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The Fed-1 (CAUU)4 element is a 5' UTR dark-responsive mRNA instability element that functions independently of

Sumana Bhat1, Li Tang, Angela D Krueger

  • 1Department of Biochemistry and Molecular Biology, Oklahoma State University, 246 Noble Research Center, Stillwater, OK 74078, USA.

Plant Molecular Biology
|April 2, 2005
PubMed

Insights

Darkness destabilizes pea Ferredoxin-1 (Fed-1) mRNA in tobacco, but specific (CAUU) repeats in the 5' UTR enhance light-responsive accumulation and stability. This light regulation is independent of translation.

Area of Science:

  • Plant molecular biology
  • Gene expression regulation
  • mRNA stability

Background:

  • Pea Ferredoxin-1 (Fed-1) mRNA stability and translation are rapidly affected by darkness in transgenic tobacco.
  • The 5' untranslated region (5' UTR) of mRNAs plays a crucial role in post-transcriptional regulation.

Purpose of the Study:

  • To investigate the role of (CAUU) repeats in the 5' UTR of Fed-1 mRNA in light-responsive regulation.
  • To determine the minimal sequence and repeat number required for light-regulated mRNA accumulation.

Main Methods:

  • Direct mRNA half-life measurements in transgenic tobacco.
  • Site-directed mutagenesis of (CAUU) repeats in the Fed-1 5' UTR.
  • Fusion of Fed-1 5' UTR sequences to a heterologous plant mRNA.
  • In vitro ribonuclease accessibility assays.

Main Results:

  • Mutation of the (CAUU)4 repeat stabilizes Fed-1 mRNA in darkness.
  • At least three but fewer than 11 (CAUU) repeats are necessary for full light-responsive accumulation.
  • A 26-nucleotide sequence containing (CAUU)4 is sufficient to confer light regulation to a heterologous mRNA.
  • Mutating the (CAUU)4 repeat alters its accessibility to RNases, suggesting a role for its structure in regulating instability.

Conclusions:

  • The (CAUU)n repeats in the pea Fed-1 mRNA 5' UTR are critical for light-regulated mRNA accumulation and stability in transgenic tobacco.
  • The specific number and arrangement of these repeats influence the degree of light responsiveness.
  • Dark-induced mRNA instability is likely an independent event regulated by darkness, not directly linked to translation status.

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