Molecular characterization of the gene encoding rice allene oxide synthase and its expression.

The gene encoding rice allene oxide synthase, OsAOS, was intronless and had nucleotide sequences with the high GC content of 67%. Deduced amino acid sequences had very high similarity with other AOS proteins, in particular 74% similarity to barley, characterized by the conserved motifs of P450 cytochrome of the CYP74A family. Purified recombinant rice AOS protein expressed in Escherichia coli converted 13-hydroperoxylinolenic acid to allene oxide. Several restriction enzyme digestions and Southern analysis showed that OsAOS was likely to have two copies in its genome. The basal level of OsAOS expression was detected in various tissues and the transcription level was increased by jasmonate treatment.