T10 GM chrysanthemum was developed by Agrobacterium tumefaciens-mediated transformation of wild type cultivar T10 (Flower type Decorative) with the binary vector pB423. Aim of the modifications is flower colour modification. The inserted T-DNA contains:

• The introduced F3’5’H gene which encodes a flavonoid 3’,5’-hydroxylase enzyme from Campanula medium. This enzyme converts a precursor molecule of pink to red cyanidin-based pigments in chrysanthemum into a precursor molecule of purple to blue delphinidin-based pigments. Introduction of the specific F3’5’H gene cassette used in the GM chrysanthemum lines was reported to convert up to 95% of cyanidin-type pigments in petals to delphinidin-type pigments.

• The A3’5’GT gene which encodes a UDP (uridine diphosphate)-glucose:anthocyanin 3′,5′-O-glucosyltransferase enzyme from Clitoria ternatea. This enzyme efficiently glucosylates both cyanidin-type and delphinidin-type pigments. GM chrysanthemum petals containing 95% 3’5’-glucosylated delphinidin-type pigments were found to be blue in colour. In comparison, petals without expression of the A3’5’GT gene, which contained only delphinidin-type pigments without 3’5’-glucosylation, were purple in colour.

• The introduced nptII gene used as a selectable marker.

Expression of both the F3’5’H gene and the A3’5’GT gene is controlled by the F3H promoter from chrysanthemum. This promoter is reported to be petal-specific, supported both by its natural role in controlling a flower pigment biosynthesis gene and by experimental evidence that it drives transgene expression in petals, but not in leaves or stems.

Stable expression of the introduced genetic modification through generations is demonstrated by maintenance of the flower colour phenotype. Southern blot analysis indicated that T10 GM chrysanthemum contains two copies of the T-DNA. It is unclear whether each insertion is a complete or partial copy.

Sources:

1. Noda et al. (2013), Genetic Engineering of Novel Bluer-Colored Chrysanthemums Produced by Accumulation of Delphinidin-Based Anthocyanins. Plant Cell Physiology 54(10): 1684–1695
2. DIR191 - Risk assessment and Risk Management Plan; Australian Government, Office of the Gene Technology Regulator