Development of Selectable Marker-Free Transgenic Rice Plants with Enhanced Seed Tocopherol Content through FLP/FRT-Mediated Spontaneous Auto-Excision

PLoS One. 2015 Jul 14;10(7):e0132667. doi: 10.1371/journal.pone.0132667. eCollection 2015.

Abstract

Development of marker-free transgenic plants is a technical alternative for avoiding concerns about the safety of selectable marker genes used in genetically modified (GM) crops. Here, we describe the construction of a spontaneous self-excision binary vector using an oxidative stress-inducible modified FLP/FRT system and its successful application to produce marker-free transgenic rice plants with enhanced seed tocopherol content. To generate selectable marker-free transgenic rice plants, we constructed a binary vector using the hpt selectable marker gene and the rice codon-optimized FLP (mFLP) gene under the control of an oxidative stress-inducible promoter between two FRT sites, along with multiple cloning sites for convenient cloning of genes of interest. Using this pCMF binary vector with the NtTC gene, marker-free T1 transgenic rice plants expressing NtTC were produced by Agrobacterium-mediated stable transformation using hygromycin as a selective agent, followed by segregation of selectable marker genes. Furthermore, α-, γ-, and total tocopherol levels were significantly increased in seeds of the marker-free transgenic TC line compared with those of wild-type plants. Thus, this spontaneous auto-excision system, incorporating an oxidative stress-inducible mFLP/FRT system to eliminate the selectable marker gene, can be easily adopted and used to efficiently generate marker-free transgenic rice plants. Moreover, nutritional enhancement of rice seeds through elevation of tocopherol content coupled with this marker-free strategy may improve human health and public acceptance of GM rice.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Codon / genetics
  • DNA Nucleotidyltransferases / genetics
  • DNA, Bacterial / genetics
  • Genetic Markers
  • Genetic Vectors
  • Humans
  • Oryza / genetics*
  • Oryza / metabolism*
  • Oxidative Stress
  • Plants, Genetically Modified
  • Promoter Regions, Genetic
  • Seeds / metabolism
  • Tocopherols / metabolism*
  • Transformation, Genetic

Substances

  • Codon
  • DNA, Bacterial
  • Genetic Markers
  • T-DNA
  • DNA Nucleotidyltransferases
  • FLP recombinase
  • Tocopherols

Grants and funding

This study was supported by a grant from the Research Program for Agricultural Science & Technology Development (Project No. PJ010902) of the National Academy of Agricultural Science and the Next-Generation BioGreen 21 Program (Plant Molecular Breeding Center No. PJ008021), Rural Development Administration, Republic of Korea. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.