Organization of microtubules in developing pea root nodule cells

Pisum sativum L. (pea) root nodule cells undergo many cellular changes in r esponse to infection by Rhizobium leguminosarum bv. viciae. These include c ell growth, organelle reorganization, and changes relating to the increase in the number of bacteria within the cell. The objective of this study was to characterize microtubule organization during nodule cell development. Th e organization of microtubules was examined in developing pea root nodules using fluorescence and electron microscopy techniques. Immunolabelling of m icrotubules in meristematic cells showed diffuse fluorescence in the cell c ortex and adjacent to the nuclear envelope. Recently infected cells contain ed randomly oriented cortical microtubules and cytoplasmic microtubules tha t were fragmented with diffuse fluorescence. Infected cells contained an ex tensive network of long, randomly arranged cortical microtubules with some parallel bundles. Cytoplasmic microtubules in single optical sections of in fected cells appeared as short undulating filaments; however, overlapping i mages from a Z-series of an infected cell showed that the microtubules are long and wavy, and generally radiate inward from the cell cortex.