Abstract
Pectin methylesterases (PMEs) are a class of enzymes capable of catalyzing the demethylesterification of cell wall pectins. Although PMEs are implicated in regulating mechanical properties of the cell wall, functions of individual members are not clear. Our comprehensive analyses on cell-wall related genes in Arabidopsis thaliana have identified a PME, which is expressed specifically in certain cell files within cortical cells in basal part of stems. A null mutant for this gene, pme61, carries thinner and more fragile stems compared to wild type plants. The mutant exhibits aberrant cell-wall morphology in the specific cell files. We also have revealed that degree of metylesterification is higher and that the PME activity is lower in pme61 than in that of wild type. Thus, we conclude that AtPME61 works as a primary PME in the basal part of stem, and plays an essential role for formation of supporting tissues.
