Host plant species determines symbiotic bacterial community mediating suppression of plant defenses

Authors: CHUNG, SEUNG - Cornell University; Scully, Erin; PEIFFER, MICHELLE - Pennsylvania State University; Geib, Scott; ROSA, CRISTINA - Pennsylvania State University; HOOVER, KELLI - Pennsylvania State University; FELTON, GARY - Pennsylvania State University

Submitted to: Scientific Reports
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/25/2016
Publication Date: 1/3/2017
Citation: Chung, S.H., Scully, E.D., Peiffer, M., Geib, S.M., Rosa, C., Hoover, K., Felton, G.W. 2017. Host plant species determines symbiotic bacterial community mediating suppression of plant defenses. Scientific Reports. 7:39690. doi:10.1038/srep39690.

Interpretive Summary: Symbiotic bacteria associated with insects play important roles in plant-insect interactions. For example, Colorado potato beetles (CBP), which feed on several plants in the genus Solanum (e.g., tomatoes and potatoes), deposit bacteria in oral secretions onto plants during feeding, which have been previously shown to suppress defense responses of tomatoes. However, it is not known if these bacteria can suppress the defenses of CPB's other wild and domesticated host plants. We determined that CPB feeding on different plants, including tomato, potato, horsenettle, buffalobur, nightshade, and eggplant, deposited bacteria that was able to suppressed plant defense responses to some extent in all plants tested, but the degree to which defenses were suppressed varied among plant species. In addition, feeding on the six different hosts changed the composition of the gut community, including the relative abundance of three defense-suppressing bacteria, which were classified to the genera Pseudomonas, Enterobacter, and Stenotrophomonas. These results demonstrate that host plants can impact the bacterial community of CPB and its ability to manipulate plant defenses. In addition, the ability of the gut bacterial community to suppress defenses of several different plant species suggests that these bacteria may have facilitated host range expansion of CPB. Finally, these data provide insights to the mechanisms CPB uses to successfully colonize its hosts, which will ultimately lead to improved management strategies, potentially by targeting bacterial symbionts involved in suppressing plant defenses.

Technical Abstract: Herbivore associated bacteria are vital mediators of plant and insect interactions. Host plants play an important role in shaping the gut bacterial community of insects. Colorado potato beetles (CPB; Leptinotarsa decemlineata) use several Solanum plants as hosts in their natural environment. We previously showed that symbiotic gut bacteria from CPB larvae suppressed jasmonate (JA)-induced defenses in tomato. However, little is known about how changes in the bacterial community may be involved in the manipulation of induced defenses in wild and cultivated Solanum plants of CPB. Here, we examined suppression of JA-mediated defense in wild and cultivated hosts of CPB by chemical elicitors and their symbiotic bacteria. In addition, we investigated associations between the gut bacterial community and suppression of plant defenses using 16S rRNA amplicon sequencing. Symbiotic bacteria decreased plant defenses in all Solanum hosts and there were different gut bacterial communities in CPB fed on different host plants. When larvae were reared on different hosts, defense suppression differed among host plants. These results demonstrate that host plants influence herbivore gut bacterial communities and consequently affect the herbivore’s ability to manipulate JA-mediated plant defenses. Thus, the presence of symbiotic bacteria that suppress plant defenses might be involved in helping CPB adapt to wild and cultivated host plants.