Development in theDatisca-Coriarianodule type

Abstract

This structural study of development of infected cells in the Datisca Baill. - Coriaria Lindsay nodule type explores several unique features of their symbiosis that are similar in both species of plants, providing the following interpretations of infected cell development occurring in the nodule apex. Infection occurs without cytoplasmic bridge formation, causing vegetative hyphae to proliferate in the cell periphery and requiring much higher rates of infection, relative to other actinorhizae, to efficiently colonize the cell. Multiple infections of the cell produce a number of separate bacterial subcolonies within the plant cell and these develop synchronously to form the multilayered structure of the mature infected cell. A radial array of microtubules is probably responsible for positioning the symbiotic vesicles as a hollow sphere near the central vacuole. During development plasma membranes surrounding individual symbiotic vesicles fuse to cause a large-scale merging of symbiotic vesicles into a common matrix in the mature infected cell. During this process the interfacial matrix around both vegetative hyphae and symbiotic vesicles thickens and changes in quality: immunocytochemistry shows the presence of callose. There is a heterogeneity in nuclear number of infected cells, with most mature infected cells containing eight nuclei.Key words: actinorhiza, bacterial differentiation, callose, cytoskeleton, endoplasmic reticulum, infection.