Chiriboga M Xavier, Guo Huijuan, Campos-Herrera Raquel, Röder Gregory, Imperiali Nicola, Keel Christoph, Maurhofer Monika, Turlings Ted C J
Fundamental and Applied Research in Chemical Ecology (FARCE Lab), Institute of Biology, University of Neuchâtel, Emile-Argand 11, 2000, Neuchâtel, Switzerland.
State Key Laboratory of Integrated Management of Insect Pests and Rodents, Institute of Zoology, Chinese Academy of Sciences, Beijin, 100101, China.
Oecologia. 2018 Jun;187(2):459-468. doi: 10.1007/s00442-017-4055-5. Epub 2018 Feb 9.
When larvae of rootworms feed on maize roots they induce the emission of the sesquiterpene (E)-β-caryophyllene (EβC). EβC is attractive to entomopathogenic nematodes, which parasitize and rapidly kill the larvae, thereby protecting the roots from further damage. Certain root-colonizing bacteria of the genus Pseudomonas also benefit plants by promoting growth, suppressing pathogens or inducing systemic resistance (ISR), and some strains also have insecticidal activity. It remains unknown how these bacteria influence the emissions of root volatiles. In this study, we evaluated how colonization by the growth-promoting and insecticidal bacteria Pseudomonas protegens CHA0 and Pseudomonas chlororaphis PCL1391 affects the production of EβC upon feeding by larvae of the banded cucumber beetle, Diabrotica balteata Le Conte (Coleoptera: Chrysomelidae). Using chemical analysis and gene expression measurements, we found that EβC production and the expression of the EβC synthase gene (tps23) were enhanced in Pseudomonas protegens CHA0-colonized roots after 72 h of D. balteata feeding. Undamaged roots colonized by Pseudomonas spp. showed no measurable increase in EβC production, but a slight increase in tps23 expression. Pseudomonas colonization did not affect root biomass, but larvae that fed on roots colonized by P. protegens CHA0 tended to gain more weight than larvae that fed on roots colonized by P. chlororaphis PCL1391. Larvae mortality on Pseudomonas spp. colonized roots was slightly, but not significantly higher than on non-colonized control roots. The observed enhanced production of EβC upon Pseudomonas protegens CHA0 colonization may enhance the roots' attractiveness to entomopathogenic nematodes, but this remains to be tested.
当根虫幼虫取食玉米根时，它们会诱导倍半萜（E）-β-石竹烯（EβC）的释放。EβC对昆虫病原线虫具有吸引力，这些线虫会寄生并迅速杀死幼虫，从而保护根部免受进一步损害。某些假单胞菌属的根部定殖细菌也通过促进生长、抑制病原体或诱导系统抗性（ISR）使植物受益，并且一些菌株还具有杀虫活性。这些细菌如何影响根挥发物的释放仍不清楚。在本研究中，我们评估了促生长和杀虫细菌绿针假单胞菌CHA0和嗜氯假单胞菌PCL1391的定殖如何影响带纹黄瓜甲虫（Diabrotica balteata Le Conte，鞘翅目：叶甲科）幼虫取食时EβC的产生。通过化学分析和基因表达测量，我们发现，在带纹黄瓜甲虫取食72小时后，定殖有绿针假单胞菌CHA0的根中EβC的产生和EβC合酶基因（tps23）的表达增强。定殖有假单胞菌属细菌的未受损根中，EβC的产生没有可测量的增加，但tps23的表达略有增加。假单胞菌定殖不影响根生物量，但取食定殖有绿针假单胞菌CHA0的根的幼虫比取食定殖有嗜氯假单胞菌PCL1391的根的幼虫往往体重增加更多。在定殖有假单胞菌属细菌的根上，幼虫死亡率略高于未定殖的对照根，但差异不显著。观察到定殖绿针假单胞菌CHA0后EβC产生增强，这可能会增强根对昆虫病原线虫的吸引力，但这仍有待测试。
