Abstract
Strains of Monascus filamentous fungal species have been used to produce fermented foods in Asian countries, such as China, Japan, and The Korean Peninsula, for nearly 2,000 years. At present, their fermented products are widely used as food additives and nutraceutical supplements worldwide owing to their production of beneficial secondary metabolites. Heterotrimeric G-protein signaling pathways participate in regulating multiple biological processes in fungi. Previously, we identified three Monascus ruber M7 G-protein α subunits (Mga1–3) and demonstrated that Mga1 can regulate growth, reproduction and some secondary metabolites’ production. Here, we systematically analyzed and compared the roles of mga1–3 by combining single- and double-gene(s) knockouts and their transcriptomic data. First, mga2 and mga3 knock-out mutants and pairwise combinations of mga1–3 deletion strains were generated. Then the changes in growth, development and the main secondary metabolites, Monascus pigments and citrinin, in these mutants were systematically compared with M. ruber M7. Moreover, RNA-Seq analyses of these mutants were performed. All three Gα subunits worked together to regulate biological processes in M. ruber M7, with Mga1 playing a major role, while Mga2 and Mga3 playing supplemental roles. According to the existing literatures which we can find, gene knock-out mutants of the pairwise combination of mga1–3 and their transcriptome analysis are first reported in this study. The current results have clearly demonstrated the functional division of Mga1–3 in M. ruber M7, and could provide a deeper understanding of the effects of different Gα subunits on growth, development and secondary metabolism in other filamentous fungi.
Highlights
Monascus spp. have been used in food fermentation in Asian countries, such as China, Japan, and The Korean Peninsula, for nearly 2,000 years (Chen et al, 2015; Kim et al, 2016; Rahayu et al, 2017)
Mga1 and Mga2 can negatively regulate Monascus pigments (MPs) and CIT production individually or jointly, and Mga3 may work in combination with Mga1 to negatively enhance regulation of MPs production. These findings illuminate the functions of different Gα subunits in M. ruber M7 but could provide a deeper understanding of the effects of different Gα subunits on growth, development and secondary metabolism in other filamentous fungi
Single- and double-gene(s) deletion mutants of the three Gα subunits were first systematically analyzed to determine the effects of different Gα subunits on M. ruber M7 according to the phenotypic characteristics combined with RNA-Seq analyses
Summary
Monascus spp. have been used in food fermentation in Asian countries, such as China, Japan, and The Korean Peninsula, for nearly 2,000 years (Chen et al, 2015; Kim et al, 2016; Rahayu et al, 2017). The gene clusters of MPs, CIT and MK in Monascus spp. have been identified and their biosynthetic pathways have been fully illustrated (Chen et al, 2008; Li et al, 2015; He and Cox, 2016; Liu J. et al, 2016; Chen et al, 2017) The biosynthesis of these SMs cannot only be controlled by the intra-cluster regulating genes but can be adjusted by the off-cluster global regulating genes, such as LaeA, VeA, and related genes in the G-protein signaling pathway (GPSP) (Fox and Howlett, 2008; Liu Q. et al, 2016; Lin et al, 2018). GPSPs, including the G-protein coupled receptor (GPCR), heterotrimeric G-protein (G-protein) and downstream effectors (Seo and Yu, 2006), play vital roles in growth, differentiation, SMs biosynthesis, pathogenicity and toxicity in filamentous fungi (Yu et al, 2008; Corrochano et al, 2016; Moretti et al, 2017; Liu et al, 2018; van den Hoogen et al, 2018)
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