Résumé
Pectin demethylesterification appears to be catalysed by a number of pectin methylesterase (PME) isoenzymes in higher plant species. In order to better define the biological role of these isoenzymes in plant cell growth and differentiation, we undertook molecular studies on the
PME-encoding genes in
Arabidopsis thaliana. In this paper, we report the characterization of
AtPME3, a new
PME-related gene of 4
kb in length that we have mapped on Chromosome III.
AtPME3 encodes a putative mature PME-related isoenzyme of 34
kDa with a basic isoelectric point. Since the extent of the gene family encoding PME in higher plant species is still unknown, we resorted to the use of degenerate primers designed from several well-known consensus regions to identify new
PME-related genes in the genome of
Arabidopsis. Our results, in combination with several known expressed sequences tags (
ESTs), indicate that the
Arabidopsis genome contains at least 12
PME-related genes. Consequently, a method of systematic gene expression analysis has been applied in order to discern the expression pattern of these 12 genes throughout the plant at the floral stage. Whereas most of these genes appeared to be more or less ubiquitously expressed throughout the plant, several genes are distinguishable by their strikingly specific expression in certain organs. The present data bring a new insight into the role of specific
PME-related genes in flower and root development.