Expression of a C3 plant Rubisco SSU gene in regenerated C4 Flaveria plants

Abstract

We report the successful transformation, via Agrobacterium tumefaciens infection, and regeneration of two species of the genus Flaveria: F. brownii and F. palmeri. We document the expression of a C3 plant gene, an abundantly expressed ribulose 1,5-bisphosphate carboxylase/oxygenase small subunit gene isolated from petunia, in these C4 plants. The organ-specific expression of this petunia gene in Flaveria brownii is qualitatively identical to its endogenous pattern of expression.

Genetic transformation of the C4 plant, Flaveria bidentis

“…Martineau et aL (1989) reported the transformation of two C4-1ike Flaveria species using Agrobactedum infection of mature leaf explants followed by regeneration of transformed shoots from callus. Shoots were regenerated on Murashige and Skoog medium containing 4 mg 1-1 6-(7-~,-dimethylallylamino)purine (2iP) and 1 mg 1-1 indole acetic acid (IAA).…”

“…The ability to compare closely related species with different physiological properties and different programmes of gene regulation should be a helpful experimental approach. Martineau et al (1989) reported the transformation of two C4-1ike intermediate species, Flaveria palmeri and F. brownii, suggesting that C4 Flaveria species might be good candidates for transformation. F. bidentis is a fully C4 species with a wide geographic distribution, probably native to South America (Powell, 1987).…”

Developmental Genetics of C4 Photosynthesis

“…C4 genes have been introduced into C3 plants and vice versa with mixed success. A petunia (C3) rbcS gene was transcrip tionally active when introduced into F. brownii (C4-like), although cell localization was not described (91). The maize C4 ppc, ppdk and rbcS promoters drive transcription of a GUS reporter gene in leaf mesophyll and other photosynthetic cells of transgenic tobacco (99).…”

Maize rbcS promoter activity depends on sequence elements not found in dicot rbcS promoters.

“…In contrast, dicot but not monocot rbcS promoters are expressed in C3 dicot cells (Keith and Chua, 1986; this study). In a C4 dicot plant flaveria, a C3 dicot rbcS promoter (petunia) is active after transformation (Martineau et al, 1989). The upstream silencers of maize rbcS revealed in protoplast transient expression might be important for mesophyll-specific repression.…”