salicylates and 2-aminoindan-2-phosphonic-acid

A key tree species for the forest industry in Europe is Norway spruce [Picea abies (L.) Karst.]. One of its major diseases is stem and butt rot caused by Heterobasidion parviporum (Fr.) Niemelä & Korhonen, which causes extensive revenue losses every year. In this study, we investigated the parallel induction of Norway spruce genes presumably associated with salicylic acid- and jasmonic acid/ethylene-mediated signalling pathways previously observed in response to H. parviporum. Relative gene expression levels in bark samples of genes involved in the salicylic acid- and jasmonic acid/ethylene-mediated signalling pathways after wounding and inoculation with either the saprotrophic biocontrol fungus Phlebiopsis gigantea or with H. parviporum were analysed with quantitative PCR at the site of the wound and at two distal locations from the wound/inoculation site to evaluate their roles in the induced defence response to H. parviporum in Norway spruce. Treatment of Norway spruce seedlings with methylsalicylate, methyljasmonate and inhibitors of the jasmonic acid/ethylene signalling pathway, as well as the Phenylalanine ammonia lyase inhibitor 2-aminoindan-2-phosphonic acid were conducted to determine the responsiveness of genes characteristic of the different pathways to different hormonal stimuli. The data suggest that jasmonic acid-mediated signalling plays a central role in the induction of the genes analysed in this study irrespective of their responsiveness to salicylic acid. This may suggest that jasmonic acid-mediated signalling is the prioritized module in the Norway spruce defence signalling network against H. parviporum and that there seems to be no immediate antagonism between the modules in this interaction.

Topics: Basidiomycota; Cyclopentanes; Ethylenes; Gene Expression; Gene Expression Regulation, Plant; Genes, Plant; Host-Pathogen Interactions; Indans; Organophosphonates; Oxylipins; Phenylalanine Ammonia-Lyase; Picea; Plant Bark; Plant Diseases; Salicylates; Signal Transduction

We studied the relationship between biosynthesis of salicylates, the main chemical defenses in willow and growth of Salix pentandra by cultivating plants in the presence of 2-aminoindan-2-phosphonic acid (AIP), a powerful inhibitor of phenylalanine ammonia-lyase (PAL: EC 4.3.1.5.). AIP inhibited efficiently, though not totally, the endogenous synthesis of salicylates. This inhibition markedly increased plant growth. Exogenous application of the precursors of salicylates, benzoic acid (BA), salicylic acid (SA), and helicin, increased the levels of several individual salicylates, but decreased the growth of plants cultivated in the presence of AIP. These results suggest a trade-off between plant growth and the synthesis of salicylates in S. pentandra. Phenylalanine, which accumulated in response to inhibitor treatment, but was decreased by precursor treatments, may be a common and limiting precursor for both plant growth and salicylate synthesis. The biosynthesis of salicin is suggested to proceed mainly via benzoyl-glucose, an intermediate in the synthesis of salicylic acid. Salicin is the most obvious precursor of more substituted salicylates, salicortin, acetylsalicortin, and tremulacin. In addition, we found that the salicylate pools of mature plant parts of S. pentandra were not subject to turnover, implying that the maintenance of salicylates does not demand high resources of plants, although their initial construction is costly.

Topics: Adaptation, Physiological; Animals; Feeding Behavior; Indans; Insecta; Organophosphonates; Phenylalanine; Plants, Edible; Salicylates; Salix