Plant Molecular Biology

, Volume 62, Issue 1, pp 15–28

Nature of stress and transgene locus influences transgene expression stability in barley

Authors

  • Ling Meng
    • Department of Plant and Microbial BiologyUniversity of California
  • Meira Ziv
    • Department of Plant and Microbial BiologyUniversity of California
    • Department of Plant and Microbial BiologyUniversity of California
Orignal paper

DOI: 10.1007/s11103-006-9000-7

Cite this article as:
Meng, L., Ziv, M. & Lemaux, P.G. Plant Mol Biol (2006) 62: 15. doi:10.1007/s11103-006-9000-7

Abstract

Stress and the nature of the transgene locus can affect transgene expression stability. These effects were studied in two, stably expressing, T6 populations of barley (Hordeum vulgare): bombardment-mediated, multi-copy lines with ubiquitin-driven bar and uidA or single-copy lines from Ds-mediated gene delivery with ubiquitin-driven bar alone. Imposing the environmental stresses, water and nutrient deprivation and heat shock, did not reproducibly affect transgene expression stability; however, high frequencies of heritable transcriptional gene silencing (TGS) occurred following in vitro culture after six generations of stable expression in the multi-copy subline, T3#30, but not in the other lines studied. T3#30 plants with complete TGS had epigenetic modification patterns exactly like those in an identical sibling subline, T3#31, which had significant reduction in transgene expression in the T3 generation and was completely transcriptionally silenced in the absence of imposed stresses in the T6 generation. Complete TGS in T3#30 plants correlated with methylation in the 5′UTR and intron of the ubi1 promoter complex and condensation of chromatin around the transgenes; DNA methylation likely occurred prior to chromatin condensation. Partial TGS in T3#30 also correlated with methylation of the ubi1 promoter complex, as occurred with complete TGS. T3#30 has a complex transgene structure with inverted repeat transgene fragments and a 3′-LTR from a barley retrotransposon, and therefore the transgene locus itself may affect its tendency to silence after in vitro culture and transgene silencing might result from host defense mechanisms activated by changes in plant developmental programming and/or stresses imposed during in vitro growth.

Keywords

BarleyChromatin condensationEnvironmental stressIn vitro cultureDNA methylationTransgene silencing

Abbreviations

2,4-D

2,4-dichlorophenoxyacetic acid

BAP

6-benzylaminopurine

IBA

indole butyric acid

MS

Murishige and Skoog

RWC

relative water content

Copyright information

© Springer Science+Business Media B.V. 2006