Oxidative defence reactions in sunflower roots induced by methyl-jasmonate and methyl-salicylate and their relation with calcium signalling

Abstract

Ca(2+) plays a critical role as second messenger in the signal-response coupling of plant defence responses, and methyl-jasmonate and methyl-salicylate are important components of signal transduction cascades activating plant defences. When intact axenic non-induced seedling roots of sunflower were treated with different Ca(2+) concentrations up to 1 mM, there was no significant increase in O(2)(*-) generation or DMAB-MBTH peroxidase (extracellular, ECPOX) activities in the apoplast, probably because these roots had enough Ca(2+) in their exo- and endocellular reservoirs. Both activities were strongly inhibited by the RBOH-NADPH oxidase inhibitor DPI and by the Ca(2+) surrogate antagonist La(3+), but the voltage-dependent Ca(2+) channel blocker verapamil was only inhibitory at concentrations higher than those active on animal L-type Ca(2+) channels. Concentrations >5 mM EGTA (chelating Ca(2+) in the apoplast) and Li(+) (inhibiting PI cycle dependent endogenous Ca(2+) fluxes) also inhibited both activities. W7, inhibitor of binding of Ca-CaM to its target protein, enhanced both activities, but the inactive analogue W5 showed a similar effect. Our data suggest that Ca(2+) from exocellular and, to a lesser extent, from endocellular stores is involved in oxidative activities, and that RBOH-NADPH oxidase is the main system supporting them. Ca(2+) activation of the PM cytosolic side of RBOH-NADPH oxidase is probably the key to Ca(2+) involvement in these processes. Roots induced by MeJA or MeSA showed significant enhancement of both oxidative activities, as corresponding to the oxidative burst evoked by the two phytohormones in the root apoplast. But while ECPOX activity showed a response to the effectors similar to that described above for non-induced roots, O(2)(*-) generation activity in the apoplast of induced roots was insensitive to EGTA, verapamil and Li(+), the inhibitors of exogenous and endogenous Ca(2+) fluxes; only DPI and La(3+) were inhibitory. As exogenously added 0.1 mM Ca(2+) also increased O (2) (.-) generation, we propose that, in these roots, activation of RBOH-NADPH oxidase by Ca(2+) could be regulated by Ca(2+) sensors in the apoplast.

Visual, vibratory, and olfactory cues affect interactions between the red spider mite Tetranychus evansi and its predator Phytoseiulus longipes

“…Both are key compounds in the shikimic acid pathway and are involved in the induction of direct and indirect plant defenses (Dicke and Hilker 2003). A previous study suggested that as part of plant defense response, MeSA induces an oxidative burst in sunflower seedling roots (Garrido et al 2009) and is produced by various plants in response to herbivore damage (Van Den Boom et al 2004;Gadino et al 2012) and also attracts natural enemies of mites including P. persimilis, Aphis glycines (Matsumura) (Dicke et al 1990;Mallinger et al 2011), Chrysopa nigricornis (Burmeister), Hemerobius sp. (Linnaeus), Deraeocoris brevis (Akbulatova), Stethorus punctum picipes (Casey), and Orius tristicolor (White) (James and Price 2004).…”

The effect of methyl salicylate on the induction of direct and indirect plant defense mechanisms in poplar (Populus×euramericana‘Nanlin 895’)

“…MeSA and SA are key compounds in the shikimic acid pathway and are involved in the induction of direct and indirect plant defenses (Dicke & Hilker 2003). MeSA is an important component of the signal transduction cascades, which activate the plant defense response, and it induces an oxidative burst in sunflower seedling roots (Garrido et al 2009).…”

Reactive oxygen species: Reactions and detection from photosynthetic tissues

“…Epinephrine (also called adrenaline) has been used to detect O 2 • as after the reaction with O 2 • , the absorbance of the reaction product, adrenochrome, can be measured (at about 490 nm; [319]). Epinephrine has been used to measure O 2 • from chestnut seeds [320] and spinach chloroplasts [313], extracellular O 2 • production from bryophytes and lichens [281] and roots [191], and mitochondrial O 2 • production from barley roots [321]. This method is not specific to O 2 • , as epinephrine has been shown to react also with H 2 O 2 [322], and therefore specificity assays are always needed (see e.g.…”

“…The effects of ubiquitous plant metabolites on the MBTH-DMAB signal call for special care to assure that the signal actually reflects the H 2 O 2 content of the study material. The MBTH/DMAB method has been used to measure the increase in extracellular peroxidase activity in sunflower roots during defense signaling [191].…”