Molecular characterization of a gene for alanine aminotransferase from rice (Oryza sativa)

A cDNA clone encoding alanine aminotransferase (AlaAT) has isolated from ra ndomly sequenced clones derived from a cDNA library of maturing rice seeds by comparison to previously identified genes. The deduced amino acid sequen ce was 88% and 91% homologous to those of the enzymes from barley and broom corn millet (Panicum miliaceum), respectively Using this cDNA as a probe, w e isolated and sequenced the corresponding genomic clone. Comparison of the sequences of the cDNA and the genomic gene revealed that the coding region of the gene was interrupted by 14 introns 66 to 1547 bp long. Northern and western blotting analyses showed that the gene was expressed at high level s in developing seeds. When the 5'-flanking region between -930 and +85 fro m the site of initiation of transcription was fused to a reporter gene for beta-glucuronidase (GUS) and then introduced into the rice genome, histoche mical staining revealed strong GUS activity in the inner endosperm tissue o f developing seeds and weak activity in root tips. Similar tissue-specific expression was also detected by in situ hybridization. These results sugges t that AlaAT is involved in nitrogen metabolism during the maturation of ri ce seed.