Shiojiri Kaori, Ozawa Rika, Matsui Kenji, Kishimoto Kyutaro, Kugimiya Soichi, Takabayashi Junji
Center for Ecological Research, Kyoto University, Otsu 520-2113, Japan.
J Chem Ecol. 2006 May;32(5):969-79. doi: 10.1007/s10886-006-9047-6. Epub 2006 May 20.
To elucidate the role of the plant lipoxygenase (LOX)/lyase pathway for host search behavior of two parasitic wasps attacking herbivorous larvae, an Arabidopsis mutant (all84) was isolated with a mutation somewhere in the LOX/lyase pathway. Detached leaves of the mutant were shown to release less (Z)-3-hexenal, a first green leaf volatile (GLV) product of the LOX/lyase pathway. The braconid larval parasitoids studied, Cotesia glomerata and Cotesia plutella, differ in their ability to discriminate among plant volatiles induced by feeding of lepidopteran hosts and nonhosts: C. plutella only responds to plant volatiles induced by hosts (Plutella larvae), whereas the response by the more generalist C. glomerata is not host specific. The Arabidopsis mutant all84 infested by Pieris larvae was less attractive to C. glomerata than Arabidopsis wild type (wt) infested by the host larvae. C. glomerata was attracted by two of the GLV biosynthesized through the LOX/lyase pathway, (E)-2-hexenal and (Z)-3-hexenyl acetate. However, attraction of C. plutellae to volatiles from Plutella-infested all84 plants did not differ from attraction to host-infested wt Arabidopsis. Both wasp species were arrested to the respective host-infested edge of the wt leaf by showing characteristic antennal searching behavior on the edge. In C. glomerata, the duration of this searching behavior at the infested leaf edge was significantly shorter on all84 plants than on wt plants. By contrast, the duration of the searching behavior of C. plutellae on the host-infested leaf edge of all84 was not significantly different from that on the wt leaf. These data suggest that the LOX/lyase pathway is directly involved in the production of attractants and arrestants important for host search behavior of the more generalist C. glomerata, but not for the specialist C. plutellae.
为了阐明植物脂氧合酶（LOX）/裂解酶途径在两种攻击草食性幼虫的寄生蜂寻找宿主行为中的作用，分离出了一种拟南芥突变体（all84），其在LOX/裂解酶途径的某个位置发生了突变。研究发现，该突变体的离体叶片释放的（Z）-3-己烯醛较少，（Z）-3-己烯醛是LOX/裂解酶途径产生的第一种绿叶挥发物（GLV）产物。所研究的茧蜂幼虫寄生蜂，即菜蛾盘绒茧蜂和小菜蛾盘绒茧蜂，在区分由鳞翅目宿主和非宿主取食诱导的植物挥发物的能力上存在差异：小菜蛾盘绒茧蜂仅对由宿主（小菜蛾幼虫）诱导的植物挥发物有反应，而更具广谱性的菜蛾盘绒茧蜂的反应则不具有宿主特异性。与被宿主幼虫侵染的拟南芥野生型（wt）相比，被粉蝶幼虫侵染的拟南芥突变体all84对菜蛾盘绒茧蜂的吸引力较小。菜蛾盘绒茧蜂会被通过LOX/裂解酶途径生物合成的两种GLV，即（E）-2-己烯醛和（Z）-3-己烯基乙酸酯所吸引。然而，小菜蛾盘绒茧蜂对被小菜蛾侵染的all84植物挥发物的吸引力与对被宿主侵染的野生型拟南芥的吸引力没有差异。两种黄蜂都会通过在wt叶片被各自宿主侵染的边缘表现出特征性的触角搜索行为而停留在该边缘。在菜蛾盘绒茧蜂中，在all84植物上，这种在被侵染叶片边缘的搜索行为持续时间明显短于在wt植物上。相比之下，小菜蛾盘绒茧蜂在all84被宿主侵染的叶片边缘的搜索行为持续时间与在wt叶片上的没有显著差异。这些数据表明，LOX/裂解酶途径直接参与了对更具广谱性的菜蛾盘绒茧蜂寻找宿主行为重要的引诱剂和滞留剂的产生，但对专一性的小菜蛾盘绒茧蜂则并非如此。
