Expression of Extracellular Glycoproteins in the Uninfected Cells of Developing Pea Nodule Tissue. A. L. Rae. John Innes Institute, John Innes Centre, Colney Lane, Norwich NR4 7UH, UK.. S. Perotto, J. P. Knox, E. L. Kannenberg, and N. J. Brewin. John Innes Institute, John Innes Centre, Colney Lane, Norwich NR4 7UH, UK.. MPMI 4:563-570. Accepted 25 July 1991. This article is in the public domain and not copyrightable. It may be freely reprinted with customary crediting of the source. The American Phytopathological Society, 1991.

Two monoclonal antibodies, AFRCMAC265 and JIM13, with specificity for plant extracellular glycoproteins were used to study the organization and development of the uninfected tissue layers in nodules induced on the roots of Pisum sativum by Rhizobium leguminosarum bv. viciae. A 95-kD glycoprotein, recognized by MAC265 and previously identified in the matrix of infection threads, was detected in the intercellular spaces of the uninfected nodule parenchyma and also in the uninfected tissue in the vicinity of the apical meristem. It was also found in the intercellular spaces of empty nodulelike structures induced by a mutant of R. leguminosarum that has a defective lipopolysaccharide structure. Enhanced secretion of this glycoprotein is thus a very early response to Rhizobium infection. A different class of glycoprotein, recognized by JIM13, was localized specifically to cell walls in the endodermal sheath of pea nodules. JIM13 identified differentiating endodermal cells before wall thickening was apparent, and also labeled cytoplasmic vesicles in postmeristematic uninfected cells. JIM13 also identified the incipient endodermis in empty nodulelike structures. We conclude that the expression and secretion of glycoproteins is related to the early differentiation of distinct cell types in the uninfected tissues of the nodule.