Lipopolysaccharides of Pectobacterium atrosepticum and Pseudomonas corrugata induce different defence response patterns in tobacco, tomato, and potato

International audienceLipopolysaccharides (LIPS), ubiquitous cell surface components of Gram-negative bacteria, are directly implicated in plant/pathogen interactions. However, their perception by the plant, the subsequent signal transduction in both compatible and incompatible interactions, as well as the defence reactions induced in compatible interactions are as yet poorly understood. We focused on biochemical and physiological reactions induced in cell suspensions of three Solanaceae species (tobacco, tomato, and potato) by purified lipopolysaccharides from Pectobacterium atrosepticum (Pa), a pathogen of potato, and Pseudomonas corrugata (Psc), a pathogen of tomato. LPSPa, and LPSPsc caused a significant acidification of potato, tomato, and tobacco extracellular media, whereas laminarin (a linear beta-1,3 oligosaccharide elicitor) induced an alkalinisation in tobacco and tomato, but not in potato cell suspensions. None of the two LIPS induced the formation of active oxygen species in any of the hosts, while laminarin induced H2O2 production in cells of tobacco but not of tomato and potato. In tomato cells, LIPSPa and LPSPsc induced a strong but transitory stimulation of lipoxygenase activity, whereas laminarin induced a stable or slightly increasing LOX activity over the first 24 h of contact. In tobacco, LOX activity was not triggered by either LPS, but significantly increased following treatment with laminarin. In potato, neither LPS nor laminarin induced LOX activity, in contrast with concentrated culture filtrate of Phytophthora infestans (CCF). These results demonstrate that LPS, as well as laminarin, are perceived in different ways by Solanaceae species, and possibly cultivars. They also suggest that defence responses modulated by LPS depend on plant genotypes rather than on the type of interactio

A β-1,3 glucan sulfate induces resistance in grapevine against Plasmopara viticola through priming of défense responses, including HR-like cell death

International audienceSulfated laminarin (PS3) has been shown previously to be an elicitor of plant defense reactions in tobacco and Arabidopsis and to induce protection against tobacco mosaic virus. Here, we have demonstrated the efficiency of PS3 in protecting a susceptible grapevine cultivar (Vitis vinifera cv. Marselan) against downy mildew (Plasmopara viticola) under glasshouse conditions. This induced resistance was associated with potentiated H2O2 production at the infection sites, upregulation of defense-related genes, callose and phenol depositions, and hypersensitive response-like cell death. Interestingly, similar responses were observed following P. viticola inoculation in a tolerant grapevine hybrid cultivar (Solaris). A pharmacological approach led us to conclude that both callose synthesis and jasmonic acid pathway contribute to PS3-induced resistance

Interaction between polygalacturonase-inhibiting protein and jasmonic acid during defense activation in tomato against Botrytis cinerea

Copyright SpringerOligogalacturonic acids (OGAs) generated from in vitro interaction between fungal polygalacturonase (PG) and bean PG-inhibiting protein (PGIP) were shown to activate phytoalexin biosynthesis in soybean. Based on this observation, it was hypothesized that PGIP-dependent generation of OGAs activates plant defence responses in vivo. We tested the hypothesis that PGIP activates jasmonic acid-dependent responses to pathogens. For this purpose, a population of tomato plants segregating for a mutation in the jasmonate receptor CORONATINE INSENSITIVE1 (coi1) and for overexpression of pear PGIP (pPGIP) was challenged with Botrytis cinerea. The coi1 mutant was hypersensitive to B. cinerea, but overexpression of pPGIP in the coi1 mutant background reduced pathogen susceptibility, suggesting that these two genes independently alter defence responses. In addition, pPGIP overexpression suppressed pathogen induction of salicylic acid in the coi1 mutant and activated expression of acidicß-1,3-glucanase independently of the coi1 mutation. However, expression of proteinase inhibitor II (PIN II) in pPGIP overexpressing tomato plants was dependent on COI1. Effects of pPGIP overexpression on defence are therefore complex and only in the case of PIN II pPGIP acts through COI1Peer reviewe