Tissue specificity and expression level of gusA under rolD, mannopine synthase and translation elongation factor 1 subunit a promoters in transgenic Gladiolus plants

Abstract

Transgenic plants of Gladiolus cv. Jenny Lee were developed that contain the bargusA fusion gene under either the mannopine synthase 2 (mas2), translation elongation factor 1 subunit α (EF-1α), rolD, or the cauliflower mosaic virus 35S (CaMV 35S) promoters. The relative level of gusA expression in leaves of five to ten independently transformed, in-vitro-grown plants representing each promoter was similar for transgenic plants containing the rolD and CaMV 35S promoter and 2.0-fold and 3.3-fold higher than the level for the mas2 and EF-1α promoters, respectively. The maximum level of gusA specific activity by leaves was 135–173 nmol 4-methylumbelliferone (4-MU)/h per milligram protein for plants containing either CaMV 35S or rolD as compared to only 27–38 nmol 4-MU/h per milligram protein for plants with either mas2 or EF-1α. Histochemical staining confirmed the relatively high level of gusA expression throughout the length of the older, 6-cm-long leaves of plants that contained bargusA under rolD, whereas gusA expression was infrequently observed throughout the older leaves of plants containing either the mas2 or EF-1α promoters. In contrast to the older leaves, staining showed that strong gusA expression was frequently observed throughout young leaves of plants with either the mas2, EF-1α, or rolD promoters. Roots of plants with the rolD and EF-1α promoters showed strong gusA expression specifically in 93% and 68%, respectively, of the root tips. Roots of the plants with the mas2 promoter showed strong gusA expression throughout the entire length of the root.