NaJAZh Regulates a Subset of Defense Responses against Herbivores and Spontaneous Leaf Necrosis inNicotiana attenuataPlants    

Abstract

The JASMONATE ZIM DOMAIN (JAZ) proteins function as negative regulators of jasmonic acid signaling in plants. We cloned 12 JAZ genes from native tobacco (Nicotiana attenuata), including nine novel JAZs in tobacco, and examined their expression in plants that had leaves elicited by wounding or simulated herbivory. Most JAZ genes showed strong expression in the elicited leaves, but NaJAZg was mainly expressed in roots. Another novel herbivory-elicited gene, NaJAZh, was analyzed in detail. RNA interference suppression of this gene in inverted-repeat (ir)JAZh plants deregulated a specific branch of jasmonic acid-dependent direct and indirect defenses: irJAZh plants showed greater trypsin protease inhibitor activity, 17-hydroxygeranyllinalool diterpene glycosides accumulation, and emission of volatile organic compounds from leaves. Silencing of NaJAZh also revealed a novel cross talk in JAZ-regulated secondary metabolism, as irJAZh plants had significantly reduced nicotine levels. In addition, irJAZh spontaneously developed leaf necrosis during the transition to flowering. Because the lesions closely correlated with the elevated expression of programmed cell death genes and the accumulations of salicylic acid and hydrogen peroxide in the leaves, we propose a novel role of the NaJAZh protein as a repressor of necrosis and/or programmed cell death during plant development.

Flower-specific jasmonate signaling regulates constitutive floral defenses in wild tobacco

“…1 G and H). One hour after W+R elicitation, JA and JA-Ile levels are known to attain maximum values in leaves (56). Remarkably, the levels of JA-Ile were 6.2-fold higher in floral stage 1 than in herbivore-elicited leaves and remained higher throughout floral development (Fig.…”

“…The expression of JAZ genes is usually rapidly induced in leaves by mechanical wounding or herbivore feeding (56,61). NaJAZi transcripts were dramatically increased 1.5 h after wounding or W+R treatments (SI Appendix, Fig.…”

“…These compounds have all been shown to play important roles in the defense of leaves, and all are induced in leaves by herbivore feeding (51)(52)(53)(54)(55). Here we analyzed (E)-α-bergamotene emission 5 h after wounding and Manduca sexta regurgitant (W+R) treatment and the other compounds and proteins 3 d after W+R treatment in leaves, to detect maximum levels (56). Nontreated leaves at each time point served as controls.…”

Smoking out the masters: transcriptional regulators for nicotine biosynthesis in tobacco

“…Suppression of Nicotiana COI1 effectively impaired JA-and wound-induced nicotine formation along with other JA responses (Paschold et al 2007;Shoji et al 2008). Like their Arabidopsis counterparts, Nicotiana JAZ transcripts and proteins are induced and degraded, respectively, in response to JA (Oh et al 2012;Shoji et al 2008). Expression of truncated forms of JAZs lacking the C-terminal Jas motif, which may act in a dominant-negative manner by forming non-functional JAZ dimers, also clearly inhibited nicotine induction by JA (Shoji et al 2008).…”

“…Expression of truncated forms of JAZs lacking the C-terminal Jas motif, which may act in a dominant-negative manner by forming non-functional JAZ dimers, also clearly inhibited nicotine induction by JA (Shoji et al 2008). Interestingly, RNA interference-mediated knockdown of a single JAZ member in N. attenuata, JAZh, significantly reduces nicotine levels, but enhances other JA-dependent responses (Oh et al 2012). These latter observations, which seem contradictory at first glance, implicate mutual cross-regulation of JAZs, where JAZh may negatively regulate other JAZs that act as repressors of the nicotine response.…”