Transcriptional regulation of ferritin mRNA levels by iron in the freshwater giant prawn, Macrobrachium rosenbergii

Ferritin, a major iron storage protein of most living organisms，plays a crucial role in iron metabolism. A cDNA encoding a heavy-chain homologue of ferritin was isolated and sequenced in the freshwater giant prawn, Macrobrachium rosenbergii. The cloned cDNA was 1012 bp long containing an iron-responsive element (IRE) sequence in the 5′-untranslated region and a complete open-reading frame encoding for a 172 amino acid residues protein with a conserved domain for the ferroxidase center characteristic for heavy chains of vertebrate ferritin. Prawn ferritin transcripts are expressed in muscle, heart, hepatopancreas, stomach, hemocytes, ovary and testis. Quantitative real-time PCR revealed that the abundance of ferritin transcript was highest in the hepatopancreas, followed by the testis. The expression of the ferritin transcript in the muscle significantly increased 6-fold at 3 h after injection of iron. In the ovary, a high expression of ferritin transcript was first detected with nearly a 4-fold increase after 3 h post-injection that remained elevated for 48 h. Heart ferritin mRNA expression increased up to 8-fold at 24 h. No significant difference was found in the hepatopancreas, hemocytes and testis. These results strongly suggested that the expression of prawn ferritin is regulated by iron at the transcriptional level as found in insects, and iron increased prawn ferritin transcripts in a tissue-specific manner.