Enhancement of Reporter-Gene Expression by Insertions of Two Introns in Maize and Tobacco Protoplasts

Abstract

The effects of two-intron insertions on reporter-gene expression were examined in transient assays in maize and tobacco. The first introns of a rice gene for phospholipase D (PLD), a maize gene for ubiquitin and a castor bean gene for catalase were tested with a gene for β-glucuronidase (GUS) or a gene for luciferase driven by a cauliflower mosaic virus 35S promoter (35S-GUS or 35S-Luc), the promoter of the maize ubiquitin (Ubi-GUS) or the promoter of a maize pyruvate, orthophosphate dikinase (PPDK-GUS). Although the enhancing effect varied, several intron combinations synergistically enhanced the reporters. When the first and second introns of the PLD gene were inserted in tandem, the reporter was synergistically enhanced. These results imply that expression enhancement by two introns may be observed in wide combinations of promoters, introns, and structural genes and that such enhancement plays certain roles in regulation of gene expression in higher plants.