Independent action between DvSnf7 RNA and Cry3Bb1 protein in southern corn rootworm, Diabrotica undecimpunctata howardi and Colorado potato beetle, Leptinotarsa decemlineata

PLoS One. 2015 Mar 3;10(3):e0118622. doi: 10.1371/journal.pone.0118622. eCollection 2015.

Abstract

In recent years, corn rootworm (CRW)-resistant maize events producing two or more CRW-active Bt proteins have been commercialized to enhance efficacy against the target pest(s) by providing multiple modes of action (MoA). The maize hybrid MON 87411 has been developed that produces the CRW-active Cry3Bb1 Bt protein (hereafter Cry3Bb1) and expresses a RNAi-mediated MoA that also targets CRW. As part of an environmental risk assessment for MON 87411, the potential for an interaction between the CRW-active DvSnf7 RNA (hereafter DvSnf7) and Cry3Bb1 was assessed in 12-day diet incorporation bioassays with the southern corn rootworm (SCR, Diabrotica undecimpunctata howardi). The potential for an interaction between DvSnf7 and Cry3Bb1 was evaluated with two established experimental approaches. The first approach evaluated each substance alone and in combination over three different response levels. For all three response levels, observed responses were shown to be additive and not significantly different from predicted responses under the assumption of independent action. The second approach evaluated the potential for a fixed sub-lethal concentration of Cry3Bb1 to decrease the median lethal concentration (LC50) of DvSnf7 and vice-versa. With this approach, the LC50 value of DvSnf7 was not altered by a sub-lethal concentration of Cry3Bb1 and vice-versa. In addition, the potential for an interaction between the Cry3Bb1 and DvSnf7 was tested with Colorado potato beetle (CPB, Leptinotarsa decemlineata), which is sensitive to Cry3Bb1 but not DvSnf7. CPB assays also demonstrated that DvSnf7 does not alter the activity of Cry3Bb1. The results from this study provide multiple lines of evidence that DvSnf7 and Cry3Bb1 produced in MON 87411 have independent action.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Chimera
  • Coleoptera / drug effects*
  • Coleoptera / growth & development
  • Endotoxins / biosynthesis
  • Endotoxins / genetics
  • Endotoxins / isolation & purification
  • Endotoxins / toxicity*
  • Gene Expression
  • Larva / drug effects
  • Larva / growth & development
  • Pest Control, Biological*
  • Plants, Genetically Modified / genetics
  • Plants, Genetically Modified / immunology
  • Plants, Genetically Modified / parasitology
  • RNA, Small Interfering / biosynthesis
  • RNA, Small Interfering / genetics
  • RNA, Small Interfering / isolation & purification
  • RNA, Small Interfering / toxicity*
  • Solanum tuberosum / genetics
  • Solanum tuberosum / immunology
  • Solanum tuberosum / parasitology
  • Transgenes
  • Zea mays / genetics
  • Zea mays / immunology
  • Zea mays / parasitology

Substances

  • Cry3Bbl endotoxin, Bacillus thuringiensis
  • Endotoxins
  • RNA, Small Interfering

Grants and funding

Monsanto Company funded this study. The funder provided support in the form of salaries for all authors, but did not have any additional role in the study design, data collection and analysis, decision to publish, or preparation of the manuscript. The specific roles of these authors are articulated in the ‘author contributions’ section.