Overexpression of a heterologoussamgene encoding S‐adenosylmethionine synthetase in flax (Linum usitatissimum) cells: Consequences on methylation of lignin precursors and pectins

Abstract

The Arabidopsis thaliana sam1 gene encoding S-adenosylmethionine synthetase (EC 2.5.1.6) was transferred to flax (Linum usitatissimum) cells via Agrobacterium tumefaciens. This enzyme catalyses the conversion of methionine to S-adenosylmethionine (SAM), the major methyl group donor in living cells. The aim of this work was to study the consequences of an increased SAM-synthetase (SAM-S) activity in transgenic cell lines on both the production of mono- and dimethoxylated lignin monomers and the degree of methylesterification of pectins. Hypocotyls were cocultivated with Agrobacterium tumefaciens strain GV3101 (pGV2260) harbouring the pO35SSAM binary vector carrying the sam1 gene under the control of the 35S promoter and the nptII gene for selection of putative transformed cells. Most of the transgenic cell lines exhibited a significant (up to 3.2-fold) increase in SAM-S activity compared to the controls. The results showed that for the cell lines analysed this transformation had no effect on caffeic acid O-methyltransferase (COMT, EC 2.1.1.68) in vitro activity, degree of methoxylation of lignin precursors or lignin deposition, pectin methyltransferase (PMT, EC 2.1.1) in vitro activity, but led to an increase of pectin methylesterification in friable and fast-growing transgenic cell lines.

Differential accumulation of monolignol-derived compounds in elicited flax (Linum usitatissimum) cell suspension cultures

“…This phenomenon was particularly marked after elicitation with F. oxysporum extracts. The labile ether lignin fraction of both control and elicited flax cells was mainly constituted of G units, as already observed in flax callus cultures (Lamblin et al 2001). However, F. oxysporumtreated cells displayed a dramatic 36-fold increase in S unit content as compared to the control cells.…”

“…The dried extract was dissolved in 1.5 ml of methanol:water (1/1) and filtered (0.45 lm) prior to injection on a Spherisorb (Merck, S5 ODS2 C-18 250·4.6 mm, 5 lm) column. Elution gradient proceeded as previously described (Lamblin et al 2001): A (acetonitrile, orthophosphoric acid 1& in Milli-Q water, 10:90) 100-92% for 6 min; then 92-0% A with solvent B (methanol; orthophosphoric acid 1& in Milli-Q water, 80:20) and C (acetonitrile; orthophosphoric acid 1& in Milli-Q water, 80:20) 0-50% for 29 min. UV detection was performed using water photodiode array detector.…”

Pectin Methyl Esterase Inhibits Intrusive and Symplastic Cell Growth in Developing Wood Cells ofPopulus

“…By generating methyl-free HG stretches, thus creating stiff pectin-calcium-pectin structures and stabilizing pectin network, PttPME1 would strengthen cellular adhesion and hinder intrusive growth. Similar to PttPME1, PME isoforms in flax and tomato had a cell adhesion-promoting role (Lamblin et al, 2001;Orfila et al, 2001;Lacoux et al, 2003). Conversely the appearance of the LM7 epitope (Fig.…”

Cell Wall Polysaccharide Synthesis

“…The question of whether such HG-MTs are preferentially involved in the initial methylation of HG or in the methylation of more highly esterified HG remains to be resolved. The observation that overexpression of an Arabidopsis S-adenosylmethionine (SAM) synthetase gene in flax leads to a concomitant increase in SAM synthetase activity and of pectin methylesterification in the wall, with no increase in HG-MT activity, suggests that the degree of methylesterification of HG may be regulated, at least in part, at the level of substrate (i.e., SAM) concentration (338).…”