Physiological ecology - Original Paper

Oecologia

, Volume 161, Issue 1, pp 35-41

First online:

Role of cysteine proteinase inhibitors in preference of Japanese beetles (Popillia japonica) for soybean (Glycine max) leaves of different ages and grown under elevated CO2

  • Jorge A. ZavalaAffiliated withInstitute for Genomic Biology, University of IllinoisFacultad de Agronomia, UBA, CONICET
  • , Clare L. CasteelAffiliated withInstitute for Genomic Biology, University of IllinoisDepartment of Plant Biology, University of Illinois
  • , Paul D. NabityAffiliated withInstitute for Genomic Biology, University of IllinoisDepartment of Plant Biology, University of Illinois
  • , May R. BerenbaumAffiliated withInstitute for Genomic Biology, University of IllinoisDepartment of Entomology, University of Illinois
  • , Evan H. DeLuciaAffiliated withInstitute for Genomic Biology, University of IllinoisDepartment of Plant Biology, University of Illinois Email author 

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Abstract

Elevated levels of CO2, equivalent to those projected to occur under global climate change scenarios, increase the susceptibility of soybean foliage to herbivores by down-regulating the expression of genes related to the defense hormones jasmonic acid and ethylene; these in turn decrease the gene expression and activity of cysteine proteinase inhibitors (CystPIs), the principal antiherbivore defenses in foliage. To examine the effects of elevated CO2 on the preference of Japanese beetle (JB; Popillia japonica) for leaves of different ages within the plant, soybeans were grown at the SoyFACE facility at the University of Illinois at Urbana-Champaign. When given a choice, JB consistently inflicted greater levels of damage on older leaves than on younger leaves, and there was a trend for a greater preference for young leaves grown under elevated CO2 compared to those grown under ambient CO2. More heavily damaged older leaves and those grown under elevated CO2 had reduced CystPI activity, and JB that consumed leaves with lower CystPI activity had correspondingly greater gut proteinase activity. Younger leaves with higher CystPI activity and photosynthetic rates may contribute disproportionately to plant fitness and are more protected against herbivore attack than older foliage. Cysteine proteinase inhibitors are potent defenses against JB, and the effectiveness of this defense is modulated by growth under elevated CO2 as well as leaf position.

Keywords

Within-plant movement Plant–insect interactions Global change Plant defenses Optimal defense theory Free-air CO2 enrichment