Localization of two novel chloroplast genome functions: trans-splicing of RNA and protochlorophyllide reduction

Summary Chloroplast DNA deletions in the unicellular green alga Chlamydomonas reinhardtii localize two novel chloroplast gene functions. One of these, tscA, is required in trans for splicing, in trans, of the first and second, but not the second and third, exons of the RNA of the chloroplast gene psaA. Previously, no chloroplast genes were known to be required in trans for the splicing of chloroplast RNA. The other chloroplast gene function is required for light-independent reduction of protochlorophyllide, a key step in the algal pathway of chlorophyll biosynthesis. Both functions reside in the same 4 kbp region of chloroplast DNA.