already identified key WRKY genes for developing blast- and bacterial blighttolerant plants in the future (Sureshkumar et al. 2019). The constitutive
overexpression of wild grapevine VdWRKY53 in Arabidopsis resulted in multi-fold
enhancement in resistance to multiple pathogens including P. syringae pv. tomato
(DC3000) (Zhang et al. 2019). More recently, Gao and group from Southwest
University of Science and Technology (China) characterized the role of SlWRKY8
in the resistance to P. syringae pv. tomato DC3000 (Pst DC3000) along with other
abiotic stresses. The constitutive overexpression in the tomato plants (Cv. Ailsa
Craig) resulted in increased resistance to Pst DC3000 by enhancing expression levels
of PR genes, namely SlPR1a1 as well as SlPR7. Overall, their report suggested the
role of SlWRKY8 in plant immunity against bacterial pathogen and other prominent
abiotic stresses (Gao et al. 2019).
11.5.3 Role of Host Plant WRKY Against Fungal Diseases
As described earlier, the WRKY TFs are one of a highly studied regulatory superfamily that plays a role in plant immunity (Singh et al. 2018b). Next to plant viruses,
the next major challenge to plant immunity is the onset of fungal diseases (Rahman
et al. 2019). There are already many reports in the literature by various research
groups for the bolstering support of the role of WRKY TFs against fungal diseases.
Out of all published articles, the first-ever preliminary report by Rushton et al. (1996)
used both gain- and loss-of-function experiments in parsley (Petroselinum crispum)
and identified the presence of WRKY1, WRKY2, and WRKY3 TFs binding W-box in
the promoters of PR1-1 and PR1-2 genes. Furthermore, they confirmed the Pep25
elicitor treatment in parsley cells induced a rapid increase in the mRNA levels of
only WRKY1 and WRKY3. Their work suggested that WRKY TFs might play a role
in the signal transduction pathway. The next published report came after a period of
long 3 years, i.e., in 1996, when the Euglem and colleagues published their in vivo
work in The EMBO Journal (Eulgem et al. 2000). They confirmed the parsley
WRKY1 acts as a transcriptional activator that mediates the Phytophthora sojae
elicitor-induced gene expression in parsley leaf tissue using in situ RNA
hybridization. In the same year, Suzuki from the National Institute of Bioscience
and Human-Technology (Japan) studied the signal transduction by inoculating two
elicitors, namely purified xylanase of Trichoderma viride and P. infestans cell wall
extract in the wild tobacco (Cv. Xanthi) cell suspension (Suzuki 1999). They
reported many regions including a putative EIRE that contained conserved motif
of W-boxes which might get activated by NtWRKY1, NtWRKY2, NtWRKY3, and
NtWRKY4 homologous to earlier reported parsley WRKYs. The effect of rice blast
fungus race KJ301-derived elicitor on the gene responsiveness in Asian rice
(Cv. Milyang 117) cell suspension culture cells was evaluated using cDNA library
screening and mRNA differential display. The results revealed the increase in the
cDNA levels of OsERG1, OsERG2, OsEREBP1, OsHin1, OsCPX1, OsLPL1,
OsMEK1 along with OsWRKY1 (Kim et al. 2008). Using suppression subtractive
hybridization (SSH), a putative StWRKY1 protein-encoding gene was identified in
348
L. S. Rajput et al.
overexpression of wild grapevine VdWRKY53 in Arabidopsis resulted in multi-fold
enhancement in resistance to multiple pathogens including P. syringae pv. tomato
(DC3000) (Zhang et al. 2019). More recently, Gao and group from Southwest
University of Science and Technology (China) characterized the role of SlWRKY8
in the resistance to P. syringae pv. tomato DC3000 (Pst DC3000) along with other
abiotic stresses. The constitutive overexpression in the tomato plants (Cv. Ailsa
Craig) resulted in increased resistance to Pst DC3000 by enhancing expression levels
of PR genes, namely SlPR1a1 as well as SlPR7. Overall, their report suggested the
role of SlWRKY8 in plant immunity against bacterial pathogen and other prominent
abiotic stresses (Gao et al. 2019).
11.5.3 Role of Host Plant WRKY Against Fungal Diseases
As described earlier, the WRKY TFs are one of a highly studied regulatory superfamily that plays a role in plant immunity (Singh et al. 2018b). Next to plant viruses,
the next major challenge to plant immunity is the onset of fungal diseases (Rahman
et al. 2019). There are already many reports in the literature by various research
groups for the bolstering support of the role of WRKY TFs against fungal diseases.
Out of all published articles, the first-ever preliminary report by Rushton et al. (1996)
used both gain- and loss-of-function experiments in parsley (Petroselinum crispum)
and identified the presence of WRKY1, WRKY2, and WRKY3 TFs binding W-box in
the promoters of PR1-1 and PR1-2 genes. Furthermore, they confirmed the Pep25
elicitor treatment in parsley cells induced a rapid increase in the mRNA levels of
only WRKY1 and WRKY3. Their work suggested that WRKY TFs might play a role
in the signal transduction pathway. The next published report came after a period of
long 3 years, i.e., in 1996, when the Euglem and colleagues published their in vivo
work in The EMBO Journal (Eulgem et al. 2000). They confirmed the parsley
WRKY1 acts as a transcriptional activator that mediates the Phytophthora sojae
elicitor-induced gene expression in parsley leaf tissue using in situ RNA
hybridization. In the same year, Suzuki from the National Institute of Bioscience
and Human-Technology (Japan) studied the signal transduction by inoculating two
elicitors, namely purified xylanase of Trichoderma viride and P. infestans cell wall
extract in the wild tobacco (Cv. Xanthi) cell suspension (Suzuki 1999). They
reported many regions including a putative EIRE that contained conserved motif
of W-boxes which might get activated by NtWRKY1, NtWRKY2, NtWRKY3, and
NtWRKY4 homologous to earlier reported parsley WRKYs. The effect of rice blast
fungus race KJ301-derived elicitor on the gene responsiveness in Asian rice
(Cv. Milyang 117) cell suspension culture cells was evaluated using cDNA library
screening and mRNA differential display. The results revealed the increase in the
cDNA levels of OsERG1, OsERG2, OsEREBP1, OsHin1, OsCPX1, OsLPL1,
OsMEK1 along with OsWRKY1 (Kim et al. 2008). Using suppression subtractive
hybridization (SSH), a putative StWRKY1 protein-encoding gene was identified in
348
L. S. Rajput et al.