Organization of microtubules in developing pea root nodule cells

Abstract

Pisum sativum L. (pea) root nodule cells undergo many cellular changes in response to infection by Rhizobium leguminosarum bv. viciae. These include cell 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. The organization of microtubules was examined in developing pea root nodules using fluorescence and electron microscopy techniques. Immunolabelling of microtubules in meristematic cells showed diffuse fluorescence in the cell cortex and adjacent to the nuclear envelope. Recently infected cells contained randomly oriented cortical microtubules and cytoplasmic microtubules that were fragmented with diffuse fluorescence. Infected cells contained an extensive network of long, randomly arranged cortical microtubules with some parallel bundles. Cytoplasmic microtubules in single optical sections of infected cells appeared as short undulating filaments; however, overlapping images from a Z-series of an infected cell showed that the microtubules are long and wavy, and generally radiate inward from the cell cortex.Key words: nodule, microtubules, Rhizobium, pea, symbiosis.

The Cytoskeleton as a Regulator and Target of Biotic Interactions in Plants

“…Cortical microtubules may be responsible for maintaining mitochondria and plastids in the periphery of nodule cells (Timmers et al, 1998;Whitehead et al, 1998;Davidson and Newcomb, 2001b). In alfalfa and pea, radial arrays of microtubules emanating from the cell periphery are likely to orient and position elongated symbiosomes that lie perpendicular to the cell walls (Timmers et al, 1998;Whitehead et al, 1998;Davidson and Newcomb, 2001b).…”

“…In alfalfa and pea, radial arrays of microtubules emanating from the cell periphery are likely to orient and position elongated symbiosomes that lie perpendicular to the cell walls (Timmers et al, 1998;Whitehead et al, 1998;Davidson and Newcomb, 2001b). In pea and soybean, actin microfilaments also occur in the cell cortex, parallel to the microtubules, and both cytoskeletal elements form arrays surrounding the nucleus (Whitehead et al, 1998;Davidson and Newcomb, 2001a).…”

A model for the development of the rhizobial and arbuscular mycorrhizal symbioses in legumes and its use to understand the roles of ethylene in the establishment of these two symbioses

“…1) (Brewin 1998). Recently infected cells undergo reorganization of their microtubules, probably in preparation for the arrival of the microsymbionts (Davidson and Newcomb 2001b); the cells increase in size and their DNA endoreduplicates (Timmers et al 1998). Bacteria, in the droplet, undergo differentiation and become bacteroids (Fig.…”

The role of the plant cytoskeleton in the interaction between legumes and rhizobia

“…This newly formed cytoskeleton consists of MTs radiating perpendicularly from the cell wall of the invaded cells, thus being parallel in alignment to the nitrogen‐fixing bacteroids (Timmers et al, 1998). A similar disorganization is also observed in the nodules of pea (Davidson & Newcomb, 2001b). By contrast, no disorganization was observed in the so‐called ‘empty nodules’ that do not contain differentiating bacteroids, such as those induced by bacterial exoA mutants, elicited by Nod factors or spontaneously developing nodules (nodulation in the absence of rhizobia (NAR) phenotype, Truchet et al, 1989).…”