Müller Caroline, Wittstock Ute
Julius-von-Sachs-Institut für Biowissenschaften, Universität Würzburg, Julius-von-Sachs-Platz 3, D-97082 Würzburg, Germany.
Insect Biochem Mol Biol. 2005 Oct;35(10):1189-98. doi: 10.1016/j.ibmb.2005.06.001.
Larvae of the sawfly Athalia rosae sequester glucosinolates from their various host plants of the Brassicaceae into their hemolymph for defensive purposes. We found that the glucosinolate concentration in the insect varies in a fluctuating manner during larval development. Analyses of larvae which had been offered diets with different glucosinolate profiles showed that there is an equilibrium between a rapid uptake of glucosinolates into the hemolymph and a continuous turn-over. Injection of glucotropaeolin into the hemolymph and ingestion of the same amount resulted in similar levels of intact glucosinolates recovered from larvae after different periods of time. This indicates that hemolymph glucosinolates are the principal source for glucosinolate degradation. Feeding experiments with [14C]-labeled glucotropaeolin revealed that the majority of the ingested glucosinolate is excreted as one or more unidentified metabolite(s) within 14 h. We found no indication for the presence of an insect myrosinase, or sulfatase in A. rosae, which have been shown to be involved in glucosinolate metabolism in other specialists feeding on Brassicaceae. Furthermore, the metabolism of sinalbin in A. rosae seems to result in different products than its metabolism in the caterpillar Pieris rapae. Obviously, A. rosae has yet another way of coping with the glucosinolates.
叶蜂Athalia rosae的幼虫会将十字花科各种寄主植物中的芥子油苷隔离到血淋巴中用于防御。我们发现，在幼虫发育过程中，昆虫体内的芥子油苷浓度呈波动变化。对喂食不同芥子油苷谱饲料的幼虫进行分析表明，芥子油苷快速吸收进入血淋巴和持续周转之间存在平衡。向血淋巴中注射葡萄糖芥苷并摄入相同量的葡萄糖芥苷，在不同时间段后，从幼虫中回收的完整芥子油苷水平相似。这表明血淋巴中的芥子油苷是芥子油苷降解的主要来源。用[14C]标记的葡萄糖芥苷进行的喂养实验表明，大部分摄入的芥子油苷在14小时内作为一种或多种未鉴定的代谢物排出。我们没有发现A. rosae中存在昆虫黑芥子酶或硫酸酯酶的迹象，而在以十字花科为食的其他专食性昆虫中，这些酶已被证明参与芥子油苷代谢。此外，A. rosae中芥子碱的代谢产物似乎与菜青虫Pieris rapae中的代谢产物不同。显然，A. rosae有另一种应对芥子油苷的方式。
