TRANSCRIPT ANALYSIS OF THE PCBABC GENES ENCODING THE ANTENNA APOPROTEINS IN THE PHOTOSYNTHETIC PROKARYOTE, PROCHLOROTHRIX-HOLLANDICA - ENGLISH, AFRIKAANS

The tightly linked pcbABC genes encode the chlorophyll dib-binding apo proteins in the oxygenic photosynthetic prokaryote Prochlorothrix holl andica. Northern blotting experiments employing gene-specific DNA prob es have identified a complex pattern of transcription from the pcb reg ion. A large 4.4-kb transcript detected in cultures maintained in high light, low light and in darkness results from the cotranscription of all three genes, whereas pcbAB, pcbBC and individual pcbA, B, and C mR NAs are similarly detected in all light regimes. The half lives of the RNAs vary from 15 min for the pcbA BC transcript, to over 60 min for the pc hii and pcbC mRNAs. The lack of identifiable promoter sequences other than the region upstream from pcbA, plus the enhanced stability of the individual single gene transcripts, suggest that the smaller R NA species arise from processing of larger transcripts. Transcription and mRNA turnover occurs largely independent of light intensity, in co ntrast to what is seen in most other phototrophs, in which light influ ences the accumulation of antenna apoprotein gene mRNAs. (C) 1998 Fede ration of European Microbiological Societies. Published by Elsevier Sc ience B.V. All rights reserved.