Changes in plastid envelope polypeptides during chloroplast development.

A quantitative estimation of sodium dodecyl sulphate-extractable plastid envelope polypeptides during greening of Avena sativa L. laminae is described, combined with protein distribution and plastid number studies over the same period.A primary light-dependent and cytoplasm-dependent increase in both total plastid protein and envelope associated protein during the first 30 minutes of greening was observed, followed by a period during which release of envelope-associated protein either into the plastid or into the cytoplasm, or both, takes place. After 8 hours greening an increase in plastid envelope protein reflects a requirement for an increased plastid surface area during chloroplast maturation.A comparison of the behaviour of envelope membranes during illuminated in vitro incubation of isolated etio-plasts with plastids isolated from tissue given similar illumination pre-treatments, indicates that the early increase in envelope-associated protein is real and requires the participation of the cytoplasm.