Isolation,cloning, and expression of five genes related to nitrogen metabolism in peach (Prunus persica L. Batsch)

An optimal dosage of nitrogen has long been known to play important roles in governing nitrogen-use efficiency and improving the yield of plants. However, there is limited information on the isolation and expression profiles of genes related to nitrogen metabolism in peach (Prunus persica L. Batsch). This study isolated five genes involved in nitrogen metabolism and evaluated the effects of a single foliar application of urea on levels of expression of these genes in the leaves of ‘Dazhenbaochiyue’ peach. Cloning resulted in the isolation of 1,767, 1,236, 1,074, 1,758, and 2,721 nt-long cDNAs with full-length open reading frames encoding 588, 411, 357, 585, and 906 amino acids representing the asparagine synthetase (AS), glutamate dehydrogenase (GDH), glutamine synthetase (GS), nitrite reductase (NiR), and nitrate reductase (NR) genes in peach, respectively. An alignment of multiple amino acid sequences revealed that the AS, GDH, GS, and NR proteins in peach shared high levels of sequence conservation or identity at the amino acid level with their homologues in Arabidopsis thaliana and grapevine (Vitis vinifera). Based on analyses of expression of the five genes in peach leaves, we demonstrated that genes related to nitrogen metabolism responded to a foliar application of urea within 2 d. This was consistent with previous reports which indicated that leaves rapidly absorbed urea-nitrogen after foliar application. Foliar application of 0.5% (w/v) urea inhibited expression of GS and NiR, but increased expression of GDH, AS, and NR compared to control leaves. The different patterns of expression of the five genes in this study suggested that their expression might reflect their various roles in nitrogen metabolism, plant N status, and responses to weather conditions such as high light intensity, temperature, or humidity, all of which affect photosynthesis. These findings provide a basis for future functional analyses of these five genes in peach.