Abstract
The ndhK gene encodes a subunit of the chloroplast NADH dehydrogenase, and is co-transcribed with the adjacent ndhC and J genes on the tobacco chloroplast genome. The ndhK gene product is translated from polycistronic mRNAs but not from monocistronic ones. According to tobacco chloroplast in vitro translation analyses, we defined that the major initiation site of tobacco ndhK cistron is the AUG codon that located 4 nt upstream from the ndhC stop codon, and ndhK translation depends exclusively on ndhC termination codon. Removal of the ndhC 5' UTR still supported substantial translation of ndhK cistron. This result suggested that ndhK cistron should be translated by an additional unknown mechanism in addition to translational coupling in a termination codon-dependent mannar.
