Abstract: To investigate the function of acyl-CoA-binding protein in Malus domestica，we isolated a new ACBP gene（designated as MdACBP2） from leaf cDNA using RACE technique. The full-length cDNA has an open reading frame（ORF） of 378 bp encoding a protein of 125 amino acids. The putative amino acid sequence contains an ACB domain consisting of 85 amino acid residues as predicted with  SMART program. Sequence analysis and structural feature indicated that MdACBP2 belongs to Class Ι of ACBP family. Quantitative real-time PCR experiment revealed that MdACBP2 is expressed in root，leaf，flower，young fruit，bark and bud. The highest mRNA expression was found in leaf，and the lowest in young fruit. The responses of MdACBP2 expression to biotic or abiotic stress were also investigated using quantitative real-time PCR. The results showed that MdACBP2 expression was inhibited by osmotic stress and Botryosphaeria dothidea infection，but was enhanced by cold stress. There was no significant changes among the apple seedlings treated with 1 mmol · L^-1 Pb(NO₃)₂. It was speculated that MdACBP2 gene might be involved in the defense of apple seedling against cold stress.

Key words: Malus domestica, acyl-CoA-binding protein, Botryosphaeria dothidea, cold stress, osmotic stress