Abstract: The apidermin (APD) family, named after three cuticular proteins (apidermin 1-3, APD 1-3) in the Western honeybee, Apis mellifera, is a novel insect structural cuticular protein family. A hypothetical gene locus (LOC727145) was found to be located at the upstream of the reported apd gene cluster in the honeybee genomic sequence. In order to characterize this gene, we mapped its transcription start sites (TSSs) by a group of 5′ LongSAGE tag sequences, and subsequently cloned its cDNA sequences through RT-PCR by using three different 5′LongSAGE tag sequences as the up-stream primers. The cloned cDNA sequences were submitted to GenBank under the accession numbers GU358197, GU358198 and GU358199. Bioinformatics analysis revealed that the genomic DNA sequence LOC727145 contains two exons and one intron, where the boundary conforms to the GU/AG rule. The cDNA sequence is extremely GC-rich (70%), and the deduced protein is highly hydrophobic. Five amino acids （Ala, Gly, Pro, Leu and Val） account for 77% of the deduced polypeptide sequence,  and Ala is the most abundant residue (29％). These characters are comparative to APD 1-3. Moreover， the deduced polypeptide sequence has 50% identity with APD-1 protein, and both possess a similar predicted hydrophobic signal peptide at the N-terminal. These results suggest that LOC727145 encodes a novel APD protein. The mapping result of 5′ LongSAGE tag sequences on genome sequence showed that LOC727145 was highly expressed in drone head, and RNA PolⅡ initiated transcription of this gene at six alternative TSSs with different efficiency, and 90% of the mRNA molecules came from a dominant TSS. This research identified a novel apidermin protein, named apidermin-like (apd-like).

Key words: Apis mellifera, 5′LongSAGE, cuticular protein, apd-like gene, transcription start site (TSS)