Abstract: mok E gene belongs to the Monacolin K biosynthesis gene cluster, whose expression level is positively correlated with Monacolin K production. In this research, mok E gene was overexpressed in Monascus M1 and its expression level was measured by reverse transcription-quantitative real-time polymerase chain reaction (RT-qPCR). The Monacolin K production in transformants was measured by high performance liquid chromatography (HPLC). The morphological features of mycelia and spore of the wild-type strain and the transformants were observed by scanning electron microscope (SEM). The results showed that 240 transformants were obtained by hygromycin resistance selection. Nine of these transformants were selected for the measurement of mok E expression by RT-qPCR. The expression levels of mok E gene were enhanced in three transformants, T2, T8 and T9. The production rates of Monacolin K lactone in transformants T2, T8 and T9 were 2 159.7, 4 177.6, and 3 365.7 μg/g, respectively, which were increased by 49.2%, 188.5% and 132.5%, respectively, compared with that in the wild-type strain (1 447.8 μg/g). The results of SEM revealed that mok E overexpression contributed to the morphological changes of mycelia and spore.

Key words: Monascus spp., overexpression, Monacolin K, reverse transcription-quantitative real-time polymerase chain reaction (RT-qPCR), scanning electron microscope (SEM), spore