2009; Van der Ent et al. 2009b). These TFs are implicated in the regulation of JAand ET-dependent defenses (Fig. 10.3). Further, an in-silico analysis of the promoter
sequences of JA-responsive Arabidopsis genes with expression pattern in
ISR-expressing plants has revealed the presence of a cis-acting G-box-like motif
within the promoters of the ISR-primed genes, which functions as a binding site for
an essential transcriptional regulator, MYC2, of JA-dependent defenses (Pozo et al.
2008). The ISR has been observed to be induced in Arabidopsis, by Bacillus
amyloliquefaciens IN 937a (against Erwinia carotovora), Bacillus pumilus SE34
and Bacillus pumilus (against Pseudomonas syringae pv. maculicola), Pseudomonas fluorescens 89B61 and Serratia marcescens 90–166 T4 (against Pseudomonas
syringae pv. maculicola and Pseudomonas syringae pv. tomato), B. subtilis GB03
(against Erwinia carotovora), Pseudomonas fluorescens CHA0 (against
Peronospora parasitica), and Pseudomonas fluorescens WCS417 (against Pseudomonas syringae pv. tomato) (Iavicoli et al. 2003; Ryu et al. 2003). Whereas, in
tobacco, ISR has been observed to be induced by Bacillus pumilus SE34 (against
Peronospora tabacina) and Pseudomonas chlororaphis 06 and Serratia marcescens
90–166 (against Pseudomonas syrigae pv. tabaci) (Press et al. 1997; Zhang et al.
2002; Spencer et al. 2003). In tomato, ISR has been observed to be induced by
Pseudomonas aeruginosa 7NSK2 and Pseudomonas fluorescens CHA0 (against
Meloidogyne javanica) and Pseudomonas fluorescens 89B61 (against Phytophthora
infestans) (Yan et al. 2002; Siddiqui and Saukat 2004). Furthermore, the
rhizobacterial strains can do differential ISR for variety of plant species or even
for narrow range of plants in a species-specific manner. For instance, Pseudomonas
fluorescens WCS 417 promotes ISR in Arabidopsis, bean, tomato, carnation, and
radish, and Pseudomonas putida WCS 358 promotes ISR in Arabidopsis, bean and
tomato, while Pseudomonas fluorescens WCS 374 is known to cause ISR in only
radish (Gómez-Gómez 2004).
Though many rhizobacteria produce SA, it is frequently not considered as the
causative factor of the perceived systemic resistance (Pieterse et al. 1996; Ran et al.
2005; Djavaheri et al. 2012). However, certain PGPR (Pseudomonas aeruginosa
7NSK2, Paenibacillus alvei K165, Pseudomonas fluorescens SS101) and PGPF
(Trichoderma) are known to prompt an SA-dependent type of ISR resembling the
pathogen induced SAR (Tjamos et al. 2005; Mathys et al. 2012). In most of these,
ROS accumulate as an important elicitor at the site of tissue colonization.
10.7 Herbivore-Induced Resistance (HIR) Signaling
The initiation of HIR signaling at the site of tissue injury occurs after the release of
various HAMPs, plant-derived signals (e.g., DAMPs), and elicitors in insect oral
secretions, which are recognized by PRRs for PTI (Wu and Baldwin 2010; Heil et al.
2012). It is schematically represented in Fig. 10.4. Production of insecticidal toxins
and other feeding deterrents constitute a direct defense of plants against herbivory.
Besides, plants have an indirect defense system against herbivory involving production of volatile compounds that entice natural predators of the attacking herbivores
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sequences of JA-responsive Arabidopsis genes with expression pattern in
ISR-expressing plants has revealed the presence of a cis-acting G-box-like motif
within the promoters of the ISR-primed genes, which functions as a binding site for
an essential transcriptional regulator, MYC2, of JA-dependent defenses (Pozo et al.
2008). The ISR has been observed to be induced in Arabidopsis, by Bacillus
amyloliquefaciens IN 937a (against Erwinia carotovora), Bacillus pumilus SE34
and Bacillus pumilus (against Pseudomonas syringae pv. maculicola), Pseudomonas fluorescens 89B61 and Serratia marcescens 90–166 T4 (against Pseudomonas
syringae pv. maculicola and Pseudomonas syringae pv. tomato), B. subtilis GB03
(against Erwinia carotovora), Pseudomonas fluorescens CHA0 (against
Peronospora parasitica), and Pseudomonas fluorescens WCS417 (against Pseudomonas syringae pv. tomato) (Iavicoli et al. 2003; Ryu et al. 2003). Whereas, in
tobacco, ISR has been observed to be induced by Bacillus pumilus SE34 (against
Peronospora tabacina) and Pseudomonas chlororaphis 06 and Serratia marcescens
90–166 (against Pseudomonas syrigae pv. tabaci) (Press et al. 1997; Zhang et al.
2002; Spencer et al. 2003). In tomato, ISR has been observed to be induced by
Pseudomonas aeruginosa 7NSK2 and Pseudomonas fluorescens CHA0 (against
Meloidogyne javanica) and Pseudomonas fluorescens 89B61 (against Phytophthora
infestans) (Yan et al. 2002; Siddiqui and Saukat 2004). Furthermore, the
rhizobacterial strains can do differential ISR for variety of plant species or even
for narrow range of plants in a species-specific manner. For instance, Pseudomonas
fluorescens WCS 417 promotes ISR in Arabidopsis, bean, tomato, carnation, and
radish, and Pseudomonas putida WCS 358 promotes ISR in Arabidopsis, bean and
tomato, while Pseudomonas fluorescens WCS 374 is known to cause ISR in only
radish (Gómez-Gómez 2004).
Though many rhizobacteria produce SA, it is frequently not considered as the
causative factor of the perceived systemic resistance (Pieterse et al. 1996; Ran et al.
2005; Djavaheri et al. 2012). However, certain PGPR (Pseudomonas aeruginosa
7NSK2, Paenibacillus alvei K165, Pseudomonas fluorescens SS101) and PGPF
(Trichoderma) are known to prompt an SA-dependent type of ISR resembling the
pathogen induced SAR (Tjamos et al. 2005; Mathys et al. 2012). In most of these,
ROS accumulate as an important elicitor at the site of tissue colonization.
10.7 Herbivore-Induced Resistance (HIR) Signaling
The initiation of HIR signaling at the site of tissue injury occurs after the release of
various HAMPs, plant-derived signals (e.g., DAMPs), and elicitors in insect oral
secretions, which are recognized by PRRs for PTI (Wu and Baldwin 2010; Heil et al.
2012). It is schematically represented in Fig. 10.4. Production of insecticidal toxins
and other feeding deterrents constitute a direct defense of plants against herbivory.
Besides, plants have an indirect defense system against herbivory involving production of volatile compounds that entice natural predators of the attacking herbivores
310
L. Thomas and I. Singh