title: Different mechanisms for phytoalexin induction by pathogen and wound signals in Medicago truncatula.
abstract: Cell suspensions of the model legume Medicago truncatula accumulated the isoflavonoid phytoalexin medicarpin in response to yeast elicitor or methyl jasmonate (MJ), accompanied by decreased levels of isoflavone glycosides in MJ-treated cells. DNA microarray analysis revealed rapid, massive induction of early (iso)flavonoid pathway gene transcripts in response to yeast elicitor, but not MJ, and differential induction by the two elicitors of sets of genes encoding transcription factors, ABC transporters, and beta-glucosidases. In contrast, both elicitors induced genes encoding enzymes for conversion of the isoflavone formononetin to medicarpin. Four MJ-induced beta-glucosidases were expressed as recombinant enzymes in yeast, and three were active with isoflavone glucosides. The most highly induced beta-glucosidase was nuclear localized and preferred flavones to isoflavones. The results indicate that the genetic and biochemical mechanisms underlying accumulation of medicarpin differ depending on the nature of the stimulus and suggest a role for MJ as a signal for rapid hydrolysis of preformed, conjugated intermediates for antimicrobial biosynthesis during wound responses.
authors.affiliation: Plant Biology Division, Samuel Roberts Noble Foundation, 2510 Sam Noble Parkway, Ardmore, OK 73401, USA.
authors.forename: Marina
authors.initials: M
authors.lastname: Naoumkina
authors.forename: Mohamed A
authors.initials: MA
authors.lastname: Farag
authors.forename: Lloyd W
authors.initials: LW
authors.lastname: Sumner
authors.forename: Yuhong
authors.initials: Y
authors.lastname: Tang
authors.forename: Chang-Jun
authors.initials: CJ
authors.lastname: Liu
authors.forename: Richard A
authors.initials: RA
authors.lastname: Dixon
mesh_terms: D044602:Cellulases / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism; D002851:Chromatography, High Pressure Liquid; D046913:Medicago truncatula / Q000201:enzymology / Q000235:genetics / Q000378:metabolism* / Q000382:microbiology; D008969:Molecular Sequence Data; D020411:Oligonucleotide Array Sequence Analysis; D012333:RNA, Messenger / Q000235:genetics; D012717:Sesquiterpenes; D015398:Signal Transduction; D013729:Terpenes / Q000378:metabolism*; D014158:Transcription, Genetic; D000094162:Phytoalexins
chemical_list: D012333:RNA, Messenger; D012717:Sesquiterpenes; D013729:Terpenes; D044602:Cellulases; D000094162:Phytoalexins