11.4.6 Small RNA Regulation
Small RNAs (smRNA) regulate WRKY TFs under pathogen response by RNA
interference, RNA silencing, or post-transcriptional gene silencing (PTGS) (Voinnet
2009). After several phytohormone treatments in rice, several miRNAs were
induced; out of which, miR167f encoded an NBS-LRR disease resistance protein
(Liu et al. 2009). Double mutants of Atwrky18 Atwrky40 provide resistance to G.
orontii by enhaning the expression of RCD One5 (SRO5) which allows siRNA
production and leads to suppression of WRKY TFs (Borsani et al. 2005). Similarly,
AvrPtoB an effector secreted by P. syringae protein suppresses host miRNAs which
lead to suppression of AtWRKY30 (Navarro et al. 2008). Production of secondary
metabolites can be regulated by miRNA which provides resistance against fungi.
Expression profiling of apple (Cv. Golden Delicious) infected with leaf spot fungus
(A. alternata f. sp. mali.) confirmed that both Md-miR156ab and MdmiR395 target
MdWRKYN1 and MdWRKY26, respectively, and regulate resistance against the
pathogen (Zhang et al. 2017). After the inoculation of F. oxysporum in Persicaria
minor (a herb), the miRNAs get upregulated and downregulated by the WRKY TFs
and terpenoid biosynthesis was reduced (Samad et al. 2019).
11.5 Role of WRKY TFs Against Phytopathogens
11.5.1 Role of Host Plant WRKY Against Viral Diseases
As described earlier, the WRKY TFs are one of the highly studied regulatory protein
family which play both positive and negative role in plant immunity (Chen et al.
2019). One of the major challenges to plant immunity is the onset of viral diseases
(Honjo et al. 2020). There are already many reports in the literature by various
research groups for the bolstering support of the role of WRKY TFs against plant
viruses. Out of all published articles, the first-ever preliminary report was by Yoda
and colleagues from Nara Institute of Science and Technology, Japan. In their
pioneer work, they screened a set of defense reaction genes upregulated during the
hypersensitive response (HR) in wild tobacco (Cv. Xanthi nc) upon Tobacco mosaic
virus (TMV) infection using fluorescent differential display (Yoda et al. 2002). The
full-length deduced TIZZ protein contained a single WRKY domain which showed
high similarity to one of the WRKY family members, namely WIZZ. Their results
indicated the presence of a novel type of WRKY protein(s) that might play a critical
role in HR signal activation. The more profound support for the role of WRKY genes
against viral pathogens was given by Liu and group article published in The Plant
Journal (Liu et al. 2004). In their article, they used a candidate gene approach to
identify defense genes that play a role in immunity against TMV. TRV-VIGS based
downregulation of several candidate genes including WRKY1-WRKY3 confirmed the
compromised N-mediated resistance to TMV (Liu et al. 2004). In another study, a
WRKY gene, namely CaWRKY-a from Capsicum annuum (Cv. Bugang) was
isolated (Park et al. 2006). The overexpression of CaWRKY-a in transgenic plants
11 Role of WRKY Transcription Factor Superfamily in Plant Disease Management
341
Small RNAs (smRNA) regulate WRKY TFs under pathogen response by RNA
interference, RNA silencing, or post-transcriptional gene silencing (PTGS) (Voinnet
2009). After several phytohormone treatments in rice, several miRNAs were
induced; out of which, miR167f encoded an NBS-LRR disease resistance protein
(Liu et al. 2009). Double mutants of Atwrky18 Atwrky40 provide resistance to G.
orontii by enhaning the expression of RCD One5 (SRO5) which allows siRNA
production and leads to suppression of WRKY TFs (Borsani et al. 2005). Similarly,
AvrPtoB an effector secreted by P. syringae protein suppresses host miRNAs which
lead to suppression of AtWRKY30 (Navarro et al. 2008). Production of secondary
metabolites can be regulated by miRNA which provides resistance against fungi.
Expression profiling of apple (Cv. Golden Delicious) infected with leaf spot fungus
(A. alternata f. sp. mali.) confirmed that both Md-miR156ab and MdmiR395 target
MdWRKYN1 and MdWRKY26, respectively, and regulate resistance against the
pathogen (Zhang et al. 2017). After the inoculation of F. oxysporum in Persicaria
minor (a herb), the miRNAs get upregulated and downregulated by the WRKY TFs
and terpenoid biosynthesis was reduced (Samad et al. 2019).
11.5 Role of WRKY TFs Against Phytopathogens
11.5.1 Role of Host Plant WRKY Against Viral Diseases
As described earlier, the WRKY TFs are one of the highly studied regulatory protein
family which play both positive and negative role in plant immunity (Chen et al.
2019). One of the major challenges to plant immunity is the onset of viral diseases
(Honjo et al. 2020). There are already many reports in the literature by various
research groups for the bolstering support of the role of WRKY TFs against plant
viruses. Out of all published articles, the first-ever preliminary report was by Yoda
and colleagues from Nara Institute of Science and Technology, Japan. In their
pioneer work, they screened a set of defense reaction genes upregulated during the
hypersensitive response (HR) in wild tobacco (Cv. Xanthi nc) upon Tobacco mosaic
virus (TMV) infection using fluorescent differential display (Yoda et al. 2002). The
full-length deduced TIZZ protein contained a single WRKY domain which showed
high similarity to one of the WRKY family members, namely WIZZ. Their results
indicated the presence of a novel type of WRKY protein(s) that might play a critical
role in HR signal activation. The more profound support for the role of WRKY genes
against viral pathogens was given by Liu and group article published in The Plant
Journal (Liu et al. 2004). In their article, they used a candidate gene approach to
identify defense genes that play a role in immunity against TMV. TRV-VIGS based
downregulation of several candidate genes including WRKY1-WRKY3 confirmed the
compromised N-mediated resistance to TMV (Liu et al. 2004). In another study, a
WRKY gene, namely CaWRKY-a from Capsicum annuum (Cv. Bugang) was
isolated (Park et al. 2006). The overexpression of CaWRKY-a in transgenic plants
11 Role of WRKY Transcription Factor Superfamily in Plant Disease Management
341