Antisense transgenesis of Linum usitatissimum with a pectin methylesterase cDNA

A cDNA of a flax (Linum usitatissimum) pectin methylesterase (PME) gene, Lupme3, was isolated by RACE-PCR. A partial sequence of this cDNA was inserted in antisense orientation downstream the cauliflower mosaic virus 35S promoter and introduced into the flax genome via Agrobacterium tumefaciens. Transgenic calli derived from the cocultivated explants were analysed for the antisense sequence expression, and for their PME activity as well as their degree of pectin methylesterification and level of bound cations in the cell wall. Expression of the antisense sequence was correlated with a decrease of sense transcripts and a decrease of the PME enzyme activity of cell extracts at pH 8.5. In transgenic cells, a slight increase of activity was observed at acidic pH (5.5), possibly due to a compensation phenomenon and a moderately basic isoform appeared on IEF of transgenic lines. A decrease of the bound potassium level was also noted.