Department of Fisheries Science, Faculty of Agricultural Technology, King Mongkut's Institute of Technology, Ladkrabang, Bangkok 10520, Thailand.
Fish Shellfish Immunol. 2010 Sep;29(3):464-8. doi: 10.1016/j.fsi.2010.05.014. Epub 2010 May 24.
Melanization is an important component of the innate immune responses in invertebrates and it is essential for defense against invading microorganism. Melanin formation, which is a result of activation of the so called prophenoloxidase activating system, needs to be controlled due to the dangerous effects of quinones and melanin which are produced during the process of melanization. Here, a cDNA for a melanization inhibition protein (MIP), named PmMIP, was identified from the black tiger shrimp, Penaeus monodon by RT-PCR using degenerated oligonucleotide primers and RACE-PCR. The complete sequence significantly matched MIP of the freshwater crayfish Pacifastacus leniusculus (PlMIP). PmMIP contains an N-terminal signal peptide and a fibrinogen related domain (FReD). RT-PCR was applied to examine the expression profiles of PmMIP in various tissues of juvenile P. monodon. PmMIP was expressed in all examined tissues except hemocytes and at very low levels in hepatopancreas and ovaries. The expression of this gene was very low during the larval stages and hardly present in egg and at the nauplius stage. A time-course expression analysis of PmMIP upon Vibrio harveyi challenge at protein levels in plasma was determined. The result shows that MIP protein in plasma was induced at 6 h and disappeared at 12 and 24 h and then the protein reappeared at 48 and 72 h post injection. These results suggest that upon bacterial infection the PmMIP protein is first released from tissues into hemolymph and then degraded to allow melanization to occur for fighting against bacteria.
黑化是无脊椎动物先天免疫反应的一个重要组成部分，对于抵御入侵的微生物至关重要。黑色素的形成是所谓的酚氧化酶原激活系统激活的结果，由于在黑化过程中产生的醌和黑色素的危险作用，需要对其进行控制。在这里，通过使用简并寡核苷酸引物和 RACE-PCR，从黑虎虾 Penaeus monodon 通过 RT-PCR 鉴定了一种黑化抑制蛋白 (MIP) 的 cDNA，命名为 PmMIP。完整的序列与淡水小龙虾 Pacifastacus leniusculus 的 MIP（PlMIP）非常匹配。PmMIP 含有一个 N 端信号肽和一个纤维蛋白原相关结构域 (FReD)。RT-PCR 用于检测 P. monodon 幼体中 PmMIP 的各种组织中的表达谱。PmMIP 在除血细胞外的所有检查组织中均有表达，在肝胰腺和卵巢中表达水平非常低。该基因在幼虫阶段的表达水平非常低，在卵和无节幼体阶段几乎不存在。在蛋白水平上，通过对哈维弧菌(Vibrio harveyi)攻击后的血浆进行时间过程表达分析，确定了 PmMIP 的表达情况。结果表明，MIP 蛋白在血浆中于 6 小时被诱导，并在 12 和 24 小时消失，然后在注射后 48 和 72 小时再次出现。这些结果表明，在细菌感染后，PmMIP 蛋白首先从组织释放到血液中，然后降解，以使黑化发生以对抗细菌。
