Impact of acute stress on antimicrobial polypeptides mRNA copy number in several tissues of marine sea bass (Dicentrarchus labrax)

We firstly isolated and deposited in Genbank database the cDNA sequences encoding for hemoglobin-β-like protein (Hb-LP) [GeneBank: JN410659], H2B histone-like protein 1 (HLP1) GenBank: JN410660], and HLP2 [GenBank: JN410661]. The "de novo" prediction of the three-dimensional structures for each protein is presented. Phylogenetic trees were constructed on Hb-LP, HLP1, and HLP2 sequences of sea bass and those of other teleost, avian, reptiles, amphibian and mammalian species. We then used real time RT-PCR technology to monitor for the first time in sea bass, dynamic changes in mRNA copy number of Hb-LP, HLP1, HLP2, and dicentracin in gills, skin, eyes, stomach and proximal intestine in response to acute crowding/confinement stress. We showed that acute crowding stress induces an increase in the expression levels of the aforementioned genes, in gills and skin of sea bass, but not in other tissues, and that this expression patterns are not always rapidly reversed upon re-exposure to normal conditions.The higher expression of the four target genes in gills and skin of sea bass suggests that this AMPP represents a first and immediate line of defense in combating pathogens and stressors since these tissues constitute the first physiological barriers of the animal.Antimicrobial polypeptides (AMPPs), consisting of small proteins with antimicrobial activity, are humoral components of the vertebrate and invertebrate innate immune system. In fish, the acquired immune response displays a poor immunological memory and slow lymphocyte proliferation [1,2] due to its evolutionary status [3] and poikilothermic nature. For this reason the innate immune system, which shows an instant and relatively temperature-independent response, is of primary importance in combating infections [4]. Several AMPPs have been isolated from fish, including commercially important species, such as misgurin in loach (Misgurnus anguillicaudatus) [5], epinecidin in grouper (Epinephelus coioides) [6], pleuroci