The Arabidopsis chloroplast ribosomal protein L21 is encoded by a nuclear gene of mitochondrial origin

Many chloroplast genes of cyanobacterial origin have been transferred to th e nucleus during evolution and their products are re-addressed to chloropla sts. The RPL21 gene encoding the plastid r-protein L21 has been lost in hig her plant chloroplast genomes after the divergence from bryophytes. Based o n phylogenetic analysis and intron conservation, we now provide evidence th at in Arabidopsis a nuclear RPL21c gene of mitochondrial origin has replace d the chloroplast gene. The control of expression of this gene has been ada pted to the needs of chloroplast development by the acquisition of plastid- specific regulatory promoter cis-elements. (C) 2001 Elsevier Science B.V. A ll rights reserved.