Bouvaine Sophie, Faure Marie-Line, Grebenok Robert J, Behmer Spencer T, Douglas Angela E
Department of Entomology, Cornell University, Ithaca, New York, United States of America.
Department of Biology, Canisius College, Buffalo, New York, United States of America.
PLoS One. 2014 Jan 20;9(1):e86256. doi: 10.1371/journal.pone.0086256. eCollection 2014.
The aphid Myzus persicae displays high mortality on tobacco plants bearing a transgene which results in the accumulation of the ketosteroids cholestan-3-one and cholest-4-en-3-one in the phloem sap. To test whether the ketosteroids are the basis of the plant resistance to the aphids, M. persicae were reared on chemically-defined diets with different steroid contents at 0.1-10 µg ml(-1). Relative to sterol-free diet and dietary supplements of the two ketosteroids and two phytosterols, dietary cholesterol significantly extended aphid lifespan and increased fecundity at one or more dietary concentrations tested. Median lifespan was 50% lower on the diet supplemented with cholest-4-en-3-one than on the cholesterol-supplemented diet. Aphid feeding rate did not vary significantly across the treatments, indicative of no anti-feedant effect of any sterol/steroid. Aphids reared on diets containing equal amounts of cholesterol and cholest-4-en-3-one showed fecundity equivalent to aphids on diets containing only cholesterol. Aphids were reared on diets that reproduced the relative steroid abundance in the phloem sap of the control and modified tobacco plants, and their performance on the two diet formulations was broadly equivalent. We conclude that, at the concentrations tested, plant ketosteroids support weaker aphid performance than cholesterol, but do not cause acute toxicity to the aphids. In plants, the ketosteroids may act synergistically with plant factors absent from artificial diets but are unlikely to be solely responsible for resistance of modified tobacco plants.
桃蚜在携带转基因的烟草植株上死亡率很高，该转基因导致韧皮部汁液中甾酮胆甾烷 - 3 - 酮和胆甾 - 4 - 烯 - 3 - 酮积累。为了测试甾酮是否是植物对蚜虫抗性的基础，将桃蚜饲养在化学定义的、含有0.1 - 10 µg ml⁻¹不同甾醇含量的饲料上。相对于无甾醇饲料以及两种甾酮和两种植物甾醇的饲料补充剂，在一种或多种测试的饲料浓度下，饲料中的胆固醇显著延长了蚜虫寿命并提高了繁殖力。补充胆甾 - 4 - 烯 - 3 - 酮的饲料上的蚜虫平均寿命比补充胆固醇的饲料上低50%。蚜虫的取食率在各处理之间没有显著差异，表明任何甾醇/甾酮都没有拒食作用。在含有等量胆固醇和胆甾 - 4 - 烯 - 3 - 酮的饲料上饲养的蚜虫繁殖力与仅含胆固醇饲料上的蚜虫相当。将蚜虫饲养在能再现对照烟草植株和转基因烟草植株韧皮部汁液中相对甾酮丰度的饲料上，它们在两种饲料配方上的表现大致相同。我们得出结论，在所测试的浓度下，植物甾酮比胆固醇对蚜虫生长的支持作用更弱，但不会对蚜虫造成急性毒性。在植物中，甾酮可能与人工饲料中不存在的植物因子协同作用，但不太可能是转基因烟草植株抗性的唯一原因。
