The Sulfated Laminarin Triggers a Stress Transcriptome before Priming the SA- and ROS-Dependent Defenses during Grapevine's Induced Resistance against Plasmopara viticola

Abstract

Grapevine (Vitis vinifera) is susceptible to many pathogens which cause significant losses to viticulture worldwide. Chemical control is available, but agro-ecological concerns have raised interest in alternative methods, especially in triggering plant immunity by elicitor treatments. The β-glucan laminarin (Lam) and its sulfated derivative (PS3) have been previously demonstrated to induce resistance in grapevine against downy mildew (Plasmopara viticola). However, if Lam elicits classical grapevine defenses such as oxidative burst, pathogenesis-related (PR)-proteins and phytoalexin production, PS3 triggered grapevine resistance via a poorly understood priming phenomenon. The aim of this study was to identify the molecular mechanisms of the PS3-induced resistance. For this purpose we studied i) the signaling events and transcriptome reprogramming triggered by PS3 treatment on uninfected grapevine, ii) grapevine immune responses primed by PS3 during P. viticola infection. Our results showed that i) PS3 was unable to elicit reactive oxygen species (ROS) production, cytosolic Ca2+ concentration variations, mitogen-activated protein kinase (MAPK) activation but triggered a long lasting plasma membrane depolarization in grapevine cells, ii) PS3 and Lam shared a common stress-responsive transcriptome profile that partly overlapped the salicylate- (SA) and jasmonate-(JA)-dependent ones. After P. viticola inoculation, PS3 specifically primed the SA- and ROS-dependent defense pathways leading to grapevine induced resistance against this biotroph. Interestingly pharmacological approaches suggested that the plasma membrane depolarization and the downstream ROS production are key events of the PS3-induced resistance.

Priming of Nicotiana benthamiana antioxidant defences using brown seaweed extracts

“…Fucans enhanced ROS production as well as the accumulation of salicylic acid and antimicrobial compounds in tobacco (Klarzynski et al, 2003). Recently, Gauthier et al (2014) showed that upon inoculation of grapevine with Plasmopara viticola, sulphated laminarins were able to prime ROS-dependent defence pathways leading to enhanced resistance against downy mildew. Thus, we can speculate that the ability of the SE used here to prime for ROS and antioxidant defences is may be due, at least, to their higher content of polysaccharides.…”

Advances in induced resistance by natural compounds: towards new options for woody crop protection

“…Recent studies have shown that ulvan could induce resistance in several plants such as apple against blue mold by Penicillium expansum Link (blue mold) and Botrytis cinerea inducing the activation of CAT and SOD, PAL, POX and polyphenoloxydase (PPO) as well as the levels of lignin and phenolic compounds (Abouraïcha et al, 2015). These studies and others with chemical sulfation of laminarin, suggested that the enhancement of defense responses by algae extracts can be related to its sulfate residue (El Modafar et al, 2012;Gauthier et al, 2014).…”

Surfactin and fengycin contribute to the protection of a Bacillus subtilis strain against grape downy mildew by both direct effect and defence stimulation

“…They were subsequently bleached first with pure methanol at least 2 days and then chloral hydrate solution (1.0 g/L) for 12–24 h until they become completely transparent. Infection sites (corresponding to encysted zoospores) were detected after aniline blue staining (Gauthier et al , ). Four representative fields of each disc and ten discs per condition were observed by epifluorescence microscopy [magnification ×200, λexc = 340–380 nm, λem = 425 nm (long pass filter)].…”