Fig.3-4 Colony phenotypes of C100, ΔMareA and
OE-MareA in different nitrogen sources media
3.2.2 Colony diameter analysis
On PDA medium, the growth of the knockout strain ΔMareA was
significantly inhibited, with its colony diameter only 33.5% of that of
the original strain C100. In contrast, the overexpression strain
OE-MareA exhibited faster growth. This indicates that theAreA gene has an impact on the growth and development of C100. On
PDA-Gln medium, all three strains showed a faster and essentially equal
growth rate, suggesting that Gln as a nitrogen source can compensate for
the effect of the AreA gene on C100 growth and development.
However, when (NH4)2SO4was added in the PDA medium, ΔMareA strain’s ability to utilize
it was significantly reduced, consistent with findings inPenicillium oxalicum (Rabha and Jha, 2018). In
PDA-NaNO3 medium, ΔMareA strain exhibited poor
utilization of this nitrogen source resulting in slowed down growth
rate; whereas OE-MareA strain was not affected due to presence ofMareA gene and showed slightly higher growth rate than C100. In
PDA-Urea medium, ΔMareA strain’s growth was higher compared to
NaNO3. Overall, the MareA gene had a significant
impact on monascus’ growth rate. Furthermore,the MareA gene also
plays an important regulatory role in utilizing different nitrogen
sources. The function of MareA gulatory varies among different
fungi,which demonstrates diversity in regulatory functions performed by
the MareA gene. As shown in Figure 3-5.
Fig.3-5 Colony diameters of C100, ΔMareA and
OE-MareA in PDA medium with different nitrogen addition
3.2.3 Analysis of conidial production
The conidial yield of the knockout strain ΔMareA on PDA medium
was significantly lower than that of the original strain C100, while the
spore yield of the overexpression strain increased. The spore production
of ΔMareA was relatively high on PDA-Gln medium, while it was the
least on PDA-NaNO3 medium. The spore production of the
overexpression strain OE-MareA was higher than that of the
original strain C100 on PDA-Gln, PDA-NaNO3, and PDA-Urea
media, while it was lower than that on
PDA-(NH4)2SO4 media. It
is speculated that a higher concentration of ammonium salt would inhibit
conidial production in O E-MareA . In summary, theMareA gene affects monascus’ conidial production by inhibiting it
when deleted and increasing it when overexpressed. Additionally, there
is a difference in how MareA gene utilizes different nitrogen
sources: Gln as a nitrogen source can offset AreA gene’s effect
on conidia to some extent, while NaNO3 has the greatest
impact on Monascus . As shown in Figure 3-6.