Phosphorylation of Plant Plasma Membrane Proteins in Response to Oligosaccharides that Regulate Proteinase Inhibitor Gene Expression

Oligo- and polygalacturonides can signal the induction of the expression of defensive genes in tissues of plants from at least 8 families (Bishop et al 1984; West et al 1984; Darvill and Albersheim 1984). In dicotyledonous plants polygalacturonides are major constituents of the primary cell wall and oligomeric fragments are released in response to pathogen or insect attacks. The nature of the polygalacturonic acid (PGA) oligomers that are released in vivo, and how they interact with target cells to effect gene expression, is poorly understood. Among the chemicals produced in response to oligo- and polygalacturonides are proteins that inhibit the serine class of proteinases (Bishop et al 1981; Ryan 1987). The biochemical basis for signalling processes that regulate the synthesis of proteinase inhibitors in response to insect attacks has been a major focus of this laboratory for several years (Bishop et al 1981; Ryan 1987).