YABBY family proteins are plant-specific transcriptional factors. YABBY genes can be divided into three subfamilies. Within the CRC/DL subfamily, the Arabidopsis CRC (CRABS CLAW) and the rice DL (DROOPING LEAF) have functionally diverged in the control of leaf development. CRC has no function in leaf development, while DL plays an important role in the formation of leaf midribs. In this study LiYAB1, an ortholog of CRC/DL genes from lily (Lilium longiflorum), was isolated by screening a cDNA library derived from young lily flower buds. Subcellular localization analysis indicated that LiYAB1 is nuclear localized. LiYAB1 is expressed strongly in the carpels of the lily flower and weakly in the leaves, which is similar to DL in rice. Ectopic expression of LiYAB1 in the rice dl mutant could rescue the drooping leaf phenotype of dl in some of the transgenic rice plants and cause abnormal leaves in the other transgenic plants. The overexpression of LiYAB1 in the wild-type Arabidopsis caused leaf abnormality. The results suggest that LiYAB1, a member of the CRC/DL subfamily genes, might have an important function in regulating the leaf development in lilies, as DL does in rice.