Abstract
AbstractIn general, carnations (Dianthus caryophyllus) have each of four kinds of anthocyanins acylated by malic acid. A few carnation cultivars are known to display a peculiar dusky color supposedly caused by anthocyanic vacuolar inclusions (AVIs). The hereditary pattern suggests that the peculiar color is controlled by a single recessive factor tightly linked with existence of AVIs containing non-acylated anthocyanins. To diversify the peculiar color carnation, we produced a bluish purple line displaying a highly novel metallic appearance by crossbreeding. By subjecting the line to ion-beam irradiation, we generated metallic reddish purple, metallic crimson and metallic red lines. The major anthocyanin of the metallic bluish purple and reddish purple lines was pelargonidin 3,5-diglucoside, whereas that of the metallic crimson and red lines was pelargonidin 3-glucoside. All four metallic lines did not have transcripts for anthocyanin malyltransferase. Metallic crimson and red lines did not express the acyl-glucose-dependent anthocyanin 5-O-glucosyltransferase gene. In contrast to the dusky color types, metallic lines have highly condensed AVIs and water-clear vacuolar sap in the petal adaxial epidermal cells. Differences in the number of AVIs on the abaxial side were observed within mutants containing the same anthocyanin, thereby affecting their shade and hue. We demonstrated that (1) a factor generating the AVIs is inactivated anthocyanin malyltransferase gene, (2) AVIs in water-clear vacuolar sap in the adaxial epidermal cells generate the novel metallic appearance, and (3) ion beam breeding is a useful tool for increasing metallic colors by changing anthocyanin structure and the level of AVIs.
Highlights
Carnation (Dianthus caryophyllus) is one of the most important horticultural crops around the world
Petal epidermal cells of the ten randomly chosen peculiar color plants from each of the latter three crossings were microscopically examined, revealing that all of them had anthocyanic vacuolar inclusions (AVIs) in their petal epidermal cells. These facts are consistent with the hypothesis that the peculiar color phenotype is conferred by AVIs formation, which is controlled by a single recessive allele
Aiming to rationally diversify peculiar colors in carnation, we attempted to elucidate the hereditary pattern of the peculiar color phenotype and to identify genes involved in color expression
Summary
Carnation (Dianthus caryophyllus) is one of the most important horticultural crops around the world. Four major anthocyanins are known in carnation: pelargonidin 3-malylglucoside (Pg3MG), cyanidin 3-malylglucoside (Cy3MG), pelargonidin 3,5-cyclicmalyldiglucoside (Pg3,5cMdG), and cyanidin 3,5-cyclicmalyldiglucoside (Cy3,5cMdG) (Bloor 1998; Nakayama et al 2000). All of these anthocyanins are glycosylated and are normally acylated by malic acid. Violet carnations accumulating delphinidin have been produced by genetic engineering (Tanaka and Ohmiya 2008), we have chosen another path to achieve novel carnation colors with non-genetically modified organisms. The structural simplicity of anthocyanin constituents makes it laborious to produce novel flower colors in carnation. The fact that wild Dianthus species and their relatives have the same anthocyanins as those found in carnation cultivars increases the difficulty in enriching flower color variation by crossing carnation cultivars with wild Dianthus species and relatives
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