Integration of stress-related and reactive oxygen species-mediated signals by Topoisomerase VI in Arabidopsis thaliana
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2012-10
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Journal Article
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Abstract
Environmental stress often leads to an increased production of reactive oxygen species that are involved in plastid-to-nucleus retrograde signaling. Soon after the release of singlet oxygen (¹O₂) in chloroplasts of the flu mutant of Arabidopsis, reprogramming of nuclear gene expression reveals a rapid transfer of signals from the plastid to the nucleus. We have identified extraplastidic signaling constituents involved in ¹O₂-initiated plastid-to-nucleus signaling and nuclear gene activation after mutagenizing a flu line expressing the luciferase reporter gene under the control of the promoter of a ¹O₂-responsive AAA-ATPase gene (At3g28580) and isolating second-site mutations that lead to a constitutive up-regulation of the reporter gene or abrogate its ¹O₂-dependent up-regulation. One of these mutants, caa39, turned out to be a weak mutant allele of the Topoisomerase VI (Topo VI) A-subunit gene with a single amino acid substitution. Transcript profile analysis of flu and flu caa39 mutants revealed that Topo VI is necessary for the full activation of AAA-ATPase and a set of ¹O₂-responsive transcripts in response to ¹O₂. Topo VI binds to the promoter of the AAA-ATPase and other ¹O₂-responsive genes, and hence could directly regulate their expression. Under photoinhibitory stress conditions, which enhance the production of ¹O₂ and H₂O₂, Topo VI regulates ¹O₂-responsive and H₂O₂-responsive genes in a distinct manner. These results suggest that Topo VI acts as an integrator of multiple signals generated by reactive oxygen species formed in plants under adverse environmental conditions.
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published
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109 (40)
Pages / Article No.
16360 - 16365
Publisher
National Academy of Sciences
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Subject
Oxidative stress; Light stress; Cell death