A novel chitinase gene (GhChia7 ) was isolated from salicylic acid (SA)-treated cotton cotyledons and characterized by DNA sequence analysis of its cDNA and genomic DNA clone. The deduced amino acid sequence, designated as class Ⅶ chitinase, shares about 30% identity to class Ⅰ or Ⅱ chitinases, and does not correspond to any of the previously characterized classes Ⅰ-Ⅵ chitinases. Northern blotting analysis showed that the transcripts of GhChia7 were abundant both in cotton fibers and in the roots of the seedlings. The accumulation of GhChia7 mRNA in SA-treated cotyledons reached maximum at 7.5 mmol/L concentration after 18 h. Results indicate that GhChia7 might play an important role in cotton抯 active defense response.
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