Helicoverpa zea gut-associated bacteria indirectly induce defenses in tomato by triggering a salivary elicitor(s).
Insect gut-associated microbes modulating plant defenses have been observed in beetles and piercing-sucking insects, but the role of caterpillar-associated bacteria in regulating plant induced defenses has not been adequately examined. We identified bacteria from the regurgitant of field-collected Helicoverpa zea larvae using 16S ribosomal RNA (rRNA) gene sequencing and matrix-assisted laser desorption/ionization time of flight (MALDI-TOF) mass spectrometry. A combination of biochemical, molecular, and confocal electron microscopy methods were used to determine the role of caterpillar-associated bacteria in mediating defenses in Solanum lycopersicum (tomato). Laboratory-reared H. zea inoculated with one of the bacteria identified in field-collected H. zea, Enterobacter ludwigii, induced expression of the tomato defense-related enzyme polyphenol oxidase and genes regulated by jasmonic acid (JA), whereas the salicylic acid (SA)-responsive pathogenesis-related gene was suppressed. Additionally, saliva and its main component glucose oxidase from inoculated caterpillars played an important role in elevating tomato anti-herbivore defenses. However, there were only low detectable amounts of regurgitant or bacteria on H. zea-damaged tomato leaves. Our results suggest that H. zea gut-associated bacteria indirectly mediate plant-insect interactions by triggering salivary elicitors. These findings provide a proof of concept that introducing gut bacteria to a herbivore may provide a novel approach to pest management through indirect induction of plant resistance.
College of Crop Science, Fujian Agriculture and Forestry University, Fuzhou, Fujian, 350002, China.|Department of Entomology, Pennsylvania State University, University Park, PA, 16802, USA.|College of Natural Resources and Environment, South China Agricultural University, Guangzhou, Guangdong, 510640, China.
Jie
J
Wang
Department of Entomology, Pennsylvania State University, University Park, PA, 16802, USA.
Michelle
M
Peiffer
Department of Entomology, Pennsylvania State University, University Park, PA, 16802, USA.
Kelli
K
Hoover
Department of Plant Pathology and Environmental Microbiology, Pennsylvania State University, University Park, PA, 16802, USA.
Cristina
C
Rosa
College of Crop Science, Fujian Agriculture and Forestry University, Fuzhou, Fujian, 350002, China.|College of Natural Resources and Environment, South China Agricultural University, Guangzhou, Guangdong, 510640, China.
Rensen
R
Zeng
Department of Entomology, Pennsylvania State University, University Park, PA, 16802, USA.
Gary W
GW
Felton
D000818:Animals; D004156:Catechol Oxidase / Q000378:metabolism; D003517:Cyclopentanes; D004064:Digestive System / Q000382:microbiology*; D004754:Enterobacter / Q000502:physiology*; D005949:Glucose Oxidase / Q000378:metabolism; D060434:Herbivory; D007814:Larva / Q000382:microbiology; D007915:Lepidoptera / Q000382:microbiology*; D018551:Solanum lycopersicum / Q000201:enzymology / Q000276:immunology*; D054883:Oxylipins; D012463:Saliva / Q000378:metabolism*
D003517:Cyclopentanes; D054883:Oxylipins; C011006:jasmonic acid; D005949:Glucose Oxidase; D004156:Catechol Oxidase

Helicoverpa zea
; Solanum lycopersicum (tomato); glucose oxidase (GOX); induced defense; regurgitant; saliva; symbiotic bacteria