Plastid DNA Levels in Albino and Green Leaves of the «albostrians» Mutant of Hordeum vulgare

Abstract

Summary The levels of plastid DNA (pt DNA) in both the green and albino leaves of the barley mutant «albostrians» (Hordeum vulgare, Mutant 4205) are the same. The albino leaves of this plant are similar in size to green leaves and contain numerous undifferentiated plastid structures. They have previously been shown to contain no plastid ribosomes, (Borner et al., 1976). These plastids contain a single pt DNA nucleoid while fully differentiated chloroplasts in green leaves each contain a number of small, peripherally located nucleoids. We conclude that both the replication of pt DNA and the formation of simple undifferentiated plastids does not require plastid protein synthesis, is controlled by nuclear DNA, and is mediated by the cytoplasmic protein synthesizing system. We suggest that during differentiation pt DNA is redistributed through the plastid matrix. The implications of these observations in relation to the standing of the concept that plastids are semi-autonomous, self-replicating organelles is discussed.