Document: PAT-3-42-18

Effects of aphid feeding on expression of multiple defense response pathways in A. thaliana, and the role of mutants in resistance.

MORAN, P.J.* and G.A.THOMPSON

University of Arizona, Tucson, AZ 85721 USA ¹

Abstract:
Plant defensive responses to pathogen infection and herbivory involve at least four signaling pathways. Little is known about the effects of phloem feeding by aphids on resistance responses. RNA blotting and population development bioassays were used to investigate green peach aphid (Myzus persicae) and cabbage aphid (Brevicoryne brassicae) herbivory on leaves of mouse-ear cress (Arabidopsis thaliana). Feeding by green peach aphids increased mRNA levels of the systemic acquired resistance (SAR)-related proteins PR1 and -1,3-glucanase (12- and 22-fold increases, respectively). Two transcripts representing the jasmonic acid (JA)-related responses defensin (an antipathogenic protein) and lipoxygenase showed 2-fold increases, as did phenylalanine ammonia lyase. Transcripts for STP4, a wound- and pathogen-inducible protein involved in sugar turnover, increased 10-fold. B. brevicoryne aphid feeding induced similar patterns of gene induction. Reproduction by M. persicae aphids was not altered on the npr1, eds5, and eds9 (deficient in SAR) or jar1 (deficient in JA perception) mutant lines of A. thaliana relative to wild-type plants. Chemical induction of SAR reduced green peach aphid reproduction by approximately 40% in wild-type but not SAR mutant plants. Treatment with methyl JA had no effect in either wild-type or jar1 plants. Cabbage aphid reproduction was elevated on untreated SAR and JA mutant plants. Phloem feeding by aphids induced at least two plant defense pathways in A. thaliana, and lesions in these pathways influenced herbivore fitness in species-specific ways.

Keywords: aphid, induction, SAR, JA, mutant

This abstract is being presented at: 3:30 PM in session:
HERBIVORE EFFECTS ON PLANTS