Department of Entomology, China Agricultural University, Beijing 100193, China.
Int J Biol Sci. 2011;7(6):848-68. doi: 10.7150/ijbs.7.848. Epub 2011 Jul 17.
The three-dimensional structures of two odorant binding proteins (OBPs) and one chemosensory protein (CSP) from a polyphagous ectoparasitoid Scleroderma guani (Hymenoptera: Bethylidae) were resolved bioinformatically. The results show that both SguaOBP1 and OBP2 are classic OBPs, whereas SguaCSP1 belongs to non-classic CSPs which are considered as the "Plus-C" CSP in this report. The structural differences between the two OBPs and between OBP and CSP are thoroughly described, and the structural and functional significance of the divergent C-terminal regions (e.g., the prolonged C-terminal region in SguaOBP2 and the additional pair of cysteines in SguaCSP1) are discussed. The immunoblot analyses with antisera raised against recombinant SguaOBP1, OBP2, and CSP1, respectively, indicate that two SguaOBPs are specific to antennae, whereas SguaCSP1, which are more abundant than OBPs and detected in both male and female wasps, expresses ubiquitously across different tissues.We also describe the ultrastructure of the antennal sensilla types in S. guani and compare them to 19 species of parasitic Hymenoptera. There are 11 types of sensilla in the flagellum and pedicel segments of antennae in both male and female wasps. Seven of them, including sensilla placodea (SP), long sensilla basiconica (LSB), sensilla coeloconica (SC), two types of double-walled wall pore sensilla (DWPS-I and DWPS-II), and two types of sensilla trichodea (ST-I and ST-II), are multiporous chemosensilla. The ultralsturctures of these sensilla are morphologically characterized. In comparison to monophagous specialists, the highly polyphagous generalist ectoparasitoids such as S. guani possess more diverse sensilla types which are likely related to their broad host ranges and complex life styles. Our immunocytochemistry study demonstrated that each of the seven sensilla immunoreacts with at least one antiserum against SguaOBP1, OBP2, and CSP1, respectively. Anti-OBP2 is specifically labeled in DWPS-II, whereas the anti-OBP1 shows a broad spectrum of immunoactivity toward four different sensilla (LSB, SP, ST-I and ST-II). On the other hand, anti-CSP1 is immunoactive toward SP, DWPS-I and SC. Interestingly, a cross co-localization pattern between SguaOBP1 and CSP1 is documented for the first time. Given that the numbers of OBPs and CSPs in many insect species greatly outnumber their antennal sensilla types, it is germane to suggest such phenomenon could be the rule rather than the exception.
从一种多食性外寄生蜂 Scleroderma guani（膜翅目：Bethylidae）中解析了两种气味结合蛋白（OBP）和一种化学感受蛋白（CSP）的三维结构。结果表明，SguaOBP1 和 OBP2 均为经典的 OBP，而 SguaCSP1 属于非经典的 CSP，在本报告中被认为是“Plus-C”CSP。详细描述了两个 OBP 之间以及 OBP 和 CSP 之间的结构差异，并讨论了发散的 C 末端区域（例如，SguaOBP2 中延长的 C 末端区域和 SguaCSP1 中额外的一对半胱氨酸）的结构和功能意义。用针对重组 SguaOBP1、OBP2 和 CSP1 分别产生的抗血清进行的免疫印迹分析表明，两个 SguaOBP 均特异性地位于触角上，而 CSP1 在雄蜂和雌蜂中均比 OBPs 更丰富，且在不同组织中均有表达。我们还描述了 S. guani 触角感觉器类型的超微结构，并将其与 19 种寄生膜翅目物种进行了比较。在雄蜂和雌蜂的触角鞭节和柄节中，有 11 种感觉器类型。其中 7 种为多微孔化学感觉器，包括鳞片状感觉器（SP）、长基锥形感觉器（LSB）、腔锥形感觉器（SC）、两种双壁壁孔感觉器（DWPS-I 和 DWPS-II）和两种毛形感觉器（ST-I 和 ST-II）。这些感觉器的超微结构在形态上进行了特征描述。与单食性专家相比，高度多食性的外寄生蜂，如 S. guani，具有更多样化的感觉器类型，这可能与其广泛的宿主范围和复杂的生活方式有关。我们的免疫细胞化学研究表明，七种感觉器中的每一种都至少与一种针对 SguaOBP1、OBP2 和 CSP1 的抗血清发生免疫反应。抗 OBP2 特异性标记 DWPS-II，而抗 OBP1 对四种不同感觉器（LSB、SP、ST-I 和 ST-II）具有广谱免疫活性。另一方面，抗 CSP1 对 SP、DWPS-I 和 SC 具有免疫活性。有趣的是，首次记录到 SguaOBP1 和 CSP1 之间的交叉共定位模式。鉴于许多昆虫物种中的 OBPs 和 CSPs 的数量远远超过其触角感觉器类型，因此可以假设这种现象很可能是普遍现象而不是例外。
