Molecular Characterization of a Stable Antisense Chalcone Synthase Phenotype in Strawberry (Fragaria × ananassa)

• Published in: Journal of agricultural and food chemistry Vol. 54; no. 6; pp. 2145 - 2153
• Main Authors: Lunkenbein, Stefan, Coiner, Heather, de Vos, C. H. Ric, Schaart, Jan G, Boone, Marjan J, Krens, Frans A, Schwab, Wilfried, Salentijn, Elma M. J
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 22-03-2006
• Subjects: Acyltransferases - genetics; Agrobacterium tumefaciens; agrobacterium-mediated transformation; anthocyanins; antisense DNA; Biological and medical sciences; biosynthesis; Calypso; CHS gene; Cinnamates - analysis; dna microarrays; DNA, Antisense - genetics; Flavonoids - analysis; flavonols; flower color; Food industries; Fragaria; Fragaria - enzymology; Fragaria - genetics; Fragaria ananassa; Fruit - chemistry; Fruit and vegetable industries; Fundamental and applied biological sciences. Psychology; gene; gene dosage; gene expression; gene silencing; gene transfer; genetic recombination; Glucose - analysis; glycine-max; messenger RNA; ms detection; naringenin-chalcone synthase; phenolic-compounds; Phenotype; phenylpropanoids; plant polyketide biosynthesis; Plants, Genetically Modified - genetics; proanthocyanidins; RNA, Messenger - analysis; shoot regeneration; strawberries; transgenes; transgenic plants; phenylpropanoid; Acyltransferases; chalcone synthase; Fruit; Enzyme; Transferases; Fragaria x ananassa; Rosaceae; Fragaria ananassa; Acetate; p-coumaryl-1- acetate; Characterization; Phenotype; Naringenin-chalcone synthase; Dicotyledones; Strawberry; Angiospermae; Spermatophyta
• ISSN: 0021-8561; 1520-5118
• DOI: 10.1021/jf052574z

An octaploid (Fragaria × ananassa cv. Calypso) genotype of strawberry was transformed with an antisense chalcone synthase (CHS) gene construct using a ripening related CHS cDNA from Fragaria × ananassa cv. Elsanta under the control of the constitutive CaMV 35S promoter via Agrobacterium tumefaciens. Out of 25 transgenic lines, nine lines showed a reduction in CHS mRNA accumulation of more than 50% as compared to the untransformed cv. Calypso control. The antisense CHS construct was found to be integrated into the genome, with a copy number ranging from one to four. The pigmentation of the fruit was only affected when less than 5% of the control CHS expression level was detected. A stable antisense phenotype over a period of 4 years was obtained in the primary transgenic lines at a rate of 1:20. As a consequence of the reduced activity of CHS, the levels of anthocyanins, flavonols, and proanthocyanidins were downregulated and precursors of the flavonoid pathway were shunted to the phenylpropanoid pathway leading to highly increased levels of cinnamoyl glucose (520% of control), caffeoyl glucose (816% of control), and feruloyl glucose (1092% of control) as well as p-coumaryl alcohol (363% of control) and p-coumaryl-1-acetate (1079% of control), which occur only as trace components in untransformed control fruits. These results demonstrate that the introduction of an antisense CHS construct in strawberry results in an unpredictable biochemical phenotype, thereby confirming that CHS function is an important regulatory point of substrate flow between the flavonoid and the phenylpropanoid pathways. Keywords: Strawberry; Fragaria × ananassa; chalcone synthase; phenylpropanoid; p-coumaryl-1-acetate