Hydroxyproline-Rich Glycoprotein Transcripts Exhibit Different Spatial Patterns of Accumulation in Compatible and...

The distribution of transcripts encoding hydroxyproline-rich glycoproteins in hypocotyls of Phaseolus vulgaris L. infected with Colletotrichum lindemuthianum was examined by in situ hybridization to tissue sections. The expression of hypersensitive resistance in an incompatible interaction was accompanied by a massive early accumulation of transcripts in the epidermal, cortical, and perivascular parenchymal tissues immediately adjacent to the inoculation site. In a compatible interaction, there was no accumulation of transcripts in the epidermal and cortical tissues even though fungal hyphae ramified throughout these tissues. However, transcripts accumulated at a later stage in the perivascular tissue directly below the site of infection and in tissue several millimeters from the inoculation site. Thus, there is a spatial and tissue-specific counterpart to the differential timing of transcript accumulation in incompatible versus compatible interactions (AM Showalter, JN Bell, CL Cramer, JA Bailey, CJ Lamb [1985] Proc Natl Acad Sci USA 82: 6551-6555). These differences in the spatial distribution and tissue specificity of transcript accumulation imply the differential induction of signaling systems involved in race:cultivar-specific interactions.