The Isolation and Characterization on Nongreen Plastids

Most studies of plastids have dealt with green plastids from photosynthetic tissues. This emphasis has been fully deserved considering the roles of chloroplasts in the photosynthetic assimilation of carbon, nitrogen, and sulfur (Jensen 1980), amino acid metabolism (Bryan 1976), fatty acid (Stumpf 1980), terpene (Kreuz and Kleinig 1981) and complex lipid (Mudd and Dezacks 1981) synthesis. Perhaps because of the accumulation of a large body of knowledge derived from these chloroplast studies, there has in recent years been an increasing interest in nongreen, nonphotosynthetic plastids. The recent interest in nongreen plastids is manifold. Etioplasts are thought to represent an intermediate stage in the conversion of proplastids to chloroplasts, and as such have served as a model system for the study of this process. Recent reports on the biochemical nature and role of the prolamellar bodies (Dahlin et al. 1983; Lutz and Nordmann 1983; Ryberg et al. 1983) illustrate the usefulness of the model. Similarly, there has been considerable interest in the roles of nongreen plastids in purine and ureide metabolism in leguminous plants (Boland and Schubert 1983; Shelp et al. 1983), and in fatty acid synthesis and accumulation in developing oilseeds (Dennis and Miernyk 1982). Interest in acetate-derived compounds has led to examination of nongreen plastids in relation to pigment (Camara et al. 1982; Kreuz et al. 1982), terpene (Green et al. 1975), and hydrocarbon (Simcox et al. 1975) synthesis. Finally, studies of nongreen plastids and of the conversion of nongreen to green plastids (Leech and Leese 1982) have contributed to a beginning in the understanding of plastid genesis.