Overexpression of a heterologous sam gene encoding S-adenosylmethionine synthetase in flax (Linum usitatissimum) cells: Consequences on methylation of lignin precursors and pectins

The Arabidopsis thaliana sam1 gene encoding S-adenosylmethionine synthetase (EC 2.5.1.6) was transferred to flax (Linum usitatissimum) cells via Agrob acterium tumefaciens, This enzyme catalyses the conversion of methionine to S-adenosylmethionine (SARI), the major methyl group donor in living cells, The aim of this work was to study the consequences of an increased SAM-syn thetase (SAM-S) activity in transgenic cell lines on both the production of mono- and dimethoxylated lignin monomers and the degree of methylesterific ation of pectins, Hypocotyls were cocultivated with Agrobacterium tumefacie ns strain GV3101 (pGV2260) harbouring the pO35SSAM binary vector carrying t he sam1 gene under the control of the 35S promoter and the nptII gene for s election of putative transformed cells, Most of the transgenic cell lines e xhibited 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 o r lignin deposition, pectin methyltransferase (PMT, EC 2.1.1) in vitro acti vity, but led to an increase of pectin methylesterification in friable and fast-growing transgenic cell lines.