| Summary: | Blue light, as an important environmental factor, can regulate the production of various secondary metabolites of <i>Monascus purpureus</i> M9, including mycotoxin-citrinin, pigments, and monacolin K. The analysis of citrinin in <i>Monascus</i> M9 exposed to blue light for 0 min./d, 15 min./d, and 60 min./d showed that 15 min./d of blue light illumination could significantly increase citrinin production, while 60 min./d of blue light illumination decreased citrinin production. Analysis of long non-coding RNA (LncRNA) was performed on the transcripts of <i>Monascus</i> M9 under three culture conditions, and this analysis identified an lncRNA named <i>AOANCR</i> that can negatively regulate the <i>mraox</i> gene. Fermentation studies suggested that alternate respiratory pathways could be among the pathways that are involved in the regulation of the synthesis of citrinin by environmental factors. Aminophylline and citric acid were added to the culture medium to simulate the process of generating cyclic adenosine monophosphate (cAMP) in cells under illumination conditions. The results of the fermentation showed that aminophylline and citric acid could increase the expression of the <i>mraox</i> gene, decrease the expression of lncRNA <i>AOANCR</i>, and reduce the yield of citrinin. This result also indicates a reverse regulation relationship between lncRNA <i>AOANCR</i> and the <i>mraox</i> gene. A blue light signal might regulate the <i>mraox</i> gene at least partially through lncRNA <i>AOANCR</i>, thereby regulating citrinin production. Citrinin has severe nephrotoxicity in mammals, and it is important to control the residual amout of citrinin in red yeast products during fermentation. LncRNA <i>AOANCR</i> and <i>mraox</i> can potentially be used as new targets for the control of citrinin production.
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