Casteel, Clare , Zavala, Jorge , Berenbaum, May , De Lucia, Evan .
Modulation of soybean, Glycine max defenses to herbivory by Japanese beetles (Popillia japonica) under ambient and elevated atmospheric CO2.
Anthropogenic greenhouse gases are increasing in the troposphere and may alter plant-insect interactions in agro-ecosystems. Elevated CO2 increased Japanese beetle (Popillia japonica Newman) colonization and herbivory in soybean (Glycine max) agro-ecosystem, suggesting that elevated CO2 decreased plant defenses. To test this hypothesis and explain the mechanism behind it, we examined Japanese beetle herbivory at the soybean free-air concentration site (soyFACE), under conditions of either ambient or elevated CO2. The expression of over 37,000 transcripts after beetle attack was quantified in soybean leaves with Affymetrix microarrays and the accumulation of the hormone jasmonic acid (JA) and the defense compounds cysteine proteinase inhibitors (CystPI) determined. Interestingly, elevated CO2 down regulated the expression of genes related to JA and CystPI and decreased the accumulation of these products in the leaves. Elicitation of leaves by either beetle attack or methyl jasmonate application increased both transcripts and metabolites (JA and CystPI) accumulation, but with lower levels in plants grown in elevated than in ambient CO2. Furthermore, the activity of the digestive enzyme cysteine was lower in the guts of beetles that fed on plants grown under elevated than ambient CO2. Changes in tropospheric chemistry associated with global change thus modulates well-established transcriptional responses and allelochemicals that are important to plant defense, and may increase the susceptibility of soybean crops to insect herbivores in the future.
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1 - University of Illinois - Urbana Champaign, Institute for Genomic Biology, 1500 Igb, 1207 W. Gregory Ave., Urbana, Il, 61801, Usa
2 - University of Illinois - Urbana Champaign, Institute for Genomic Biology
3 - University of Illinois - Urbana Champaign, Entomology
Presentation Type: Plant Biology Abstract
Location: Exhibit Hall (Northeast, Southwest & Southeast)/Hilton
Date: Sunday, July 8th, 2007
Time: 8:00 AM