(Strain DC300) infiltration on mature leaves resulted in AtWRKY6 induced expression which implicated the role of AtWRKY6 in regulating a few aspects of host
defense response (Robatzek and Somssich 2001).
In one of their article in series, Robatzek and Somssich studied the targets of
senescence- and defense-associated AtWRKY6 factors. Their study revealed the
WRKY6 negative regulation on its promoter activity as well as promoters of
AtPR1, AtSIRK, and other closely related WRKY family members (Robatzek and
Somssics 2002). The AtWRKY18 was overexpressed under the control of CaMV35S
promoter in Arabidopsis which results in stunting, increased levels of PR genes as
well as resistance against P. syringae in the transgenic plants (Chen and Chen 2002).
Dong and colleagues identified a list of common AtWRKYs induced under treatments
such as SA application as well as inoculation of an avirulent strain of P. syringae
(Dong et al. 2003).
The OsWRKY03 transcript profile in rice seedlings specifically varies with treatment such as hormones, fungicide, rice bacterial blight pathogen, and mechanical
wounding (Liu et al. 2005). In X. oryzae pv. oryzae infected rice plants, systematic
expression analysis revealed that 12 OsWRKYs-encoding genes were differentially
regulated including OsWRKY-7, OsWRKY-10, OsWRKY-11, OsWRKY-30,
OsWRKY-32, OsWRKY-67, OsWRKY-70, OsWRKY-83, and OsWRKY-85 (Ryu
et al. 2006). Similarly, using a domain-specific differential display procedure, Park
et al. (2006) isolated a rapidly induced WRKY gene, namely CaWRKY-a during
X. campestris pv. vesicatoria infection (Park et al. 2006). Similarly, the positive role
of nuclear-localized AtWRKY7 gene in P. syringae susceptibility was confirmed
using loss- and gain-of-function studies in A. thaliana (Kim et al. 2006). Similarly,
the negative role of the AtWRKY25 in plant defense against the bacterial pathogen
P. syringae was also deduced using T-DNA insertion mutants and overexpression
studies (Zheng et al. 2007).
The complexity of the CaWRKY1 networking in chili pepper leaves was studied
upon inoculation of X. axonopodis pv. vesicatoria and P. syringe pv. tabaci using
VIGS and overexpression technology. Their work suggested that CaWRKY1 got
strongly induced upon bacterial inoculation (Oh et al. 2008). In another study, the
rice OsWRKY45 expression was highly upregulated upon treatments such as ABA,
NaCl, PEG, heat stress, cold stress, blast pathogen as well as rice bacterial blight
pathogen. Furthermore, OsWRKY45 over expressed plants showed increase in PR
genes’ expression as well as enhaced tolerance/resistance to P. syringae, salt and
drought stresses (Qiu and Yu 2009). In another instance, the AtWRKY8 induction
was observed upon various treatments such as maggot infestation, ABA, H2O2,
wounding as well as P.syringae infection. Furthermore, T-DNA insertion mutants
showed increased resistance to P. syringae, whereas OE AtWRKY8 transgenic plants
displayed an increase in susceptibility to the might bacteria P. syringae infection.
Combined, the study suggested that AtWRKY8 acts as a negative regulator to
P. syringae resistance (Chen et al. 2010).
Hwang and colleagues firstly isolated a group II OsWRKY6 from rice samples
infected with X. oryzae pv. oryzae. Furthermore, their heterologous overexpression
study in Arabidopsis confirmed OsWRKY6 acts as a transcriptional regulator of the
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L. S. Rajput et al.
defense response (Robatzek and Somssich 2001).
In one of their article in series, Robatzek and Somssich studied the targets of
senescence- and defense-associated AtWRKY6 factors. Their study revealed the
WRKY6 negative regulation on its promoter activity as well as promoters of
AtPR1, AtSIRK, and other closely related WRKY family members (Robatzek and
Somssics 2002). The AtWRKY18 was overexpressed under the control of CaMV35S
promoter in Arabidopsis which results in stunting, increased levels of PR genes as
well as resistance against P. syringae in the transgenic plants (Chen and Chen 2002).
Dong and colleagues identified a list of common AtWRKYs induced under treatments
such as SA application as well as inoculation of an avirulent strain of P. syringae
(Dong et al. 2003).
The OsWRKY03 transcript profile in rice seedlings specifically varies with treatment such as hormones, fungicide, rice bacterial blight pathogen, and mechanical
wounding (Liu et al. 2005). In X. oryzae pv. oryzae infected rice plants, systematic
expression analysis revealed that 12 OsWRKYs-encoding genes were differentially
regulated including OsWRKY-7, OsWRKY-10, OsWRKY-11, OsWRKY-30,
OsWRKY-32, OsWRKY-67, OsWRKY-70, OsWRKY-83, and OsWRKY-85 (Ryu
et al. 2006). Similarly, using a domain-specific differential display procedure, Park
et al. (2006) isolated a rapidly induced WRKY gene, namely CaWRKY-a during
X. campestris pv. vesicatoria infection (Park et al. 2006). Similarly, the positive role
of nuclear-localized AtWRKY7 gene in P. syringae susceptibility was confirmed
using loss- and gain-of-function studies in A. thaliana (Kim et al. 2006). Similarly,
the negative role of the AtWRKY25 in plant defense against the bacterial pathogen
P. syringae was also deduced using T-DNA insertion mutants and overexpression
studies (Zheng et al. 2007).
The complexity of the CaWRKY1 networking in chili pepper leaves was studied
upon inoculation of X. axonopodis pv. vesicatoria and P. syringe pv. tabaci using
VIGS and overexpression technology. Their work suggested that CaWRKY1 got
strongly induced upon bacterial inoculation (Oh et al. 2008). In another study, the
rice OsWRKY45 expression was highly upregulated upon treatments such as ABA,
NaCl, PEG, heat stress, cold stress, blast pathogen as well as rice bacterial blight
pathogen. Furthermore, OsWRKY45 over expressed plants showed increase in PR
genes’ expression as well as enhaced tolerance/resistance to P. syringae, salt and
drought stresses (Qiu and Yu 2009). In another instance, the AtWRKY8 induction
was observed upon various treatments such as maggot infestation, ABA, H2O2,
wounding as well as P.syringae infection. Furthermore, T-DNA insertion mutants
showed increased resistance to P. syringae, whereas OE AtWRKY8 transgenic plants
displayed an increase in susceptibility to the might bacteria P. syringae infection.
Combined, the study suggested that AtWRKY8 acts as a negative regulator to
P. syringae resistance (Chen et al. 2010).
Hwang and colleagues firstly isolated a group II OsWRKY6 from rice samples
infected with X. oryzae pv. oryzae. Furthermore, their heterologous overexpression
study in Arabidopsis confirmed OsWRKY6 acts as a transcriptional regulator of the
346
L. S. Rajput et al.