Involvement of nitric oxide in the jasmonate-dependent basal defense against root-knot nematode in tomato plants

Abstract

Jasmonic acid (JA) and nitric oxide (NO) are well-characterized signaling molecules in plant defense responses. However, their roles in plant defense against root-knot nematode (RKN, Meloidogyne incognita) infection are largely unknown. In this study, we found that the transcript levels of the JA- and NO-related biosynthetic and signaling component genes were induced after RKN infection. Application of exogenous JA and sodium nitroprusside (SNP; a NO donor) significantly decreased the number of egg masses in tomato roots after RKN infection and partially alleviated RKN-induced decreases in plant fresh weight and net photosynthetic rate. These molecules also alleviated RKN-induced increases in root electrolyte leakage and membrane peroxidation. Importantly, NO scavenger partially inhibited JA-induced RKN defense. The pharmacological inhibition of JA biosynthesis significantly increased the plants’ susceptibility to RKNs, which was effectively alleviated by SNP application, showing that NO may be involved in the JA-dependent RKN defense pathway. Furthermore, both JA and SNP induced increases in protease inhibitor 2 (PI2) gene expression after RKN infestation. Silencing of PI2 compromised both JA- and SNP-induced RKN defense responses, suggesting that the PI2 gene mediates JA- and NO-induced defense against RKNs. This work will be important for deepening the understanding of the mechanisms involved in basal defense against RKN attack in plants.

Mitigation of sodium chloride toxicity inSolanum lycopersicumL. by supplementation of jasmonic acid and nitric oxide

“…Both JA and NO have been reported to mediate proper plant growth under normal as well as stressful conditions, in addition to playing a unique role in signaling under stress (Zhou et al 2015;Ahmad, Abdel Latef, et al 2016;Ahmad, Rasool, et al 2016). In the present study, S. lycopersicum plants subjected to salinity showed a reduction in the growth parameters; such reduction in morphological parameters might have been due to the NaCl-induced inhibition of cell division and cell elongation (Yasseen et al 1987).…”

“…Of them, jasmonic acid (JA) and nitric oxide (NO) have been shown to be involved in the regulation of several metabolic pathways, under both normal and stressful conditions (Ahmad, Abdel Latef, et al 2016;Ahmad, Rasool, et al 2016;Sirhindi et al 2016Sirhindi et al , 2017Ahmad et al 2017;Bali et al 2017). In addition to their individual effects, it has been proposed that there is a crosstalk among them, for eliciting important growth responses via mediation of signaling events (Zhou et al 2015;Ahmad, Rasool, et al 2016). JA is an important cellular regulator playing an active role in maintaining developmental events, including germination, root growth, leaf movement, embryo development, sex determination, fruit ripening, and senescence (Dar et al 2015;Ahmad, Rasool, et al 2016).…”

Redox and the circadian clock in plant immunity: A balancing act

“…The lack of ROS production by apoplastic peroxidases in A. thaliana renders the plants more susceptible to B. cinerea [45], while addition of NO donors induces JA-mediated defense against root knot nematodes in tomato [59]. NO is also produced in response to wounding [60].…”

“…This complexity allows the plant to select the appropriate defense strategy based on the source of ROS/RNS, preventing conflicting immune responses such as concurrent defense against herbivores and biotrophic pathogens. Furthermore, because ROS/RNS are required for defense against both biotrophs [27,42,48,50] and necrotrophs/herbivores [45,59], they could also play a significant role in limiting the SA-JA antagonism, which is often exploited by attackers [69,70]. For example, the cat2 mutation increases defense against biotrophs but decreases resistance to necrotrophs by suppressing JA biosynthesis [76].…”

Entomopathogenic and plant pathogenic nematodes as opposing forces in agriculture

“…JA biosynthesis and signaling component genes have been found to be upregulated after RKN infection, and exogenous application of JA has been found to reduce root egg masses in tomato plants (Zhou et al, 2015). Exogenous application of the SA analog benzothiadiazole (BTH) to tomato plants also led to a decrease in gall formation, which is believed to be the result of cell-wall stiffening due to increased H 2 O 2 production, lignin accumulation, and peroxidase activity in response to the BTH exposure (Melillo et al, 2014).…”