THE ATPF GROUP-II INTRON-CONTAINING GENE FROM SPINACH-CHLOROPLASTS ISNOT SPLICED IN TRANSGENIC CHLAMYDOMONAS CHLOROPLASTS

In order to determine whether the group-II trans-splicing machinery of the chloroplast of Chlamydomonas reinhardtii can splice a heterologou s group-II cis intron, the atpF gene of spinach was transferred into t he chloroplast genome of C. reinhardtii using the atpX expression vect or. The atpF gene contains a group-II intron which, like other higher plant chloroplast introns, does not self-splice in vitro. The chimeric transgene was expressed at high levels, based on the accumulation of the precursor; however, spliced products could not be detected by Nort hern blotting, or by RT-PCR coupled with Southern-blot hybridization o f the amplified products with an exon-junction probe. These results in dicate that the spinach atpF intron is not spliced in transgenic C. re inhardtii chloroplasts. Thus, splicing of chloroplast introns mediated by cellular factors may be species-specific; alternately, the group-I I splicing machinery of C, reinhaudtii is specific for trans-spliced i ntrons.