Integrating nitric oxide into salicylic acid and jasmonic acid/ ethylene plant defense pathways

Abstract

Plant defense against pests and pathogens is known to be conferred by either salicylic acid (SA) or jasmonic acid (JA)/ethylene (ET) pathways, depending on infection or herbivore-grazing strategy. It is well attested that SA and JA/ET pathways are mutually antagonistic allowing defense responses to be tailored to particular biotic stresses. Nitric oxide (NO) has emerged as a major signal influencing resistance mediated by both signaling pathways but no attempt has been made to integrate NO into established SA/JA/ET interactions. NO has been shown to act as an inducer or suppressor of signaling along each pathway. NO will initiate SA biosynthesis and nitrosylate key cysteines on TGA-class transcription factors to aid in the initiation of SA-dependent gene expression. Against this, S-nitrosylation of NONEXPRESSOR OF PATHOGENESIS-RELATED PROTEINS1 (NPR1) will promote the NPR1 oligomerization within the cytoplasm to reduce TGA activation. In JA biosynthesis, NO will initiate the expression of JA biosynthetic enzymes, presumably to over-come any antagonistic effects of SA on JA-mediated transcription. NO will also initiate the expression of ET biosynthetic genes but a suppressive role is also observed in the S-nitrosylation and inhibition of S-adenosylmethionine transferases which provides methyl groups for ET production. Based on these data a model for NO action is proposed but we have also highlighted the need to understand when and how inductive and suppressive steps are used.

Nitrate Increased Cucumber Tolerance to Fusarium Wilt by Regulating Fungal Toxin Production and Distribution

“…The results showed that FA mainly accumulated in the roots of the NO 3 − -fed plants and was increased with a NO 3 − supply (Table 2), which might contribute to the increased tolerance of NO 3 − -fed plants to the toxin, thus limiting FA transport to the ground and reducing damage to the leaf. Moreover, the speculation that the high-NO 3 − -fed plants were more tolerant to FA might be attributed to the increase in the level of defense-associated NO, a signaling molecule that is involved in the kinetics of hypersensitive response (HR) formation [59] and aids the initiation of the SA-dependent gene expression [60]. Additionally, the high-NH 4 + -fed plants that were more susceptible to FA may result from decreased polyamine levels, which are known to increase plant resistance by producing hydrogen peroxide (H 2 O 2 ) [52].…”

Moving nitrogen to the centre of plant defence against pathogens

“…In terms of both NO production elicited via PTI and ETI, one of the most important downstream effects is the initiation of SA biosynthesis (Durner et al, 1998). SA plays a central role in both localized and systemic resistance to infection, and NO is now known to be an integral component of the signalling pathway (Mur et al, 2013). Extensive bioinformatic analysis of NO-responsive promoters in arabidopsis in response to infection found that cis-elements linked to SA responsiveness were prominent (Palmieri et al, 2008).…”

“…Extensive bioinformatic analysis of NO-responsive promoters in arabidopsis in response to infection found that cis-elements linked to SA responsiveness were prominent (Palmieri et al, 2008). Further, NO is known to nitrosylate key cysteines on TGA-class transcription factors to aid in the initiation of SA-dependent gene expression (Lindermayr and Durner, 2009;Lindermayr et al, 2010;Gupta, 2011;Mur et al, 2013;Yu et al, 2014). This can be countered through nitrosylation of A NONEXPRESSOR OF PATHOGENESIS-RELATED PROTEIN1 (NPR1) leading to oligomerization of NPR1 within the cytoplasm to reduce TGA activation (Tada et al, 2008;Lindermayr et al, 2010).…”

Stage-specific reprogramming of gene expression characterizes Lr48-mediated adult plant leaf rust resistance in wheat

“…Following pathogen challenge, and depending on the R gene involved, resistant plants respond rapidly through production of novel transcripts belonging to various pathways involved in metabolism and defense (Torres et al 2003;Bolton et al 2008;Giraud et al 2012). The defense responses, in turn, are also associated with a complex network of downstream signaling pathways that involve the following three signaling molecules: salicylic acid, jasmonic acid, and ethylene (Dong 1998;Thomma et al 2001;Kunkel and Brooks 2002;Nandi et al 2003;Hua 2009;Giraud et al 2012;Mur et al 2013; Van der Does et al 2013). It is also known that the abundance of new transcripts and deployment time of signaling pathways are stress-dependent (Torres et al 2003).…”