Immunogold localization of pectin methylesterases in the cortical tissues of flax hypocotyl

Summary Pectin methylesterases (PMEs, EC 3.1.1.11) catalyse the deesterification of pectins. Up to now, most information concerning their location was obtained from biochemical analyses. Taking advantage of specific anti-PME antibodies, we report the precise localization of PMEs at the electron 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 monoclonal antibodies. Our findings show a co-localization of PMEs and acidic pectins (as revealed by JIM5 antibodies) within specific cell wall microdomains. Moreover, PME epitopes are associated with the cellular membranes, particularly with the plasmalemma.Abbreviations Cdta diamino-1,2 cyclohexane tetra-acetic acid - PATAg periodic acid-thiocarbohydrazide-silver proteinate - PME pectin methylesterase - TEM transmission electron microscopy