, Volume 30, Issue 6, pp 515-521

Transcriptionally active chromosomes (TACs) of barley chloroplasts contain the α-subunit of plastome-encoded RNA polymerase

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Abstract

Transcriptionally active chromosomes (TACs) were isolated from mature chloroplasts of barley, from proplastids enriched in basal segments of barley primary foliage leaves, and from ribosome-deficient plastids of heat-bleached barley leaves. Immunological analysis with a specific antibody raised against the plastid rpoA gene product revealed that chloroplasts contain an immunoreactive protein of 38 kDa in the TAC fraction which appears to be identical to the α-subunit contained in the soluble RNA polymerase (sRNAP) fraction of the same chloroplasts. However, only traces of immunoreactive protein were detected in a TAC preparation derived from ``proplastids''. A positive correlation could be demonstrated between transcriptional activity and the amount of immunoreactive 38-kDa protein by analyzing different TAC fractions eluting at different times during gel filtration of a standard TAC preparation as well as in TAC preparations obtained under various detergent conditions.

Received: 16 May 1996 / 15 August 1996