Elicitor induced defence responses in medicago sativa

Abstract

Summary• The effects are reported here of an elicitor prepared from liquid cultures of an isolate of Verticillium albo-atrum , which is nonpathogenic to Medicago sativa , on accumulation of H 2 O 2 , medicarpin, deposition of phenolic polymer and phenylalanine ammonialyase (PAL) activity in cultured cells of Medicago sativa L. cv. Kabul (lucerne).• PAL activity and phytoalexins were assayed spectrophotometically and by HPLC, respectively. The scopoletin fluorescence-quenching and thioglycolic acid methods were used to measure H 2 O 2 and phenolic polymer deposition, respectively.• Studies with inhibitors suggested that an NAD(P)H oxidase and a peroxidase were involved in the elicitor stimulated accumulation of H 2 O 2 and that an increase in cytosolic Ca 2+ , but not H 2 O 2 , was part of a signalling pathway leading to the induction of defence responses.• Both the influx of Ca 2+ and release of Ca 2+ from intracellular stores forms part of the signalling pathway leading from perception of elicitor to induction of defence responses. Although H 2 O 2 is not part of the pathway, evidence is presented that O 2 − is part of the signal transduction chain.

Activation of the oxidative burst by yeast elicitor in Catharanthus roseus cells occurs independently of the activation of genes involved in alkaloid biosynthesis

“…Also, application of O ÁÀ 2 , but not of H 2 O 2 , stimulated phytoalexin formation in these cells (Jabs et al, 1997). In Medicago sativa, O ÁÀ 2 has also been implicated as an intermediate signal in the elicitorstimulated production of the phytoalexin medicarpin (Tang and Smith, 2001). In tobacco leaves, ROS were reported to be involved in the induction of transcription of a gene encoding an enzyme of the sesquiterpenoid biosynthetic pathway in response to glycoprotein elicitor (Costet et al, 2002).…”

Methyl jasmonate and yeast elicitor induce differential transcriptional and metabolic re-programming in cell suspension cultures of the model legume Medicago truncatula

“…4c,e). The isoflavonoid phytoalexin conjugate medicarpin glucoside, a compound previously observed to accumulate in elicited cultures of the related species alfalfa (M. sativa; Kessmann et al 1990;Tang and Smith 2001), was identified in the soluble fraction, and p-coumaric acid (both cisand trans-), p-hydroxybenzoic acid and p-hydroxybenzaldehyde were identified in the wall-bound fraction. Essentially identical results were for obtained culture I (data not shown).…”

Metabolomics Reveals Novel Pathways and Differential Mechanistic and Elicitor-Specific Responses in Phenylpropanoid and Isoflavonoid Biosynthesis in Medicago truncatula Cell Cultures

“…In Lupin (Lupinus albus and Lupinus angustifolius) seedlings, YE and fungal infection both induced marked changes in the profiles of isoflavonoid aglycones, but not of glycosidic conjugates (Bednarek et al, 2001(Bednarek et al, , 2003. Medicarpin, a pterocarpan phytoalexin known to accumulate in elicited cell cultures of alfalfa (Tang and Smith, 2001), was induced up to 15-fold in response to YE. Increased levels of the medicarpin precursors formononetin and vestitone were also observed (Fig.…”