Abstract: 4-coumarate co-enzyme A ligase（4CL） gene is a gene family in the plants. It is responsible for biosynthesis of flavonoides and lignin. A group of 4CL-like genes have been discovered from the genomic database of Citrus clementina. Analysis of their protein structures indicated that only three genes possessed typical characters of 4CL family. Phylogenetic relationship analysis divided those three citrus Cit4CL genes into two groups：ClassⅠand ClassⅡ. Gene expression profiles in Meyer lemon[C. limon（L.）Burm. f.] demonstrated a tissue-specific and temporal-specific fashion. The expression of Cit4CL1 was highly positively correlated with the concentration of flavonoids，indicating that this gene is important in the biosynthesis of flavonoids. However，the expression of the Cit4CL2 and Cit4CL3 genes did not relate to the flavonoids contents，but showed strong relationship with the tissues where the lignin biosynthesis occur red. This suggested that those two genes could be involved in the lignification. This study provided the basic information on function of 4CL family genes in citrus.

Key words: Citrus, 4CL, bioinformatic analysis, flavonoids, lignin, expression