Isolation and characterization of genes expressed differently in mature fruits of 'redfield' and 'greensleeves' apples

Anthocyanins are responsible for most of the bright red and blue colors found in higher plants. Anthocyanin accumulation is regulated by MYB transcription factors. Some varieties of apple indicate anthocyanin accumulation with a red color in the skin and, at times, even in the cortex core, but other varieties without anthocyanin production have green-colored skin indicative of chlorophyll accumulation. To obtain gene expression profiles from the apple cultivars with different flesh and skin colors, 2 apple cultivars, the red-colored 'Redfield' and the green-colored 'Greensleeves', were used. A cDNA suppression subtractive hybridization library was established and analyzed. Six genes encoding methallothionein-like protein, chalcone isomerase, dirigent-like protein, brassinosteroid-6-oxidase, an unnamed protein product, and some unknown proteins were selected, and their expression was confirmed in the 'Redfield' cultivar through virtual northern blot analysis. In the 'Greensleeves' cultivar, 5 genes encoding gibberellins-regulated protein, a hypothetical 23.5 KD protein, anthranilate N-hydroxycinnamoyl/benzoyltransferase, and isoflavone reductase were chosen, and their upregulated transcriptional levels were identified. These selected genes were differently expressed in each apple cultivar, suggesting that these genes directly or indirectly regulate anthocyanin accumulation.