Biomedical Engineering Reference
In-Depth Information
Application of ATMT Method for Identifying
Pathogenicity Genes
Many fungal pathogens have evolved mechanisms to expand their host
range and overcome various surface barriers encountered during the
infection cycle (Oliver and Osbourn, 1995, Knogge 1998, Dean 1997,
Idnurm and Howlett 2001). In a majority of the fungal pathogens,
only a few genes required for pathogenicity have been identifi ed and
characterized, including
M. oryzae
and
V. dahliae
(Talbot 2003, Gao et al. 2011,
Maruthachalam et al. 2011a). These studies offer many benefi ts not only to
the scientifi c community but also the society at large. The characterization
of pathogenicity genes while increasing our overall understanding of the
disease processes would also potentially identify genes that could become
targets for disease control strategies. Identifi cation and characterization of
candidate genes can be classifi ed into two broad categories: forward and
reverse genetic approaches. Forward genetic approaches such as random
insertional mutagenesis provide a unique opportunity to generate genetic
mutations in a manner that facilitates subsequent isolation of mutated
genes (Michielse et al. 2005, Jeon et al. 2007). Therefore, the genetic
transformation technology has been considered integral to the study of
fungal pathogenicity genes at the molecular level, either creating targeted
or random insertional mutagenesis. From the developed mutant library,
mutants with specifi c process defi ciency can be searched to identify the
mutants of interest. Subsequently, the identifi cation of mutated gene and
verifi cation that the observed phenotypes are the result of disrupted gene
may reveal its function. Using this approach, it is possible to identify and
characterize the several unknown gene functions in many economically
important fungi.
Identifi cation and Characterization of Genes in
V. dahliae
In
V. dahliae
, the genes responsible for pathogenicity and microsclerotial
development are less understood and only a few genes required for
microsclerotial development and pathogenicity have been characterized
using ATMT
(Table 2)
.
The involvement of these genes in different stages
of disease development has been reported (Wang et al. 2004, Rauyaree et
al. 2005, Klimes and Dobinson 2006, Tzima et al. 2010).
The
V. dahliae
VMK1
gene, a gene encoding a mitogen-activated
protein (MAP) kinase was functionally characterized and the disruption of
VMK1
gene led to reduced virulence of this fungus on lettuce and tomato
plants (Rauyaree et al. 2005). In addition,
vmk1
mutants showed reduced
conidiation and microsclerotia formation. These results suggest that
VMK1
