Ectopic Expression of Oncidium Gower Ramsey Phytoene Synthase Gene Caused Pale Flower and Reduced Leaf Size in Transgenic Tobacco

Abstract

Oncidium Gower Ramsey is an important orchid for cut flower production and export in Taiwan. The bright yellow flower color of Oncidium Gower Ramsey is due to the accumulation of carotenoids. The phytoene synthase (PSY) gene, a key enzyme for the biosynthesis of carotenoids was cloned, by isolating total RNA from labellum and reverse transcription followed by polymerse chain reaction. A full-length sequence of the Oncidium PSY cDNA (OncPSY) was obtained by rapid amplification of cDNA ends (RACE). Phylogenetic analysis revealed evolutionary conservation of the encoding OncPSY protein sequence. RT-PCR analysis showed that OncPSY was highly expressed in flowers and leaves, but less in roots. Ectopic expression of 35S::OncPSY in tobacco plant resulted in severe phenotypic effects including dwarfing, altered leaf morphology, and reduced flower color.