Department of Entomology, Kansas State University, Manhattan, KS, 66506, USA.
Institute of Biology, Freie Universität Berlin, Berlin, 14195, Germany.
New Phytol. 2014 Feb;201(3):928-939. doi: 10.1111/nph.12581. Epub 2013 Nov 7.
Some plant-derived anti-herbivore defensive proteins are induced by insect feeding, resist digestion in the caterpillar gut and are eliminated in the frass. We have identified several maize proteins in fall armyworm (Spodoptera frugiperda) frass that potentially play a role in herbivore defense. Furthermore, the toxicity of one of these proteins, ribosome-inactivating protein 2 (RIP2), was assessed and factors regulating its accumulation were determined. To understand factors regulating RIP2 protein accumulation, maize (Zea mays) plants were infested with fall armyworm larvae or treated with exogenous hormones. The toxicity of recombinant RIP2 protein against fall armyworm was tested. The results show that RIP2 protein is synthesized as an inactive proenzyme that can be processed in the caterpillar gut. Also, caterpillar feeding, but not mechanical wounding, induced foliar RIP2 protein accumulation. Quantitative real-time PCR indicated that RIP2 transcripts were rapidly induced (1 h) and immunoblot analysis indicated that RIP2 protein accumulated soon after attack and was present in the leaf for up to 4 d after caterpillar removal. Several phytohormones, including methyl jasmonate, ethylene, and abscisic acid, regulated RIP2 protein expression. Furthermore, bioassays of purified recombinant RIP2 protein against fall armyworm significantly retarded caterpillar growth. We conclude that the toxic protein RIP2 is induced by caterpillar feeding and is one of a potential suite of proteins that defend maize against chewing herbivores.
一些植物源抗食草防御蛋白被昆虫取食诱导，抵抗毛虫肠道中的消化，并在粪便中被消除。我们已经在秋粘虫（Spodoptera frugiperda）粪便中鉴定出几种可能在草食性防御中发挥作用的玉米蛋白。此外，还评估了其中一种蛋白核糖体失活蛋白 2（RIP2）的毒性，并确定了调节其积累的因素。为了了解调节 RIP2 蛋白积累的因素，用秋粘虫幼虫或外源激素处理玉米（Zea mays）植株。测试了重组 RIP2 蛋白对秋粘虫的毒性。结果表明，RIP2 蛋白作为无活性的前酶合成，可以在毛虫肠道中进行加工。此外，毛虫取食而不是机械损伤诱导叶片 RIP2 蛋白积累。实时定量 PCR 表明 RIP2 转录物迅速诱导（1 小时），免疫印迹分析表明 RIP2 蛋白在取食后很快积累，并在取食后长达 4 天存在于叶片中。几种植物激素，包括茉莉酸甲酯、乙烯和脱落酸，调节 RIP2 蛋白的表达。此外，纯化的重组 RIP2 蛋白对秋粘虫的生物测定显著减缓了毛虫的生长。我们得出结论，有毒蛋白 RIP2 是由毛虫取食诱导的，是防御玉米咀嚼性食草动物的潜在蛋白之一。
