Ectopic Expression of a Pear (Pyrus bretschneideri) Dehydroascorbate Reductase Gene, PbrDHAR1, for Increased Ascorbate Content in Transgenic Tomato Plants

Abstract Dehydroascorbate reductase (DHAR EC 1.8.5.1) is a key enzyme involved in the recycling of AsA to dehydroascorbate (DHA). In order to increase AsA content of tomato, we developed transgenic tomato plants with PbrDHAR1 overexpression and the full-length cDNA encoding DHAR localized in the cytosol was isolated from Pyrus bretschneideri cv. Dangshansuli (PbrDHAR1) in this study. Successful incorporation in transgenic tomato plants was confirmed by PCR and quantitative reverse transcription PCR (qRT-PCR). PbrDHAR1 encoded a polypeptide of 213 amino acids with a predicted molecular mass of 52.7 kDa and shared 65–75 % sequence homology with DHAR from other plants. To explore the mechanism of AsA-GSH, we measured the accumulation of AsA in mature tomato fruit and analyzed gene expression patterns and enzyme activities. The overexpression of PbrDHAR1 increased DHAR activities and AsA contents in tomato fruits. These results revealed that cytosolic DHAR might contribute to increasing AsA contents of tomato.