Molecular and General Genetics MGG

, Volume 248, Issue 6, pp 649–656 | Cite as

Transgene inactivation inPetunia hybrida is influenced by the properties of the foreign gene

  • Paula Elomaa
  • Yrjö Helariutta
  • Mika Kotilainen
  • Teemu H. Teeri
  • Robert J. Griesbach
  • Pauli Seppänen
Original Paper

Abstract

Petunia mutant RL01 was transformed with maizeA1 and gerberagdfr cDNAs, which both encode dihydroflavonol-4-reductase (DFR) activity. The sameAgrobacterium vector and the same version of the CaMV 35S promoter were used in both experiments. Transformation with the cDNAs resulted in production of pelargonidin pigments in the transformants. However, theA1 andgdfr transformants showed clearly different phenotypes. The flowers of the primaryA1 transformants were pale and showed variability in pigmentation during their growth, while the flowers of thegdfr transformants showed intense and highly stable coloration. The color difference in the primary transformants was reflected in the expression levels of the transgenes as well as in the levels of anthocyanin pigment. As previously reported by others, the instability in pigmentation in theA1 transformants was more often detected in clones with multiple copies of the transgene and was associated with methylation of the 35S promoter and of the transgene cDNA itself. In thegdfr transformants, the most intense pigmentation was observed in plants with multiple transgenes in their genome. Only rarely was partial methylation of the 35S promoter detected, while thegdfr cDNA always remained in an unmethylated state. We conclude that the properties of the transgene itself strongly influence the inactivation process. The dicotyledonousgdfr cDNA with a lower GC content and fewer possible methylation sites is more ‘compatible’ the genomic organization of petunia and this prevents it being recognized as a foreign gene and hence silenced by methylation.

Key words

Transgenic plants Gene silencing Methylation GC content 

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Copyright information

© Springer-Verlag 1995

Authors and Affiliations

  • Paula Elomaa
    • 1
  • Yrjö Helariutta
    • 1
  • Mika Kotilainen
    • 1
  • Teemu H. Teeri
    • 1
  • Robert J. Griesbach
    • 2
  • Pauli Seppänen
    • 3
  1. 1.Institute of BiotechnologyUniversity of HelsinkiFinland
  2. 2.U.S. Department of AgricultureFloral/Nursery Plants Research, U.S. National ArboretumBeltsvilleUSA
  3. 3.Kemira Agro Oy, Espoo Research CentreEspooFinland

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