Kempema, Louisa , Zarate, Sonia , Walling, Linda .
Silverleaf whiteflies induce salicylic acid defenses and suppress effectual jasmonic acid defenses.
Using Affymetrix ATH-1 arrays the changes in the Arabidopsis transcriptome to silverleaf whitefly (Bemisia tabaci type B, SLWF) nymph feeding was assessed. Distinctions from aphid and larval feeding were noted. While aphids suppressed and Tricoplusia ni activated sulfur and glucosinolate metabolism genes, SLWFs evaded activation of these defenses. In addition to the RNA profile distinctions, analysis of SLWF performance on wild-type and pad4 mutants suggest aphid and SLWF interactions with Arabidopisis were distinct. While pad4-1 mutants were more susceptible to aphids, silverleaf whitefly development on pad4-1 and wild type plants was similar. The basal defenses important in curtailing the development of the phloem-feeding silverleaf whitefly on Arabidopsis thaliana were investigated. Sentinel defense gene RNAs were monitored in SLWF-infested and control plants. SA-responsive gene transcripts accumulated locally (PR1, BGL2, PR5, SID2, EDS5, PAD4) and systemically (PR1, BGL2, PR5) during SLWF nymph feeding. In contrast, JA- and ET-dependent RNAs (PDF1.2, VSP, HEL, THI2.1, FAD3, ERS1, ERF1) were repressed or not modulated in SLWF-infested leaves. To test for a role of SA and JA pathways in basal defense, SLWF development on mutant and transgenic lines that constitutively activate or impair defense pathways was determined. By monitoring the percentage of SLWF nymphs in each instar, we show that mutants, which activate SA defenses (cim10) or impair JA-defenses (coi1), accelerated SLWF nymphal development. Reciprocally, mutants that activate JA defenses (cev1) or impair SA defenses (npr1, NahG) slowed SLWF nymphal development. Furthermore, when npr1 plants, which do not activate downstream SA defenses, were treated with MeJA, a dramatic delay in nymph development was observed. Collectively these results showed that SLWF-repressed, JA-regulated defenses were associated with basal defense to the SLWF.
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1 - University of California at Riverside, Botany and Plant Sciences
2 - University of California at Riverside, Botany and Plant Sciences, Riverside, CA, 92506, USA
Presentation Type: Plant Biology Abstract
Location: Exhibit Hall (Northeast, Southwest & Southeast)/Hilton
Date: Sunday, July 8th, 2007
Time: 8:00 AM