The impact of AUG start codon context on maize gene expression in vivo.

In mammals, the sequence context surrounding an AUG start codon can alter the efficiency at which translation is initiated. Less is known about the AUG context requirements for translation initiation in plants. Using a maize transient assay, we present evidence that the naturally occurring AUG start codon of the Alcohol dehydrogenase-1 is efficiently used in vivo. We have also tested the effects of upstream, out-of-frame AUGs on the translation of firefly luciferase reporter gene mRNAs. The presence of an upstream out-of-frame AUG, even when surrounded by a 'poor' context, eliminated most luciferase expression, suggesting efficient translation initiation at the upstream AUG. The relaxed requirements for AUG context in maize suggest that plants and mammals may differ in their requirements for efficient translation initiation.