The expression of PatL, encoding the putative transcription factor
of patulin biosynthesis cluster (Li et al., 2015), was analyzed in
P. expansum T01 under different C, N and pH conditions using RT-qPCR.
Under C sources which favored patulin production, such as glucose, sucrose
and maltose, the expression level of PatL was up-regulated. In contrast, PatL expression was down-regulated under C sources of cellulose
and malic acid which did not support patulin production (Fig. 4A).
Similarly the expression of PatL was up-regulated in media supplemented
with peptone, beef extract, glutamic acid and yeast extract, and
down-regulated with urea and ammonium sulfate as the sole N source
(Fig. 4B). The highest expression level of PatL presented at pH 4 followed
by pH 5