Abstract
BackgroundThere are many non-cereal monocots of agronomic, horticultural, and biofuel importance. Successful transformation of these species requires an understanding of factors controlling expression of their genes. Introns have been known to affect both the level and tissue-specific expression of genes in dicots and cereal monocots, but there have been no studies on an intron isolated from a non-cereal monocot. This study characterizes the levels of GUS expression and levels of uidA mRNA that code for β-glucuronidase (GUS) expression in leaves of Gladiolus and Arabidopsis using GUBQ1, a polyubiquitin promoter with a 1.234 kb intron, isolated from the non-cereal monocot Gladiolus, and an intronless version of this promoter.ResultsGladiolus and Arabidopsis were verified by Southern hybridization to be transformed with the uidA gene that was under control of either the GUBQ1 promoter (1.9 kb), a 5′ GUBQ1 promoter missing its 1.234 kb intron (0.68 kb), or the CaMV 35 S promoter. Histochemical staining showed that GUS was expressed throughout leaves and roots of Gladiolus and Arabidopsis with the 1.9 kb GUBQ1 promoter. GUS expression was significantly decreased in Gladiolus and abolished in Arabidopsis when the 5′UTR-intron was absent. In Arabidopsis and Gladiolus, the presence of uidA mRNA was independent of the presence of the 5′UTR-intron. The 5′-UTR intron enhanced translation efficiency for both Gladiolus and Arabidopsis.ConclusionsThe GUBQ1 promoter directs high levels of GUS expression in young leaves of both Gladiolus and Arabidopsis. The 5′UTR-intron from GUBQ1 resulted in a similar pattern of β-glucuronidase translation efficiency for both species even though the intron resulted in different patterns of uidA mRNA accumulation for each species.
Highlights
There are many non-cereal monocots of agronomic, horticultural, and biofuel importance
Southern hybridization Gladiolus and Arabidopsis plants were transformed with the uidA gene under control of either a 1.9 kb GUBQ1 promoter (G1-1), a 5′end of GUBQ1 that is lacking the intron (G1-3), or the CaMV 35 S promoter (Figure 1)
Gladiolus plant lines transformed with the uidA gene under control of either G1-3 or CaMV 35 S were multicopy with 4–7 and 3–7 copies, respectively, of the transgene
Summary
There are many non-cereal monocots of agronomic, horticultural, and biofuel importance. There are many non-cereal monocots of agronomic (garlic, onions, banana, sugarcane, millet), horticultural (turf and forage grasses such as tall fescue, Kentucky bluegrass, creeping bentgrass, perennial ryegrass, St. Augustinegrass, buffalograss, Zoysiagrass japonica, Paspalum vaginatum, Paspalum notatum, floral crops such as orchids, lilies, tulips, crocus, amaryllis, iris), and potential biofuel (switchgrass, Miscanthus) importance. Augustinegrass, buffalograss, Zoysiagrass japonica, Paspalum vaginatum, Paspalum notatum, floral crops such as orchids, lilies, tulips, crocus, amaryllis, iris), and potential biofuel (switchgrass, Miscanthus) importance Successful transformation of these species requires an understanding of how their gene expression is controlled by promoter elements such as introns. There have been a few transient transformation studies showing IME of non-cereal monocots (banana, lily, bluegrass) using introns (maize Ubi, Arabidopsis UBQ) isolated from either cereal monocots or dicots [11,12,13,14]. Half of the introns tested by Vain et al [12] showed different results on transient expression for maize and bluegrass indicating a difference between cereal and non-cereal monocots
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