The metabolic adaptations by which phloem-feeding insects counteract plant defense compounds are poorly known. Two-component plant defenses, such as glucosinolates, consist of a glucosylated protoxin that is activated by a glycoside hydrolase upon plant damage. Phloem-feeding herbivores are not generally believed to be negatively impacted by two-component defenses due to their slender piercing-sucking mouthparts, which minimize plant damage. However, here we document that glucosinolates are indeed activated during feeding by the whitefly Bemisia tabaci. This phloem feeder was also found to detoxify the majority of the glucosinolates it ingests by the stereoselective addition of glucose moieties, which prevents hydrolytic activation of these defense compounds. Glucosylation of glucosinolates in B. tabaci was accomplished via a transglucosidation mechanism, and two glycoside hydrolase family 13 (GH13) enzymes were shown to catalyze these reactions. This detoxification reaction was also found in a range of other phloem-feeding herbivores.

人们对韧皮部昆虫对抗植物防御化合物的代谢适应知之甚少。双组分植物防御，例如芥子油苷，由葡萄糖基化原毒素组成，在植物受损时由糖苷水解酶激活。一般认为，以韧皮部为食的食草动物不会受到两部分防御的负面影响，因为它们的口器细长，可最大限度地减少对植物的损害。然而，我们在这里记录了芥子油苷确实在烟粉虱取食过程中被激活。还发现这种韧皮部饲养层通过立体选择性添加葡萄糖部分来解毒其摄入的大部分芥子油苷，从而防止这些防御化合物的水解激活。烟粉虱中芥子油苷的葡萄糖基化是通过葡萄糖苷转移机制完成的，并且两种糖苷水解酶家族 13 (GH13) 酶被证明可以催化这些反应。在一系列其他以韧皮部为食的草食动物中也发现了这种解毒反应。