Zavala, Jorge , Casteel, Clare , Berenbaum, May , De Lucia, Evan .
Elevated CO2 increases susceptibility of soybean to natural herbivores by defeating induction of cysteine proteinase inhibitors.
By changing leaf chemistry exposure to elevated CO2, an important element of global change, may fundamentally alter the relationship between plants and herbivorous insects. Under natural field conditions, elevated CO2 not only increased susceptibility of soybean (Glycine max) to herbivory by the invasive species Japanese beetle (Popillia japonica), but also enhanced the performance of these beetles. To understand the mechanisms governing increased susceptibility to herbivores, we determined gene expression and activity of cysteine proteinase inhibitors (CystPIs) of soybeans grown in under otherwise typical field conditions but with free-air CO2 enrichment. In addition, we determined the expression of genes that regulate the accumulation of the defense hormones jasmonic acid and ethylene. Elevated CO2 not only down-regulated cystpi, lox and acc transcripts, but also decreased the activity of CystPIs. Moreover, beetle attack increased CystPIs activity and transcripts on plants grown either on elevated or ambient CO2, but with lower levels of induction in plants grown under elevated CO2. Although the activity was higher in younger than older leaves, elevated CO2 decreased constitutive levels of CystPIs and reduced beetle-elicited CystPIs activity of both young and fully expanded leaves. Interestingly, the cysteine activity in the gut of Japanese beetles that fed on soybean crop grown under elevated CO2 was higher than those that fed on plants grown on ambient CO2. Our results suggest that elevated CO2 increased the susceptibility of soybean to invasive insects by down-regulating the expression of hormones related with defense, which down-regulate the important defense CystPIs against beetles.
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1 - University of Illinois, Institute for Genomic Biology, 1206 W Gregory Dr, Urbana, Illinois, 61801, USA
2 - University of Illinois, Institute for Genomic Biology
3 - University of Illinois, Entomology and Institute for Genomic Biology
4 - University of Illinois, Plant Biology and Institute fro Genomic Biology
cysteine proteinase inhibitors
Presentation Type: ASPB Minisymposium
Location: Continental A/Hilton
Date: Monday, July 9th, 2007
Time: 10:40 AM