Biomedical Engineering Reference
In-Depth Information
have been designed and can be used in conjunction with assays for either
tri5
or
tri4
as part of a robust detection system for trichothecene producers.
The
tri5
gene encodes trichodiene synthase, which catalyses the fi rst step in
the trichothecene biosynthetic pathway (Fig. 4) and this gene has also been
targeted for the production of primers specifi c to trichothecene producers.
The trichothecene biosynthetic pathway (Fig. 4), begins with the cyclization
of the isoprenoid biosynthetic intermediate farnesyl pyrophosphate to
trichodiene by the enzyme trichodiene synthase. The pathway subsequently
involves a number of oxygenations, isomerizations, cyclizations and
esterifi cations leading from trichodiene to diacetoxyscirpenol, T-2 toxin
and 3-acetyldeoxynivalenol. The pathway has largely been elucidated
through whole cell feeding experiments and mutant characterization on
a number of
Fusarium
species (Desjardins et al. 1993). The initial enzyme
in the pathway, trichodiene synthase has been purifi ed and consists of a
homodimer with a subunit of 45 kDa (Hohn and Van Middlesworth 1986).
The isolation of other biosynthetic enzymes has proven more diffi cult,
although cytochrome P- 450 monooxygenases are known to be involved
(Gledhill et al. 1991).
Figure 4.
Fusarium
trichothecene biosynthetic pathway. Genes involved [A]
Tri
5, [B]
Tr i
4 and [C]
Tri
3. (Compiled from Desjardins et al. 1993 and Proctor et al. 1995)
