A cDNA fragment homologous to UDP-glucose dehydrogenase (UGD), which is known to be involved in the biosynthesis of pectin and hemicellulose through the conversion of UDP-glucose to UDP-glucuronic acid, was obtained by subtractive hybridization using RNA extracted from the fruits of the commercial and Japanese native peach cultivars with divergent fruit characteristics. The higher expression of the cDNA fragment in the fruits of the commercial cultivars was confirmed by Northern blot analysis. From the nucleotide sequence of the cDNA fragment, cDNA containing the entire coding region was cloned as a peach homolog of UGD, PpUGD1, and its deduced amino acid sequence was found to contain conserved regions important for UGD activity. The level of PpUGD1 mRNA in immature leaves was much higher than that in mature leaves. A change in the PpUGD1 mRNA level during peach fruit development corresponded to changes in the amount of cell wall material and the cell wall uronic acid content. These were greater in the fruits of the commercial cultivars compared with the Japanese native peach cultivars, and the expression of PpUGD1 was higher in the fruits of the commercial cultivars. These findings suggest a possible role of PpUGD1 in cell wall biosynthesis during peach fruit development.
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