Ament Kai, Kant Merijn R, Sabelis Maurice W, Haring Michel A, Schuurink Robert C
Swammerdam Institute for Life Sciences, Department of Plant Physiology, University of Amsterdam, 1098 SM Amsterdam, The Netherlands.
Plant Physiol. 2004 Aug;135(4):2025-37. doi: 10.1104/pp.104.048694. Epub 2004 Aug 13.
The tomato (Lycopersicon esculentum) mutant def-1, which is deficient in induced jasmonic acid (JA) accumulation upon wounding or herbivory, was used to study the role of JA in the direct and indirect defense responses to phytophagous mites (Tetranychus urticae). In contrast to earlier reports, spider mites laid as many eggs and caused as much damage on def-1 as on wild-type plants, even though def-1 lacked induction of proteinase inhibitor activity. However, the hatching-rate of eggs on def-1 was significantly higher, suggesting that JA-dependent direct defenses enhanced egg mortality or increased the time needed for embryonic development. As to gene expression, def-1 had lower levels of JA-related transcripts but higher levels of salicylic acid (SA) related transcripts after 1 d of spider mite infestation. Furthermore, the indirect defense response was absent in def-1, since the five typical spider mite-induced tomato-volatiles (methyl salicylate [MeSA], 4,8,12-trimethyltrideca-1,3,7,11-tetraene [TMTT], linalool, trans-nerolidol, and trans-beta-ocimene) were not induced and the predatory mite Phytoseiulus persimilis did not discriminate between infested and uninfested def-1 tomatoes as it did with wild-type tomatoes. Similarly, the expression of the MeSA biosynthetic gene salicylic acid methyltransferase (SAMT) was induced by spider mites in wild type but not in def-1. Exogenous application of JA to def-1 induced the accumulation of SAMT and putative geranylgeranyl diphosphate synthase transcripts and restored MeSA- and TMTT-emission upon herbivory. JA is therefore necessary to induce the enzymatic conversion of SA into MeSA. We conclude that JA is essential for establishing the spider mite-induced indirect defense response in tomato.
番茄（Lycopersicon esculentum）突变体def-1在受伤或遭受食草动物侵害时诱导茉莉酸（JA）积累存在缺陷，被用于研究JA在对植食性螨类（二斑叶螨Tetranychus urticae）的直接和间接防御反应中的作用。与早期报道不同，尽管def-1缺乏蛋白酶抑制剂活性的诱导，但叶螨在def-1上产的卵数量与在野生型植物上一样多，造成的损害也一样大。然而，def-1上卵的孵化率显著更高，这表明依赖JA的直接防御增强了卵的死亡率或增加了胚胎发育所需的时间。至于基因表达，在叶螨侵染1天后，def-1中JA相关转录本水平较低，但水杨酸（SA）相关转录本水平较高。此外，def-1中不存在间接防御反应，因为五种典型的叶螨诱导的番茄挥发物（水杨酸甲酯[MeSA]、4,8,12-三甲基十三碳-1,3,7,11-四烯[TMTT]、芳樟醇、反式橙花叔醇和顺式-β-罗勒烯）未被诱导，捕食螨智利小植绥螨（Phytoseiulus persimilis）在侵染和未侵染的def-1番茄之间没有像在野生型番茄之间那样表现出偏好。同样，MeSA生物合成基因水杨酸甲基转移酶（SAMT）的表达在野生型中被叶螨诱导，但在def-1中未被诱导。向def-1外源施用JA诱导了SAMT和假定的香叶基香叶基二磷酸合酶转录本的积累，并在食草动物侵害后恢复了MeSA和TMTT的释放。因此，JA是诱导SA酶促转化为MeSA所必需的。我们得出结论，JA对于建立番茄中叶螨诱导的间接防御反应至关重要。
