3.1 Loss of antitumor activity in an AaLaeAOE26
To clarify the status of A549 cells, the assay was performed with
adriamycin as the positive drug. The results found the
IC50 of adriamycin against A549 was 2.63 μg/mL, which is
consistent with the literature [23]. It showed that the A549 cell
line was in normal condition and could be used for the experiment (Fig.
1A). Overexpression of the global regulator AaLaeA in Alternaria
alstroemeria led to two contrasting antitumor activities in
overexpressed transformants. Among them, the transformantAaLaeA OE29 showed increased antitumor activity
[24], while AaLaeA OE26 completely lost its
antitumor activity (Fig. 1B). The crude extract of the wild-type strain
of A. alstroemeria showed significant inhibition of A549 cells,
with the relative inhibition rate in a concentration-dependent manner.
At a concentration of 300 μg/mL, the inhibition rate reached 33.43 %
and the IC50 value was 328 μg/mL. This indicated that
the crude extract of the wild-type strain had a significant inhibitory
effect on A549 (Fig. 1B). The insertion site ofAaLaeA OE26 was analyzed via genome
resequencing, and the results showed that the insertion site ofAaLaeA OE26 was in the non-coding region.
Therefore, we suggest that the insertion of AaLaeA did not
destruct other genes (Fig. S1). The data showing the loss of antitumor
activity of AaLaeA OE26 was caused by the
expression of AaLaeA, and there may be a quantitative-effect
relationship between AaLaeA expression and antitumor activity.