Development of Violet Transgenic Carnations and Analysis of Inserted Transgenes

Abstract

The pink, red and magenta colors in carnation flowers are due to the accumulation of pelargonidin and cyanidin-based anthocyanins. Carnations lack violet/blue flowers due to an absence of delphinidin-based anthocyanins, which are the dominant anthocyanins in most species having violet or blue flowers. The deficiency of delphinidin is attributed to the lack of the flavonoid 3′,5′-hydroxylase (F3′5′H) gene in carnation, the key gene for biosynthesis of delphinidin. Transgenic violet flower carnation varieties were generated by successful introduction and expression of a heterologous F3′5′H. Coexpression of a specific flavonoid biosynthesis gene or suppression of an endogenous gene involved in flavonoid biosynthesis was shown to enhance delphinidin accumulation. Some of the resultant transgenic carnation varieties have been commercialized in the USA, EU, Japan and other countries after obtaining the required permissions to release genetically modified organisms. Extensive molecular analysis of transgenic carnation is required by EU regulatory authorities and to a lesser extent in Japan. The analysis shows that the transgenic events often contain multiple transgenes and sometimes rearranged and/or partial T-DNA regions.