Abstract: Chrysanthemum（Chrysanthemum morifolium Ramat.）cultivar‘Xingguang Canlan’with cold resistance was used as experimental materials in this study，ω-3 fatty acid desaturase gene were separated and cloned from the leaf by RT-PCR and RACE，named CmFAD7，accession number is KC567246 in GenBank. The full length cDNA of CmFAD7 is 1 284 bp，encoding a protein of 428 amino acids. Its molecular mass is 48.98 kD，and pI is 9.07. The identities of putative amino acid sequence of chrysanthemum ω-3 fatty acid desaturase compared with that of plastidial ω-3 fatty acid desaturase from Crepis alpine is 84%. CmFAD7 protein contains a delta 12-FADs conservative domain，three transmembrane helical structures，and a chloroplast transit peptide at N-terminal，which is belonging to the Membrane-FADs-like superfamily. Expression of CmFAD7 and fatty acid content in leaf and root under low temperature stress were determined with real-time fluorescent quantitative PCR and gas chromatographytechnology，CmFAD7 expressed in root and leaf under different temperatures，the level of expression in leaves was higher than that in roots. The highest expression level in roots and leaves were at 5 ℃，–4 ℃，respectively. Oppositely，the expression level in leaves and roots were lower at–8 ℃. With the decline of treatment temperature，C18:3 content in leaves increased gradually，but there is no obvious changes in roots. In conclusion，CmFAD7 is associated with the cold resistance in chrysanthemum，there are significant differences for expression level in different organs under the conditions of low temperature.

Key words: chrysanthemum, unsaturated fatty acid, CmFAD7, expression analysis