Acetyl-CoA Carboxylase during Development of Plastids in Wild-Type and Mutant Barley Seedlings

Abstract

A soluble acetyl-CoA carboxylase in homogenates of leaves from wild-type barley [Hordeum vulgare] seedlings was studied. Centrifuging the homogenate at 150,000 .times. g did not reduce the total activity, but raised the specific activity. During chloroplast development in light-grown seedlings or during light-dependent greening of leaves grown in the dark, both the total activity of the carboxylase per plant and the specific activity per mg of protein present in homogenates of the seedlings increased rapidly. The soluble leaf acetyl-CoA carboxylase was studied in a number of barley mutants with lesions in chloroplast development. In a group of 3 mutants light elicited an increase in acetyl-CoA carboxylase activity as in the wild-type. In 2 mutants light caused a decrease in activity. Dark-grown leaves of mutant albina-f17 contained levels of soluble acetyl-CoA carboxylase reached only in the light by the wild-type, whereas light-grown albina-f17 seedlings lacked carboxylase activities. The possibility is discussed that leaf cells contain 2 forms of acetyl-CoA carboxylase, 1 soluble with unknown location and a dissociable form located in the chloroplast.