Abstract: ObjectiveThe present study investigated the relationship between hormones and abscission of cotton boll to provide basic data on gene expression,regulation and function of abscission related genes.MethodThe cDNA of boll abscission layers treated by 50 mg/L gibberellin solution(GA3)and 250 mg/L ethephon solution(CEPA)respectively was used as Tester,while cDNA prepared from abscission layers which were treated with H2O was used as Driver. Subtractive library treated with GA3 and CEPA was constructed by suppression subtractive hybridization(SSH)technology and the EST sequence differentially expressed in abscission layer was selected by reverse Northern blotting. Then gene function annotation and function classification were carried out. The tissue expression patterns and GA3 induced expression patterns of the differentially expressed genes in boll abscission layer were analyzed.ResultThe Tester was the cDNA prepared from abscission layers treated with GA3,the Driver was the cDNA prepared from abscission layers treated with H2O. The constructed library was named GA library. The Tester was the cDNA prepared from abscission layers treated with CEPA, the Driver was the cDNA prepared from abscission layers treated with H2O. The constructed library was named GA library. Twenty-nine EST sequences differentially expressed in abscission layer were found in the two constructed subtractive li-braries(GA and CE)by sequence analyzed. Through gene function annotation and function classification,the EST se-quences were involved in translation,metabolism,signal transduction,transcription,protein synthesis,energy metabo-lism,stress defense,genome DNA and unknown function. The genes that related to translation accounted for 24.14%, which showed that there was a great deal of protein synthesis after hormonal treatment in abscission layer cells. Ten diffe-rentially expressed genes(EST sequence)from these libraries were analyzed by RT-PCR. It was found that the expression patterns of some genes changed after the cotton boll abscission layer was treated with GA3.ConclusionAfter hormone treatment,the abscission layer of cotton boll can activate the expression of abscission-related genes,thus affecting the ab-scission of organs,which is the result of their response to adversity stress.