Biomedical Engineering Reference
In-Depth Information
Figure 10.
Detection of ochratoxin producing fungi targeting PKS gene primres were
used (AOLC35 12l/12R) (Doe, et al. 2005). Lane1- 1 kb DNA lader, 1- negative control,
lane 2-4- OTA producing
Aspergillus,
Lane 5&6 OTA positive strains of
Penicillim
spp.
b) Fungi producing Ochratoxins
Ochratoxins are the carcinogenic compounds produced by
Aspergillus
and
Penicillium
species. Among the ochratoxins produced by
Aspergillus
and
Penicillium
spp., ochratoxin A (OTA) is the prominent carcinogenic
mycotoxin. Biosynthetically OTA is a pentaketide derived from the
dihydrocoumarin family coupled to β-phenylalanine. Its chemical name
is: L-phenylalanine-
N
-[(5-chloro-3,4-dihydro-8-hydroxy-3-methyl-1-oxo-
1
H
-2-benzopyrane-7-yl)carbonyl] -(
R
)-isocoumarin.
Callaghan et al
.
2006 attempted to identify putative OTA biosynthetic
genes in
A. ochraceus
by comparing their expression profi les with that of
the OTA
pks
gene in permissive and restrictive medium. In their study, they
focused on two putative cytochrome P450 monooxygenase genes. Both
genes displayed a high degree of similarity to other monooxygenase genes
encoding enzymes involved in the biosynthesis of polyketide secondary
metabolites. Specifi cally, the p450-H11 gene is very similar to the averantin
oxidoreductase gene involved in afl atoxin biosynthesis (Yu et al. 1997), while
the p450-B03 gene is not only similar to the trichodiene oxygenase gene
from the trichothecene biosynthetic pathway in
Gibberella zeae
(Ward et al.
2002) but also displays signifi cant similarity to the
cyp
A gene in the afl atoxin
biosynthetic pathway from
A. fl avus
(Ehrlich et al. 2004). The
pks
gene
characterized by Callaghan et al. 2003, shares more than 98% identity with
a PKS gene
awlc35-12
(or
aolc35-12)
, identifi ed in
A. westerdijkiae
(Atou et al.
2006, Dao
et al.
2005). Dao et al. 2005, designed two sets of specifi c primers,
AoLC35-12L/AoLC35-12R and AoOTAL/AoOTAR, from AoLC35-12, the
set primers AoOTAL/AoOTAR specifi cally detected
A. ochraceus
by PCR
