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Abstract

A cDNA of tobacco BY-2 cells corresponding to an mRNA species which was rapidly induced by methyl jasmonate (MeJA) in the presence of cycloheximide (CHX) was found to encode ornithine decarboxylase (ODC). Another cDNA from a MeJA-inducible mRNA encoded S-adenosylmethionine synthase (SAMS). Although these enzymes could be involved in the biosynthesis of polyamines, the level of putrescine, a reaction product of ODC, increased slowly and while the levels of spermidine and spermine did not change following treatment of cells with MeJA. However, N-methylputrescine, which is a precursor of pyrrolidine ring of nicotine, started to increase shortly after MeJA-treatment of cells and the production of nicotine occured thereafter. The levels of mRNA for arginine decarboxylase (ADC), an alternative enzyme for putrescine synthesis, and that for S-adenosylmethionine decarboxylase (SAMDC), required for polyamine synthesis, were not affected by MeJA. In addition to mRNAs for ODC and SAMS, mRNA for putrescine N-methyltransferase (PMT) was also induced by MeJA. Unlike the MeJA-induction of ODC mRNA, MeJA-induction of SAMS and PMT mRNAs were blocked by CHX. The level of ODC mRNA declined after 1 to 4 h following MeJA treatment, while the levels of mRNAs for SAMS and PMT continued to increase. Auxin significantly reduced the MeJA-inducible accumulation of mRNAs for ODC, SAMS and PMT. These results indicate that MeJA sequentially induces expression of a series of genes involved in nicotine biosynthesis by multiple regulatory mechanisms.

A functional genomics approach toward the understanding of secondary metabolism in plant cells

“…2E) and thus demonstrates the coregulation of the pmt gene(s) with the other nicotine metabolic genes. These findings correlate well with earlier reports on the jasmonate inducibility of the genes encoding ornithine decarboxylase and PMT (29).…”

“…The most pronounced secondary metabolites of tobacco are the nicotine alkaloids, which were chosen as reference metabolites. The biosynthesis of nicotine is partially characterized and known to be elicited in BY-2 cells after removal of the growth hormone 2,4-D and the subsequent addition of methyl jasmonate, an oxylipin-type signaling molecule (29). The effects of methyl jasmonate treatment on BY-2 growth and the production of nicotine alkaloids are shown in Fig.…”

Assaying gene content in Arabidopsis

“…There is a second pathway to putrescine in bacteria, plants, and perhaps animal systems (10) involving the conversion of arginine to agmatine by arginine decarboxylase (ADC, EC 4.1.1.19), which subsequently is converted to putrescine. In tobacco these two pathways are differentially regulated (11).…”

Characterization of the spermidine synthase‐related gene family in Arabidopsis thaliana

“…Considering the large body of evidence indicating that the increased resistance to these stresses is associated with the increased amounts of polyamines in plant tissues, SPDS3 might be required for ABA-mediated stress responses. In tobacco cell cultures, genes encoding ADC, ODC and S-adenosylmethionine decarboxylase have been shown to be upregulated by methyl jasmonate (MeJA) [25,26]. We con¢rmed that Table 1 Radioactivities of the HPLC fractions corresponding to putrescine, spermidine and spermine in extracts from yeast spermidine synthase-de¢-cient mutant cells treatment of Arabidopsis seedlings for 2 h with 100 WM of MeJA, salicylic acid, brassinosteroid, or 1-aminocyclopropane-1-carboxylic acid, a precursor of ethylene, causes no alterations in the transcript levels of SPDS1, SPDS2, SPDS3 and ACL5 (data not shown).…”