RNA editing in hornwort chloroplasts makes more than half the genes functional

RNA editing in chloroplasts alters the RNA sequence by converting C‐to‐U or U‐to‐C at a specific site. During the study of the complete nucleotide sequence of the chloroplast genome from the hornwort Anthoceros formosae, RNA editing events have been systematically investigated. A total of 509 C‐to‐U and 433 U‐to‐C conversions are identified in the transcripts of 68 genes and eight ORFs. No RNA editing is seen in any of the rRNA but one tRNA suffered a C‐to‐U conversion at an anticodon. All nonsense codons in 52 protein‐coding genes and seven ORFs are removed in the transcripts by U‐to‐C conversions, and five initiation and three termination codons are created by C‐to‐U conversions. RNA editing in intron sequence suggests that editing can precede intercistronic processing. The sequence complementary to the edited site is proposed as a distant cis‐recognition element.