Insect Science Lab., Graduate School of Agricultural Science, Kobe University, Nada, Kobe, Japan.
Insect Mol Biol. 2010 Dec;19(6):787-98. doi: 10.1111/j.1365-2583.2010.01035.x.
The brown planthopper, Nilaparvata lugens, is a serious pest of rice crops throughout Asia and exhibits wing dimorphism, with brachypterous adults having reduced wings and macropterous adults possessing fully developed wings. To understand the reproductive strategies in two wing-morphs of this insect, the transcript encoding the major yolk protein precursor, vitellogenin (Vg), was cloned. The complete mRNA transcript was 6314 bp, which encodes a protein of 2063 residues including an 18-residue putative signal peptide. Analysis of the mature protein revealed two vitellogenin-N (or lipoprotein amino-terminal) domains near the N-terminus and a von Willebrand factor type D domain near the C-terminus. In addition, a highly conserved motif GL/ICG, and a number of cysteine residues were identified near the C-terminus. Northern blot analysis identified a ∼6.8 kb Vg gene transcript that was expressed exclusively in the adult female fat body cells. The expression profile revealed that the Vg gene starts to be expressed earlier (on day 3) in brachypters as compared to macropters where the mRNA transcript was observed on day 4. However, in both morphs, the amount of Vg mRNA increased to reach high levels during vitellogenic periods [from day 4 (in brachypters) and day 5 (in macropters) and onwards]. Reflecting the RNA transcription pattern, the Vg signal was detected by immunoblotting on day 3 and day 4 in haemolymph of brachypterous and macropterous females, respectively, and that was increased every day and remained high during the vitellogenic periods. Furthermore, the topical application of juvenile hormone (JH) III had up-regulated the Vg gene expression suggesting that the Vg gene is regulated by JH in N. lugens. In addition, it was demonstrated by Southern blot analysis that there exists a single copy of the gene in the N. lugens genome. A delayed trend in expression (of both the transcript and the protein) demonstrated by macropterous females in the present studies supports the hypothesis of prereproductive long distance migration in this wing-dimorphic species.
褐飞虱，Nilaparvata lugens，是亚洲水稻作物的严重害虫，表现出翅二型性，短翅成虫的翅膀发育不全，而长翅成虫的翅膀则完全发育。为了了解这种昆虫两个翅型的生殖策略，克隆了编码主要卵黄蛋白前体的转录本，卵黄蛋白原（Vg）。完整的 mRNA 转录本为 6314bp，编码 2063 个残基的蛋白质，包括 18 个残基的假定信号肽。对成熟蛋白的分析表明，在 N 端附近有两个卵黄蛋白-N（或脂蛋白氨基末端）结构域，在 C 端附近有一个 von Willebrand 因子 D 型结构域。此外，在 C 端附近还鉴定出一个高度保守的基序 GL/ICG 和一些半胱氨酸残基。Northern blot 分析鉴定出一个约 6.8kb 的 Vg 基因转录本，该转录本仅在成年雌性脂肪体细胞中表达。表达谱表明，Vg 基因在短翅个体中的表达开始较早（第 3 天），而在长翅个体中则在第 4 天观察到 mRNA 转录本。然而，在两种形态中，Vg mRNA 的数量都增加到了产卵管期的高水平[第 4 天（短翅）和第 5 天（长翅）及以后]。反映 RNA 转录模式，在短翅和长翅雌性的血液中分别在第 3 天和第 4 天检测到 Vg 信号，并且每天都增加，并在产卵管期保持高水平。此外，应用保幼激素（JH）III 处理可上调 Vg 基因的表达，表明 Vg 基因在褐飞虱中受 JH 调控。此外，Southern blot 分析表明，褐飞虱基因组中存在单个基因拷贝。本研究中长翅雌虫表达的延迟趋势（无论是转录本还是蛋白质）支持了这种翅二型物种存在预生殖远距离迁移的假说。
