DNA Structure Analysis of Chitinase Gene Clone RCH8 from Rice

RCH8 is a basic chitinase genomic clone isolated from rice (var. IR36) genomic library using a bean chitinase gene fragment as a probe. The complete nucleotide sequence was determined in both directions by the dideoxy chaintermination method. Deletions of the DNA chain for sequencing were created by exonuclease Ⅲ and S1 nuclease (Fig. 1 ). The 2049 bp clone contains a 1057 bp upstream sequence and a single, complete open reading frame of 966 bp with no introns (Fig. 2 ). The 5' side sequence contains possible regulatory elementS (Table 1 ). The ORF encodes a polypeptide of 322 amino acids with a putative 20 amino acid Nterminal signal peptide followed by a 40 amino acid cysteine-rich domain contuining 8 cystein residues and a chitinase catalytic domain. The deduced amino acid sequence shares 88. 5%, 80. 4 % and 78. 9% identity with those of three other published basic chitinase genes from rice(Table 2,Fig. 3). In addition, the hevein domain sequence homologies of nucleic acids and amino acids were compared between RCH8 and several other proteins(Table 3, Fig.4 ).