Tiu Shirley H K, Hui Jerome H L, He Jian-Guo, Tobe Stephen S, Chan Siu-Ming
Department of Zoology, The University of Hong Kong, Pokfulam, Hong Kong.
Mol Reprod Dev. 2006 Apr;73(4):424-36. doi: 10.1002/mrd.20433.
During gonad maturation, female shrimp accumulate the major egg yolk protein vitellin (Vn) in premolt stage, and the process of molting and reproduction is synchronized. Using a polyclonal anti-Vn antibody, immunopositive signals could be detected in the ovary and among the proteins secreted by the hepatopancreas by Western blot. In the ovary, Vn immunoreactivity was located in the posterior lobe. Hepatopancreas proteins with sizes identical to ovary vitellogenin (Vg) subunits (i.e., 78 and 157 kDa) were immunoreactive to the Vn antibody and these proteins included amino acid sequences identical to parts of the MeVg1 precursor. A major 7.8 kb MeVg1 transcript, was detected in the ovary. In the hepatopancreas, the transcripts were primarily small (<2.3 kb) and while the 7.8 kb transcript which constitutes <50% of the total Vg mRNA. MeVg1 transcript could be detected in the hepatopancreas of juvenile females with a maximum level during late intermolt and early premolt. To study the effect of different hormones on expression of MeVg1, explant cultures of hepatopancreas and ovary were developed. Although several hormones (20-hydroxyecdysone, estradiol (ES), farnesoic acid (FA), juvenile hormone (JH) III, methyl farnesoate, and progesterone (PG)) apparently stimulated MeVg1 gene expression, only FA consistently stimulated MeVg1 expression by the hepatopancreas explants, while both FA and 20-hydroxyecdysone were stimulated ovarian explants. In summary, (i) Vg transcripts can be detected in both reproductive and nonreproductive females; (ii) the presence of large quantities of smaller Vg transcripts and the absence of a large Vg precursor from the hepatopancreas suggests that smaller MeVg1 transcripts provide an important contribution to Vg synthesis in shrimp. Our results suggest that there is differential processing of the MeVg1 precursor in the ovary and hepatopancreas of shrimp.
在性腺成熟过程中，雌虾在蜕皮前阶段积累主要的卵黄蛋白卵黄磷蛋白（Vn），蜕皮和繁殖过程是同步的。使用多克隆抗Vn抗体，通过蛋白质免疫印迹法可在卵巢以及肝胰腺分泌的蛋白质中检测到免疫阳性信号。在卵巢中，Vn免疫反应性位于后叶。肝胰腺中大小与卵巢卵黄原蛋白（Vg）亚基相同（即78和157 kDa）的蛋白质对Vn抗体具有免疫反应性，这些蛋白质包含与MeVg1前体部分相同的氨基酸序列。在卵巢中检测到一个主要的7.8 kb MeVg1转录本。在肝胰腺中，转录本主要较小（<2.3 kb），而构成总Vg mRNA不到50%的7.8 kb转录本。在幼年雌虾的肝胰腺中可检测到MeVg1转录本，在蜕皮后期和蜕皮前期达到最高水平。为了研究不同激素对MeVg1表达的影响，建立了肝胰腺和卵巢的外植体培养。尽管几种激素（20-羟基蜕皮酮、雌二醇（ES）、法尼酸（FA）、保幼激素（JH）III、甲基法尼酯和孕酮（PG））明显刺激MeVg1基因表达，但只有FA持续刺激肝胰腺外植体的MeVg1表达，而FA和20-羟基蜕皮酮均刺激卵巢外植体。总之，（i）在生殖和非生殖雌虾中均可检测到Vg转录本；（ii）肝胰腺中存在大量较小的Vg转录本且不存在大的Vg前体，这表明较小的MeVg1转录本对虾的Vg合成有重要贡献。我们的结果表明，虾的卵巢和肝胰腺中MeVg1前体存在差异加工。
