Introns in chloroplast protein-coding genes of land plants.

Several protein-coding genes from land plant chloroplasts have been shown to contain introns. The majority of these introns resemble the fungal mitochondrial group II introns due to considerable nucleotide sequence homology at their 5' and 3' ends and they can readily be folded to form six hairpins characteristic of the predicted secondary structure of the mitochondrial group II introns. Recently it has been demonstrated that some mitochondrial group II introns are capable of self-splicing in vitro in the absence of protein co-factors. However evidence presented in this overview suggests that this is probably not the case for chloroplast introns and that trans-acting factors are almost certainly involved in their processing reactions.