Abstract: In order to illustrate the molecularmechanism of Co gene, which controls columnar tree structure in apple (Malus×domestica Borkh. ) , differential exp ression p rofile of cDNA among the columnar apple cultivar Waltz, the normal cultivar Fuji, and F₁ seedlings from the cross of Fuji ×Waltzwas analyzed through cDNA-AFLP. Sixty-four pairs of primers were used for the cDNA-AFLP amp lification. Totally 1 630 differentially expressed fragments between columnar and non-columnar app les were detected. Eleven differentially exp ressed fragmentswere confirmed by bulked segregant analysis (BSA) and reverse Northern blotting, further cloned and sequenced. Based on Database search, five cDNA fragments had high homologies to known genes,while the functions of other six were unknown. According to the alignment of Blastn and Blastx, one differentially exp ressed fragment, A7, was 97% identical in nucleotides to the 26S ribosomal RNA gene of Photinia fraseri and 91% in amino acids to cytochrome P450 monooxygenase in maize, respectively. Another differentially exp ressed fragment, A16, was 85% in nucleotides and 93% in amino acids identical to alpha-expansin 2 in Triphysaria versicolor. A16 and A7 as the candidate cDNA differential fragments, which may be related to tree architectures, were further analyzed by Northern Blotting. The express levels of them were the highest in Fuji and reduced gradually in the order of the no-columnar gene pool, columnar gene pool and Waltz. The results imp lied that the change of GA_S modulated by the cytochrome P450 monooxygenase genesmight influence the columnar growth habit.

Key words: Apple, Columnar apple, Co gene, Differential expression analysis, cDNA-AFLP