Biomedical Engineering Reference
In-Depth Information
the fumonisin cluster is specifi c for
G. moniliformis
(teleomorph of
F.
verticillioides
) and the patulin genes have been obtained from
Penicillium
expansum
. The microarray is designed in a way that newly identifi ed
pathway genes can be added easily at any time. The microarray was used
to detect the activation of all gene clusters under conditions conducive
for mycotoxin biosynthesis and to demonstrate differences in mycotoxin
pathway gene expressions after growth on various media for trichothecene
and ochratoxinA biosynthesis. It was used further to study and compare
the expression kinetics of the trichothecene biosynthesis genes of
Fusarium
on different trichothecene supporting media. An expression pattern
indicative for trichothecene biosynthesis could be identifi ed.
CONCLUSION
Diagnostic PCR based systems are now available for all of the relevant
toxigenic fungi. During the last decade the genes that are involved in the
biosynthesis and regulation of mycotoxin production were identifi ed and
the sequence data made available. Various PCR based systems developed
targeting these relevant genes were largely based on the motivation of
perspective studies for using this kind of analysis to forecast the presence
and concentrations of mycotoxins in sample materials. One might
therefore, anticipate that assays based on mycotoxin biosynthetic genes
might better fi t that purpose as compared to systems based on genes
unrelated to their biosynthesis. However, only in a few cases, correlation
between presence of a PCR signal or its intensity and incidence or
concentrations of certain mycotoxins have been analyzed and in certain
cases a positive correlation has been established. Biosynthesis of most
mycotoxins is a highly complex process with poorly understood regulation
at the transcriptional level which is also infl uenced by environmental
factors. Therefore, it seems unlikely to fi nd a highly positive correlation
between amplifi cation signal and concentrations of compounds. Only in
few cases such a correlation has been established with quantitative real-
time PCR on mycotoxin biosynthesis genes (Schnerr et al. 2002, Ramana et
al. 0211). Similarly, a reasonable correlation between results of quantitative
real-time PCR and mycotoxin concentrations were found when primers
were targeted to anonymous sequences (Waalwijk et al. 2004b, Leisova et
al. 2006) or to sequences of housekeeping genes (Mule et al. 2006).
Prediction of mycotoxin concentrations using a PCR and RT-PCR
based systems were unlikely to work in a way that would allow for this
technique to replace analysis of mycotoxins unless assays are developed
that are based on expression of genes involved in mycotoxin biosynthesis,
i.e. systems using cDNA as target for amplifi cation. The microarray system
developed recently by R. Geisen's group at the Federal Institute for Nutrition
