Lectin-like glycoprotein PsNLEC-1 is not correctly glycosylated and targeted in boron-deficient pea nodules

Symbiosome development was studied in pea root nodules from plants growing in the absence of boron (B), Rhizobia released into the host cells of nodul es from B-deficient plants developed to abnormal endophytic forms with an a ltered electrophoretic lipopolysaccharide pattern. Immunostaining after sod ium dodecyl sulfate-polyacrylamide gel electrophoresis and electroblotting of nodule homogenates with antibodies that recognize glycoprotein component s showed that two previously described lectin-like glycoproteins (PsNLEC-1A and PsNLEC-1B) did not harbor the carbohydrate epitope normally recognized by specific monoclonal antibodies. Material derived from B-deficient nodul es, however, still contained three antigenic isoforms with similar electrop horetic mobilities to PsNLEC-1 isoforms A, B, and C, These could be detecte d following immunoblotting and immunostaining with a specific antiserum ori ginating from the purified PsNLEC protein that had been heterologously expr essed in Escherichia coli, Immunogold localization of PsNLEC-1 sugar epitop es in B-deficient nodules showed that they were associated mostly with cyto plasmic vesicles rather than normal localization in the symbiosome compartm ent of mature infected cells, These results suggest that a modification of the glycosyl-moieties of PsNLEC-1 and an alteration of vesicle targeting oc cur during the development of pea nodules in the absence of B, and that the se changes are associated with the development of aberrant nonfunctional sy mbiosomes.