Expression of the ndhCKJ operon of barley and editing at the 13th base of the mRNA of the ndhC gene

We have determined a 1778 base sequence which includes the complete ndhCKJ operon of barley plastid DNA. This operon contains the ndhC, ndhK and ndhJ genes encoding the polypeptides NDH-C, NDH-K and NDH-J, respectively, of the thylakoid Ndh complex. Poly-and mono-cistronic transcripts were identified, with an increase in the latter under oxidative stress induced by herbicide Paraquat. Complete sequencing of transcript cDNAs and of the corresponding regions of five additional monocots revealed that the 13(th) C (cytosine) base of ndhC is edited to U (uracil) converting the CAC codon (encoding histidine, H) to UAC (encoding tyrosine, Y). Dicots having the appropriate TAC codon at the genome sequence do not require editing. The new editing site can not be predicted by comparison with the Marchantia sequence (that has a C at the 13(th) position) because, in contrast to Angiosperms, the amino-terminal sequence in lower plants is highly variable in NDH-C.