterigmatocystin production and asexual sporulation, and the deletion of GzGPA1 in Gibberella zeae resulted in female sterility and enhanced deoxynivalenol and zearalenone production (Hicks et al., 1997; Yu et al., 2008).