Differential display of cotton cDNAs expressed by salicylic acid induction

Salicylic acid (SA) is very important in systemic acquired resistance and hypersensitive response in plant defense, and yet its role is not fully understood. This study seeks to clarify the mechanism of SA induced resistance in cotton. Total RNA was extracted from low gossypol cultivated cotton seedlings treated with exogenous SA and subjected to fluorescent differential display PCR (FDD PCR). Seven cDNA fragments were selected from the total ten differential bands. Comparison with Genbank database shows that all seven cDNA sequences are newly discovered in cotton. However, they share high amino acid identity to some registered cDNAs. Among them, three of the cDNAs could be predicted to encode basic chitinase, penicillin binding 6 b precursor and ATP dependent DNA helicase RecG, while the functions of the other four cDNAs are undetermined. Dot blot analysis demonstrates that the expression of five cDNAs in cotton seedlings is induced by SA, while SA induction has a negative effect on the transcript accumulation of the other two cDNAs (E13 and E14). Since SA was previously shown to enhance the resistance to cotton wilt disease, the finding of a basic chitinase gene in cotton expressed by SA induction will provide a new insight into induced disease resistance in cotton.