Effect of pectin methylesterase gene expression on pea root development

Expression of an inducible gene with sequences common to genes encoding pec tin methylesterase (PME) was found to be tightly correlated, both spatially and temporally, with border cell separation in pea root caps. Partial inhi bition of the gene's expression by antisense mRNA in transgenic pea hairy r oots prevented the normal separation of root border cells from the root tip into the external environment. This phenotype was correlated with an incre ase in extracellular pH, reduced root elongation, and altered cellular morp hology. The translation product of the gene exhibited PME activity in vitro . These results are consistent with the long-standing hypothesis that the d emethylation of pectin by PME plays a key role in cell wall metabolism.