CHLOROPLAST DNA OF BLACK PINE RETAINS A RESIDUAL INVERTED REPEAT LACKING RIBOSOMAL-RNA GENES - NUCLEOTIDE-SEQUENCES OF TRNQ, TRNK, PSBA, TRNI AND TRNH AND THE ABSENCE OF RPS16

A physical map of black pine (Pinus thunbergii) chloroplast DNA (120 k b) was constructed and two separate portions of its nucleotide sequenc e were determined. One portion contains trnQ-UUG, ORF510, ORF83, trnK- UUU (ORF515 in the trnK intron), ORF22, psbA, trnI-CAU (on the opposin g strand) and trnH-GUG, in that order. Sequence analysis of another po rtion revealed the presence of a 495 bp inverted repeat containing trn I-CAU and the 3' end of psbA but lacking rRNA genes. The position of t rnI-CAU is unique because most chloroplast DNAs have no gene between p sbA and trnH (trnI-CAU is usually located further downstream). Black p ine chloroplast DNA lacks rps16, which has been found between trnQ and trnK in angiosperm chloroplast DNAs, but possesses ORF510 instead. Th is ORF is highly homologous to ORF513 found in the corresponding regio n of liverwort chloroplast DNA and ORF563 located downstream from trnT in Chlamydomonas moewusii chloroplast DNA. A possible pathway for the evolution of black pine chloroplast DNA is discussed.