confirmed that CaWRKY-a might be involved as a transcription factor in defenserelated signal transduction pathway against TMV (P1.2 pathotype). The positive
regulatory roles of CaWRKY1 and CaWRKY2 against the deadly viruses, namely
TMV and Pepper mild mottle virus were first put up forwarded by Oh and colleagues
in their series of publications, respectively (Oh et al. 2006). In another published
report, Dardick from Appalachian Fruit Research Station focused on identifying the
statistically significant changes in gene expression concomitant with Plum pox
potyvirus (PPV), Tomato ringspot nepovirus (ToRSV), and Prunus necrotic
ringspot ilarvirus (PNRSV) symptoms in N. benthamiana leaves. The expression
levels of identified WRKY transcription factors are in accordance with the severity
of the observed symptoms in all three viruses (Dardick 2007). In another report,
overexpression of four Medicago truncatula MtWRKY genes in the tobacco confirmed their regulatory roles in upregulating PR genes expression as well as lignin
deposition against TMV (Naoumkina et al. 2008). Similarly, Babu et al. (2008)
focused on the global gene expression using Arabidopsis Affymetrix ATH1 array
after PPV infection in protoplasts of Arabidopsis accession Col-0. In this study, the
263 genes were upregulated including family members of WRKY TF, MADS-box
protein, TIR-NBS-LRR, and zinc-finger family protein. In a similar study,
McGregor and colleagues focused on one of the most devastating Ipomoea batatas
disease, namely sweet potato virus disease. They used a similar global gene expression approach in two different sweet potato cultivars NASPOT1 (resistant) and
Beauregard (susceptible). Their group found that cell expansion genes, as well as
chloroplastic genes, were suppressed, while stress-related and various transcription
family genes (WRKY, homeodomain proteins, and NAC-like proteins) were
induced highly. After virus infection, the protein synthesis-related genes induction
was in co-relation with virus accumulation in susceptible plants. This switch in the
expression of all these specific host-encoded genes was established as a reason to
cause developmental defects in susceptible plants (McGregor et al. 2009). In another
publication, Alfenas-Zerbini and his Brazilian colleagues inoculated susceptible
plants of tomato (Cv. Moneymaker) with Pepper yellow mosaic virus and further
constructed a subtractive library from inoculated leaves at 72 h after inoculation. The
upregulated genes were identified to be related to stress/defense response, cell cycle
regulation, signal transduction, and transcriptional regulation (e.g., WRKY22 and
SCARECROW TF). Few of the differentially expressed genes (DEGs) including
WRKY22 were validated using macroarray analysis (Alfenas-Zerbini et al. 2009). In
the year 2009, an Italian group headed by Catoni elucidated the organ-specific
responses upon Tomato spotted wilt virus (TSWV) infection at the transcriptional
level. They reported a total of 17 WRKY TFs were found differentially expressed in
shoots and roots (Catoni et al. 2009). Similarly, the antiviral role of tobacco
NtWRKY4 in viral stress tolerance was affirmed by using RNAi technology. Upon
TMV inoculation, the mosaic pattern leaves were highly twisted in the transgenic
plants as compared to the uninoculated wild-type (Ren et al. 2010). Chen and Yeh
(2010) used a microarray assay to analyze the effect of TMV infection on A. thaliana
protoplasts. They affirmatively reported that approximately eight transcriptional
regulation genes showed greater than threefold changed expression. Furthermore,
342
L. S. Rajput et al.
regulatory roles of CaWRKY1 and CaWRKY2 against the deadly viruses, namely
TMV and Pepper mild mottle virus were first put up forwarded by Oh and colleagues
in their series of publications, respectively (Oh et al. 2006). In another published
report, Dardick from Appalachian Fruit Research Station focused on identifying the
statistically significant changes in gene expression concomitant with Plum pox
potyvirus (PPV), Tomato ringspot nepovirus (ToRSV), and Prunus necrotic
ringspot ilarvirus (PNRSV) symptoms in N. benthamiana leaves. The expression
levels of identified WRKY transcription factors are in accordance with the severity
of the observed symptoms in all three viruses (Dardick 2007). In another report,
overexpression of four Medicago truncatula MtWRKY genes in the tobacco confirmed their regulatory roles in upregulating PR genes expression as well as lignin
deposition against TMV (Naoumkina et al. 2008). Similarly, Babu et al. (2008)
focused on the global gene expression using Arabidopsis Affymetrix ATH1 array
after PPV infection in protoplasts of Arabidopsis accession Col-0. In this study, the
263 genes were upregulated including family members of WRKY TF, MADS-box
protein, TIR-NBS-LRR, and zinc-finger family protein. In a similar study,
McGregor and colleagues focused on one of the most devastating Ipomoea batatas
disease, namely sweet potato virus disease. They used a similar global gene expression approach in two different sweet potato cultivars NASPOT1 (resistant) and
Beauregard (susceptible). Their group found that cell expansion genes, as well as
chloroplastic genes, were suppressed, while stress-related and various transcription
family genes (WRKY, homeodomain proteins, and NAC-like proteins) were
induced highly. After virus infection, the protein synthesis-related genes induction
was in co-relation with virus accumulation in susceptible plants. This switch in the
expression of all these specific host-encoded genes was established as a reason to
cause developmental defects in susceptible plants (McGregor et al. 2009). In another
publication, Alfenas-Zerbini and his Brazilian colleagues inoculated susceptible
plants of tomato (Cv. Moneymaker) with Pepper yellow mosaic virus and further
constructed a subtractive library from inoculated leaves at 72 h after inoculation. The
upregulated genes were identified to be related to stress/defense response, cell cycle
regulation, signal transduction, and transcriptional regulation (e.g., WRKY22 and
SCARECROW TF). Few of the differentially expressed genes (DEGs) including
WRKY22 were validated using macroarray analysis (Alfenas-Zerbini et al. 2009). In
the year 2009, an Italian group headed by Catoni elucidated the organ-specific
responses upon Tomato spotted wilt virus (TSWV) infection at the transcriptional
level. They reported a total of 17 WRKY TFs were found differentially expressed in
shoots and roots (Catoni et al. 2009). Similarly, the antiviral role of tobacco
NtWRKY4 in viral stress tolerance was affirmed by using RNAi technology. Upon
TMV inoculation, the mosaic pattern leaves were highly twisted in the transgenic
plants as compared to the uninoculated wild-type (Ren et al. 2010). Chen and Yeh
(2010) used a microarray assay to analyze the effect of TMV infection on A. thaliana
protoplasts. They affirmatively reported that approximately eight transcriptional
regulation genes showed greater than threefold changed expression. Furthermore,
342
L. S. Rajput et al.