Intron-specific stimulation of anaerobic gene expression and splicing efficiency in maize cells

Most of the glyceraldehyde-3-phosphate dehydrogenase (GAPDH) genes characterized in plants and algae to date have one intron very close to the 5 end of the gene. To study the functional relevance of some of these introns for gene expression we have analysed the influence of three 5 introns on transient gene expression of the anaerobically inducible maizeGapC4 promoter in maize cells. Under aerobic conditions, reporter gene expression is increased in the presence of the first introns of theGapC4 andGapC1 genes, and the first intron of the nuclear encoded chloroplast-specificGapA1 gene. In contrast, theGapC4 intron increases anaerobic gene expression above the level obtained for the intronless construct, while anaerobic expression of constructs harboring theGapA1 andGapC1 introns was similar to the anaerobic expression level of the intronless construct. Splicing analysis revealed that theGapC4 intron is processed more efficiently under anaerobic conditions, while no change in splicing efficiency is observed for theGapC1 and theGapA1 introns when subjected to anaerobic conditions. These results suggest that an increase in splicing efficiency contributes to the anaerobic induction of the maizeGapC4 gene.