SGER: Role of Cytochrome P450 in Chemosensory Mediation of Oviposition in Papilio polyxenes

SGER：细胞色素P450在多种凤蝶产卵的化学感官调节中的作用伊利诺伊大学香槟分校的May Berenbaum了解植物食性昆虫，如鳞翅目、蝴蝶和飞蛾，如何识别和利用它们赖以生存的植物，是理解这一物种异常丰富的生物群多样性的关键。无法确定寄主植物如何被识别和处理的特定基因一直是一个主要障碍；尽管基因组计划提供了巨大的清单，但为影响行为和生理的基因分配功能仍然是一个挑战，而且大多数模式生物的生态学特征是大量的知识空白，如遗传学上著名的“果蝇”--黑腹果蝇。调节植物与昆虫相互作用的关键基因是细胞色素P450单加氧酶，这种酶不仅负责为食叶毛虫消耗的杀虫植物化合物解毒，而且还负责分解雌性蝴蝶的触角和腿所检测到的植物气味，这些雌性蝴蝶正在寻找产卵的植物。黑燕尾乳突多酚提供了一个非同寻常的机会来表征单个物种中影响毛虫对寄主植物的利用和雌性蝴蝶对寄主植物识别的P450。它的化学生态具有独特的特征，产卵的刺激剂以及影响毛虫生长的有毒化学物质都是已知的。此外，对于非模式物种，其分子生物学异常完善，毛虫肠道中的P450酶CYP6B1和CYP6B3有助于对寄主植物中的杀虫化合物进行解毒，而CYP4G28则是雌性蝴蝶腿部的特征，可能参与雌性蝴蝶识别寄主植物。因此，这一SGER的目标是通过以下方式确定CYP4G28的功能：1.确定该基因是否在雌性蝴蝶产卵前用于“品尝”和识别寄主植物的感觉结构中特异性表达(使用免疫定位和原位杂交技术)；2.分子建模，以确定已知的刺激产卵的化学物质是否“适合”到CYP4G28蛋白的活性部位；3.进行行为生物测试，以确定抑制蝴蝶前腿中的P450是否会阻止雌性蝴蝶识别它们的寄主植物。拟议活动产生的更广泛影响包括包含植物化学、分子生物学和昆虫学元素的跨学科培训；学生将接受对21世纪的竞争力至关重要的基础广泛的培训。研究结果将发表在科学期刊、整合分子生物学和化学生态学的教科书、流行著作和公开讲座上。在对整个社会的其他潜在好处中，将是更好地理解细胞染色体P450的进化过程。这些酶有助于发展杀虫剂抗性和获得新的寄主植物，包括农作物，这一现象具有巨大的生态和经济意义。

SGER: Role of cytochrome P450 in chemosensory mediation of oviposition in Papilio polyxenesMay Berenbaum, University of Illinois at Urbana-ChampaignUnderstanding how plant-feeding insects such as the Lepidoptera, the butterflies and moths, recognize and utilize the plants on which they feed is key to understanding the diversification of this exceptionally species-rich group of organisms. The inability to identify specific genes underlying how hostplants are identified and processed has been a major obstacle; although genome projects provide enormous inventories the challenge remains to assign function to genes affecting behavior and physiology and substantial knowledge gaps characterize the ecology of most model organisms such as Drosophila melanogaster, the "fruit fly" of genetics fame. Key genes mediating plant-insect interactions are the cytochrome P450 monooxygenases, enzymes responsible not only for detoxifying insecticidal plant compounds consumed by leaf-feeding caterpillars but also breaking down plant odorants detected by the antennae and legs of female butterflies searching for plants on which to lay eggs . An extraordinary opportunity for characterizing P450s within a single species that influence hostplant use by caterpillars and hostplant recognition by female butterflies is presented by the black swallowtail Papilio polyxenes. Its chemical ecology is uniquely well-characterized, stimulants for egg-laying as well as toxic chemicals that affect caterpillar growth are known. As well, for a non-model species, its molecular biology is unusually well-documented, with P450 enzymes CYP6B1 and CYP6B3 in caterpillar guts contributing to detoxification of insecticidal compounds in hostplants, and CYP4G28 characterized from the legs of female butterflies possibly involved in hostplant recognition by female butterflies. Thus, the objectives of this SGER are to determine CYP4G28 function by 1. determining whether this gene is expressed specifically in the sensory structures used by female butterflies for "tasting" and recognizing their hostplants prior to laying eggs (using the techniques of immunolocalization and in situ hybridization); 2. molecular modeling to determine whether chemicals known to stimulate egg-laying "fit" into the active site of the CYP4G28 protein; 3. conducting behavioral bioassays to determine if inhibiting the P450s in butterfly forelegs prohibits female butterflies from recognizing their hostplants. Broader impacts resulting from the proposed activities include interdisciplinary training encompassing elements of phytochemistry, molecular biology, and entomology; students will receive broad-based training essential for competitiveness in the 21st century. Findings will be published in scientific journals, in a textbook integrating molecular biology and chemical ecology, and in popular writings and public lectures. Among other potential benefits to society at large will be a greater understanding of the process by which cytochome P450s evolve. These enzymes contribute to the development of insecticide resistance and the acquisition of new hostplants, including crops, phenomena of tremendous ecological and economic importance.