Aphids alter host-plant nitrogen isotope fractionation

Alex C.C. Wilson, Leonel Da S.L. Sternberg, Katherine B. Hurley

Research output: Contribution to journalArticle

28 Scopus citations

Abstract

Plant sap-feeding insects and blood-feeding parasites are frequently depleted in 15N relative to their diet. Unfortunately, most fluid-feeder/host nitrogen stable-isotope studies simply report stable-isotope signatures, but few attempt to elucidate the mechanism of isotopic trophic depletion. Here we address this deficit by investigating the nitrogen stable-isotope dynamics of a fluid-feeding herbivore-host plant system: the green peach aphid, Myzus persicae, feeding on multiple brassicaceous host plants. M. persicae was consistently more than 6‰ depleted in 15N relative to their hosts, although aphid colonized plants were 1.5‰ to 2.0‰ enriched in 15N relative to uncolonized control plants. Isotopic depletion of aphids relative to hosts was strongly related to host nitrogen content. We tested whether the concomitant aphid 15N depletion and host 15N enrichment was coupled by isotopic mass balance and determined that aphid 15N depletion and host 15N enrichment are uncoupled processes. We hypothesized that colonized plants would have higher nitrate reductase activity than uncolonized plants because previous studies had demonstrated that high nitrate reductase activity under substrate-limiting conditions can result in increased plant δ 15N values. Consistent with our hypothesis, nitrate reductase activity in colonized plants was twice that of uncolonized plants. This study offers two important insights that are likely applicable to understanding nitrogen dynamics in fluid-feeder/host systems. First, isotopic separation of aphid and host depends on nitrogen availability. Second, aphid colonization alters host nitrogen metabolism and subsequently host nitrogen stable-isotope signature. Notably, this work establishes a metabolic framework for future hypothesis-driven studies focused on aphid manipulation of host nitrogen metabolism.

Original languageEnglish (US)
Pages (from-to)10220-10224
Number of pages5
JournalProceedings of the National Academy of Sciences of the United States of America
Volume108
Issue number25
DOIs
StatePublished - Jun 21 2011

Keywords

  • Host-parasite interaction
  • Nitrogen budget
  • Plant-herbivore interaction
  • Trophic enrichment

ASJC Scopus subject areas

  • General

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