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

Abstract

Exposure of cell suspension cultures of Medicago truncatula Gaerth. to methyl jasmonate (MeJA) resulted in up to 50-fold induction of transcripts encoding the key triterpene biosynthetic enzyme beta-amyrin synthase (betaAS; EC 5.4.99.-). Transcripts reached maximum levels at 24 h post-elicitation with 0.5 mM MeJA. The entry point enzymes into the phenylpropanoid and flavonoid pathways, L: -phenylalanine ammonia-lyase (PAL; EC 4.3.1.5) and chalcone synthase (CHS; EC 2.3.1.74), respectively, were not induced by MeJA. In contrast, exposure of cells to yeast elicitor (YE) resulted in up to 45- and 14-fold induction of PAL and CHS transcripts, respectively, at only 2 h post-elicitation. betaAS transcripts were weakly induced at 12 h after exposure to YE. Over 30 different triterpene saponins were identified in the cultures, many of which were strongly induced by MeJA, but not by YE. In contrast, cinnamic acids, benzoic acids and isoflavone-derived compounds accumulated following exposure of cultures to YE, but few changes in phenylpropanoid levels were observed in response to MeJA. DNA microarray analysis confirmed the strong differential transcriptional re-programming of the cell cultures for multiple genes in the phenylpropanoid and triterpene pathways in response to MeJA and YE, and indicated different responses of individual members of gene families. This work establishes Medicago cell cultures as an excellent model for future genomics approaches to understand the regulation of legume secondary metabolism.

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

“…Thus, each elicitation time course contained 126 independent culture flasks and biological samples. Cell culture media were also sampled, but at a lower temporal resolution that included 0, 6, 12, 24, and 48 h postelicitation (Suzuki et al, 2005).…”

“…Previous studies used targeted metabolite profiling to demonstrate that MeJA elicits the accumulation of triterpene saponins (Suzuki et al, 2002(Suzuki et al, , 2005Achnine et al, 2005), whereas YE, a pathogen mimic, induces the accumulation of both free and glycosylated isoflavonoids (Kessmann et al, 1990;Suzuki et al, 2005). The changes in primary metabolism in these elicited cell cultures have been described earlier (Broeckling et al, 2005), and a detailed analysis of transcript profiles will appear in a parallel article (Naoumkina et al, 2007).…”

“…Enzymes are as follows: CA4H, cinnamate 4-hydroxylase; CHI, chalcone isomerase; CHR; CHS; CM, chorismate mutase; F2H, flavanone 2-hydroxylase; HI4#OMT, 2,7,4#-trihydroxyisoflavanone 4#-O-methyltransferase; I2#H, isoflavone 2#-hydroxylase; IFS; PAL; PHEA, prephenate deyhdratase. Sato et al, 2007), and the availability of both a custom 16,000 unigene oligonucleotide set (Suzuki et al, 2005) and a 61,200 probe set Affymetrix GeneChip for DNA microarray analyses (http://www.affymetrix.com/ products/arrays/specific/medicago.affx). Unfortunately, the application of such molecular tools to the study of plant secondary metabolism is currently limited by deficient and/or inaccurate annotation of secondary metabolic enzymes and by the incomplete knowledge of the full secondary metabolic composition of plants.…”

Structural Basis for Dual Functionality of Isoflavonoid O-Methyltransferases in the Evolution of Plant Defense Responses

“…truncatula cells were maintained and subcultured in SH medium as previously described (Suzuki et al, 2005). Briefly, 150 mL of 2 mM 6a-hydroxymaackiain dissolved in methanol was added to 15 mL of 5-dold subcultured cells.…”

Volatile terpenoids: multiple functions, biosynthesis, modulation and manipulation by genetic engineering

“…The enhancement in the concentration of terpenes in response to different stresses was usually connected to the increased transcriptional activity of a particular biosynthetic terpene gene (Nagegowda 2010;Nagegowda et al 2010;Xi et al 2012). In Medicago sativa, pathogen attacks cause metabolic and transcriptional changes in the plant cells (Suzuki et al 2005).…”