Rps10 and 6 other Ribosomal Protein Genes from the S10/Spc-Operon not Encountered On Higher Plant Plastid DNA ARE Located on the Cyanelle Genome of Cyanophora Paradoxa

Abstract

The cyanelles from the flagellated protist Cyanophora paradoxa constitute a plastid type sui generis. Cyanelles are surrounded by a murein layer and harbor a number of unusual genes in their 127 kbp genome (Wasmann et al., 1987). In this report a 12 kbp region will be described that contains a number of clustered genes encoding ribosomal proteins the complete sequence of which has been determined recently (Evrard et al., 1990a,b,c; Bryant and Stirewalt, 1990; Kraus et al., 1990; Michalowski et al., 1990; Bryant et al., 1990). Figure 1 depicts the central part of the large single copy region of cyanelle DNA from C. paradoxa 555 UTEX showing genes for 18 ribosomal proteins, one translation factor, ferredoxin I and two tRNAs. In addition two ORFs are present, the significance of which has yet to be determined. These genes appear to be organized in an Operon structure (str operon), a transcription unit comprising rpsl8 and rpl33 and a large gene cluster in which many genes from the prokaryotic S10 and spc operons are included. A comparison of the organization of these genes with those of cyanobacteria as the close relatives of cyanelles is possible to a limited degree only. The substantial progress in cyanobacterial molecular genetics during the past several years has been focussed mostly on the characterization of photosynthetic genes. Only for the str Operon data are available.