Biomedical Engineering Reference
In-Depth Information
ammonia, aspirin, copper, manganese, osmotin, pheromones, viral killer
toxins, hyperosmotic stress and expression of mammalian Bax and Bak
which belong to B-cell lymphoma 2 family proteins. To date
Candida albicans
,
Fusarium oxysporum
,
Aspergillus fumigatus
and
Aspergillus nidulans
have
also been reported to undergo apoptosis upon exposure to some but not
all of these inducers (Ludovico et al. 2001, 2002, Mousavi and Robson 2004,
Reiter et al. 2005, Semighini et al. 2006, Ito et al 2007, Phillips et al. 2003,
Zheng et al. 2007, Pozniakovsky et al. 2005, Váchová et al. 2004, Balzan et
al. 2004, Liang et al. 2007, Ligr et al. 1998, De Smet et al. 2004, Silva et al.
2005, Narisimhan et al. 2001).
Some of these apoptotic inducers may play an important role
in the treatment of fungal infections in both humans and plants. An
advantage of some of these inducers is the evidence that they target
the infecting fungal pathogen only and the host remains unaffected. In
the 2008 review by Hamann and colleagues, it was documented that
neither the antifungal proteins PAF nor AFP (an antifungal protein
produced by the fungus
Aspergillus giganteus
) exhibit detrimental effects
on mammalian cells. Another advantage of these treatments is that they
are not species specifi c so they have the potential to inhibit growth of many
different fungi.
In order to target fungal metacaspases with a view to developing
therapeutic or antifungal or indeed biocontrol agents, the role of
metacaspases in apoptotic PCD in fungi requires further study. All PCD
pathways involving metacaspases are still not fully elucidated, but with
continued research it is becoming more apparent that metacaspases play
an important part. Gene mutation and knockout studies are useful tools
to analyse the functions of fungal metacaspases. One such study was the
deletion of two metacaspase genes PaMca1 and PaMca2 in
Podospora anserine
.
This experiment resulted in an increase in mean lifespan, indicating that the
PaMca1 and PaMca2 genes are required in the apoptotic machinery of the
organism (Hamann et al. 2007, Scheckhuber et al. 2007). It was also noted
that deletion of PaMca1 desensitised the apoptotic response of the fungus
when exposed to etoposide, an inducer of apoptosis. It was also reported
that strains with the deleted PaMca1 gene displayed higher viability than
wild type strains (Hamann et al. 2007, Scheckhuber et al. 2007).
Further studies with Yca1p, the single metacaspase gene encoded
by the genome of
Saccharomyces cerevisiae
which is cleaved like a typical
caspase in response to oxidative stress (Madeo et al. 2002) also points to the
hypothesis that metacaspases play an important role in PCD. Research by
several groups including Madeo et al. 2002, Bettiga et al. 2004, Herker et al.
2004, Wadskog et al. 2004, Flower et al. 2005, Khan et al. 2005, Mazzoni et al.
2005, Reiter et al. 2005, Silva et al. 2005 and Weinberger et al. 2005 support
