IMMUNOGOLD LOCALIZATION OF PECTIN METHYLESTERASES IN THE CORTICAL TISSUES OF FLAX HYPOCOTYL

Pectin methylesterases (PMEs, EC 3.1.1.11) catalyse the deesterificati on of pectins. Up to now, most information concerning their location w as obtained from biochemical analyses. Taking advantage of specific an ti-PME antibodies, we report the precise localization of PMEs at the e lectron microscopy level within the different cortical tissues of flax hypocotyl. Quantitative data on the densities of immunolabelling have been collected, using anti-PME antibodies as well as JIM5 and JIM7 mo noclonal antibodies. Our findings show a co-localization of PMEs and a cidic pectins (as revealed by JIM5 antibodies) within specific cell wa ll microdomains. Moreover, PME epitopes are associated with the cellul ar membranes, particularly with the plasmalemma.