DEVELOPMENTAL AND PATHOGEN-INDUCED ACCUMULATION OF TRANSCRIPTS OF POLYGALACTURONASE-INHIBITING PROTEIN IN PHASEOLUS-VULGARIS L

Expression of the polygalacturonase-inhibiting-protein gene (pgip) dur ing development of French bean (Phaseolus vulgaris L. cv. Red Kidney) was analysed in various organs, including leaves, stems and roots of e tiolated and light-grown seedlings, light-grown adult plants, as well as flowers, pods, and seeds. In light-grown seedlings and plants, pgip transcripts were detected in all tissues examined, with higher levels found in the transition zone between the elongating and mature region of young hypocotyls, and in the basal region of the stem of adult pla nts. In etiolated hypocotyls, levels of pgip transcripts in the elonga ting region were five- to six fold higher than in light-grown hypocoty ls. High levels of transcripts were also observed in pods. Accumulatio n of pgip mRNA was also followed in both compatible and incompatible r ace-cultivar interactions between Colletotrichum lindemuthianum races alpha and gamma, respectively, and P. vulgaris is by Northern blot ana lysis and in situ hybridisation. In situ experiments showed, in incomp atible interactions, a rapid, intense and transient accumulation of pg ip mRNA in epidermal cells proximal to the site of infection, and, les s intense, within the cortical parenchyma underneath. In compatible in teractions, no substantial accumulation of pgip mRNA was observed in h ypocotyls; a very weak accumulation was observed in leaves during lesi on formation.