Biomedical Engineering Reference
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of cuticle. The
Pr1
and
Pr2
genes were also highly expressed on cuticle
media in
B. bassiana
(Khan et al. 2007, Donati 2008, Dias et al. 2008). The
promoter of the gene encoding PR1 of
M. anisopliae
contains putative
binding sites for regulatory proteins similar to carbon-catabolite repressor
(CREA) (Screen et al. 1997), nitrogen metabolite regulator (AREA) and
the eukaryotic CREB (Clarkson and Charnley 1996). It is activated by low
nitrogen levels and switched off once the hyphae reach the nitrogen rich
hemolymph.
M. anisopliae
was found to have more (132) genes encoding secreted
proteases than other sequenced fungi (Gao et al. 2011).There are 32 genes
coding for proteases degrading trypsin, 33 genes coding for aspartyl
proteases and 55 genes coding for subtilisins in the genome of
M. anisopliae
(Gao et al. 2011). Subtilisins have been found to assist in the infection
processes of
M. anisopliae
by degrading host cuticles, providing nutrition
and disabling antimicrobial peptides (Bagga et al. 2004). The importance
of aspartyl proteinases has not been demonstrated in
M. anisopliae
but
fungi resemble the aspartyl proteases that assist the human pathogen
C.
albicans
by degrading cell surface molecules (Schaller et al. 2005). In spite
of the abundance of protease genes in the
Metarhizium
genome only a few
proteases mostly the trypsins were found to be expressed in the early stages
of infection (Gao et al. 2011). Trypsins are implicated in suppression of host
defences (Gao et al. 2011). The ESTs from the cDNA library of
M. anisopliae
cultures grown on insect cuticle consisted of abundant number constituting
25% of the ESTs that coded for diverse proteases (Wang et al. 2005). Eight
subtilisin genes were expressed on the cuticle medium in
M. anisopliae
(Bagga et al. 2004, Freimoser et al. 2003). Pr1H was found to be differentially
expressed in
B. bassiana
cultured on insect cuticles being expressed on
cuticles of
Spodoptera litura
larvae and
Epilachna vigintioctopunctata
but not
on cuticles of
Aphis craccivora
and
Periplaneta americana
(Khan et al. 2007).
An EST homologous to membrane-bound methionine aminopeptidase
(MAP) enzyme of metalloprotease family was detected in
B. bassiana
cultured on
Aphis craccivora
but not on cuticles of
Spodoptera litura
larvae,
Epilachna vigintioctopunctata
and
Periplaneta americana
(Khan et al.
2007). A serine protease bassiasinI was reported in
B. bassiana
(Kim et al.
1999).
In
M. anisoplieae
cultured on cuticle medium, genes with homologues
involved in amino acid catabolism—glutaminase A and NADH-specifi c
glutamate dehydrogenase were found up regulated (Freimoser et al. 2005).
Glutamate is reported as the preferred substrate for
M. anisopliae.
Genes homologous to those coding for transport of di-/tripeptides and
tetra-penta peptides and diverse amino acid transporters were found up
regulated in
M. anispoliae
cultured on cuticle medium (Freimoser et al. 2005).
