Sequencing and characterization of a cDNA encoding a ferritin subunit of Colorado potato beetle, Leptinotarsa decemlineata

A differentially expressed cDNA fragment (P311) from Colorado potato beetle (CPB), Leptinotarsa decemlineata (Say), was identified by restriction fragment differential display-polymerase chain reaction (RFDD-PCR) technique, and showed a strong similarity to ferritin heavy chain subunits of other organisms. Based on P311, we constructed specific primers and obtained a 840-bp cDNA fragment spanning the open reading frame of CPB ferritin subunit using the rapid amplification of cDNA ends (RACE) technique. The sequence encodes 213 amino acid residues, including a 19 amino acid signal peptide. The sequence has a conserved cysteine in the N-terminus and has the seven conserved residues that comprise the ferroxidose center, which is the feature of heavy chain ferritins of vertebrates. The CPB ferritin subunit has high amino acid sequence identity with the Apriona germari (69.3%), Golleria mellonela (54.5%), Monduca sexto (54.0%), Drosophila melanogaster (53.2%), Coloodes ethlius (51.4%), and Nilaparvata lugens (47.6%) but lower identity with the Anopheles gombiae (38.7%) and Aedes aegypti (37.8%). Using Northern blot analysis, the subunit mRNA was identified from fat body and midgut of 4th instars with much higher mRNA levels found in midgut than that in fat body (similar to 2.5fold). Nevertheless, only the levels of mRNA in fat body was induced by dexamethasone (similar to 1.5-fold).