cross-linking of polymers (Torres et al. 2006). However, the virulent strains of rice
blast can suppress the ROS generated by rice cells by the secretion AvrPii and
AvrPiz-t effectors (Kou et al. 2019). Moreover, virulent strains of M. oryzae utilize
the activity of a variety of proteins including thioredoxin 2, glutathione peroxidase,
glutathione reductase, and nitronate monooxygenases, among others, for the successful detoxification of rice generated ROS to facilitate the infection (Kou et al.
2019).
12.3.4 Production of Antimicrobial Compounds and Phytohormones
It has long been observed that pathogen infection or treatment of chitin results in an
accumulation of antimicrobial compounds in plants, commonly referred to as
phytoalexins. In monocots including rice, these phytoalexins include various
terpenoids, and phenolic compounds, such as phenylamides (Schmelz et al. 2014).
In particular, the accumulation of two phytoalexins, sakuranetin, and momilactone A
was measured in M. oryzae-infected leaves using HPLC–MS/MS. Among them, the
accumulation of Momilactone A was found to be higher in incompatible fungalinfected leaves compared to compatible ones, and Sakuranetin was specifically
accumulated in incompatible fungal-infected samples (Wang et al. 2014).
SA (salicylic acid), JA (jasmonate acid), and ET (ethylene) are three major
phytohormones that play important roles in plant immunity. In dicots, it has been
well established that SA regulates immunity against biotrophic pathogens while JA
regulates growth development and stress responses, especially defense responses to
herbivores and necrotrophic pathogens (Browse 2009). However, there is no such
distinction in the case of monocots including rice (Meng et al. 2019b). SA
measurements in response to M. oryzae inoculation showed no significant change
in SA concentrations before and after inoculation (Silverman et al. 1995). However,
rice plants indeed respond to exogenous SA treatment, indicating that the involvement of SA in rice defense responses is more dependent on the SA signaling, rather
than the endogenous SA level (Silverman et al. 1995). In the case of JA signaling, it
has been observed that JA is involved in rice basal defense against bacterial and
fungal pathogens (Tamaoki et al. 2013; Yamada et al. 2012). JA together with ABA
positively regulate MSP1 induced cell death, while overexpression of MSP1 in rice
confers broad-spectrum resistance through modulation of the SA- and JA-mediated
signaling pathways (Wang et al. 2016). MoHrip1 activates both the SA signaling
pathway and the gibberellin (GA) pathway and suppresses JA signaling (Hong et al.
2017). In the case of ET, multiple reports have been published suggesting that ET
confers broad-spectrum resistance, especially against the fungal infections (Gupta
et al. 2018b).
12 Unraveling the Molecular Mechanism of Magnaporthe oryzae Induced. . .
371
blast can suppress the ROS generated by rice cells by the secretion AvrPii and
AvrPiz-t effectors (Kou et al. 2019). Moreover, virulent strains of M. oryzae utilize
the activity of a variety of proteins including thioredoxin 2, glutathione peroxidase,
glutathione reductase, and nitronate monooxygenases, among others, for the successful detoxification of rice generated ROS to facilitate the infection (Kou et al.
2019).
12.3.4 Production of Antimicrobial Compounds and Phytohormones
It has long been observed that pathogen infection or treatment of chitin results in an
accumulation of antimicrobial compounds in plants, commonly referred to as
phytoalexins. In monocots including rice, these phytoalexins include various
terpenoids, and phenolic compounds, such as phenylamides (Schmelz et al. 2014).
In particular, the accumulation of two phytoalexins, sakuranetin, and momilactone A
was measured in M. oryzae-infected leaves using HPLC–MS/MS. Among them, the
accumulation of Momilactone A was found to be higher in incompatible fungalinfected leaves compared to compatible ones, and Sakuranetin was specifically
accumulated in incompatible fungal-infected samples (Wang et al. 2014).
SA (salicylic acid), JA (jasmonate acid), and ET (ethylene) are three major
phytohormones that play important roles in plant immunity. In dicots, it has been
well established that SA regulates immunity against biotrophic pathogens while JA
regulates growth development and stress responses, especially defense responses to
herbivores and necrotrophic pathogens (Browse 2009). However, there is no such
distinction in the case of monocots including rice (Meng et al. 2019b). SA
measurements in response to M. oryzae inoculation showed no significant change
in SA concentrations before and after inoculation (Silverman et al. 1995). However,
rice plants indeed respond to exogenous SA treatment, indicating that the involvement of SA in rice defense responses is more dependent on the SA signaling, rather
than the endogenous SA level (Silverman et al. 1995). In the case of JA signaling, it
has been observed that JA is involved in rice basal defense against bacterial and
fungal pathogens (Tamaoki et al. 2013; Yamada et al. 2012). JA together with ABA
positively regulate MSP1 induced cell death, while overexpression of MSP1 in rice
confers broad-spectrum resistance through modulation of the SA- and JA-mediated
signaling pathways (Wang et al. 2016). MoHrip1 activates both the SA signaling
pathway and the gibberellin (GA) pathway and suppresses JA signaling (Hong et al.
2017). In the case of ET, multiple reports have been published suggesting that ET
confers broad-spectrum resistance, especially against the fungal infections (Gupta
et al. 2018b).
12 Unraveling the Molecular Mechanism of Magnaporthe oryzae Induced. . .
371