Anthropogenic increase in carbon dioxide compromises plant defense against invasive insects

Abstract

Elevated levels of atmospheric carbon dioxide (CO 2 ), a consequence of anthropogenic global change, can profoundly affect the interactions between crop plants and insect pests and may promote yet another form of global change: the rapid establishment of invasive species. Elevated CO 2 increased the susceptibility of soybean plants grown under field conditions to the invasive Japanese beetle ( Popillia japonica ) and to a variant of western corn rootworm ( Diabrotica virgifera virgifera ) resistant to crop rotation by down-regulating gene expression related to defense signaling [lipoxygenase 7 ( lox7 ), lipoxygenase 8 ( lox8 ), and 1-aminocyclopropane-1-carboxylate synthase ( acc-s )]. The down-regulation of these genes, in turn, reduced the production of cysteine proteinase inhibitors (CystPIs), which are specific deterrents to coleopteran herbivores. Beetle herbivory increased CystPI activity to a greater degree in plants grown under ambient than under elevated CO 2 . Gut cysteine proteinase activity was higher in beetles consuming foliage of soybeans grown under elevated CO 2 than in beetles consuming soybeans grown in ambient CO 2 , consistent with enhanced growth and development of these beetles on plants grown in elevated CO 2 . These findings suggest that predicted increases in soybean productivity under projected elevated CO 2 levels may be reduced by increased susceptibility to invasive crop pests.

Predicting the future of forests in the Mediterranean under climate change, with niche- and process-based models: CO2 matters!

“…Few interspecies comparisons exist, though the general tendencies have been shown to be conserved over a large number of species . It should be noted, however, that there is broad agreement that the effects of elevated CO 2 measured in experimental settings lacking potentially limiting influence of pests, weeds, nutrients, competition for resources, soil water, and air quality, may overestimate field responses of terrestrial vegetation (Long et al, 2006;Easterling et al, 2007;Tubiello et al, 2007;Ainsworth et al, 2008;Zavala et al, 2008).…”

Will Elevated Carbon Dioxide Concentration Amplify the Benefits of Nitrogen Fixation in Legumes?

“…However, additional folivory at elevated [CO 2 ] was reported in soybean, and the response was linked to increased sugar content and a compromised defense system. This indicates that despite avoiding N dilution, increased damage by herbivores will likely occur in some legume species (Hamilton et al, 2005;Zavala et al, 2008Zavala et al, , 2009). The response of herbivory to rising [CO 2 ] is highly complex and at this time a clear consensus of the response of herbivores to legumes grown at elevated [CO 2 ] is unclear.…”

Evolutionary context for understanding and manipulating plant responses to past, present and future atmospheric [CO 2 ]

“…However, the changes in hormone signalling and secondary metabolism of soybean grown under elevated [CO 2 ] provide an interesting exception to this rule. When grown at elevated [CO 2 ] in the field, the inducible defence response of soybean to damage by Japanese beetle, induction of a protease inhibitor that hinders the beetles' digestive process, is impaired [146]. Changes in sugar-hormone interactions are thought to underpin the response and may provide another target for enhancing crop production in elevated [CO 2 ].…”