Proline in the Vesicles and Sporelings of Valonia ventricosa and the Concept of Cell Wall Protein

Abstract

THE mature vesicle of Valonia ventricosa was an early source of information about the nature of cellulose¹ and the configuration of a cellulose cell wall^2,3. Later it was used in one of the first investigations with the electron microscope of the way a plant cell wall develops at a naked protoplasmic surface⁴. The opportunity to make such a study was provided by the formation, at will, of aplanospores and by their subsequent development⁵. Aplanospores are small spherical masses of protoplasm, each with a nucleus, and they may form in very large numbers from the multinucleate, non-septate, protoplasm within a single vesicle. This system, therefore, has also provided an opportunity to allow sporelings to develop their cell walls while in contact with ¹⁴C-proline in sea-water. Current methods of autoradiography and electron microscopy make possible determination of the distribution of the radioactivity fixed from ¹⁴C-proline. This should test whether a developing cellulose cell wall incorporates substantial amounts of “cell wall protein” as indicated by radioactivity bound in the form of ¹⁴C-proline. Also the cell wall of mature vesicles of V. ventricosa can easily be obtained free of cytoplasm so that it is possible to ascertain, by direct analysis, how much total protein each contains and its content of proline and/or hydroxyproline.