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Circadian and Plastid Signaling Pathways Are Integrated to Ensure Correct Expression of the CBF and COR Genes during Photoperiodic Growth
Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC). Copenhagen Plant Science Centre, University of Copenhagen.ORCID iD: 0000-0003-0947-2648
Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).ORCID iD: 0000-0002-7476-1043
Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).ORCID iD: 0000-0002-2661-5535
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2016 (English)In: Plant Physiology, ISSN 0032-0889, E-ISSN 1532-2548, Vol. 171, no 2, 1392-1406 p.Article in journal (Refereed) Published
Abstract [en]

The circadian clock synchronizes a wide range of biological processes with the day/night cycle, and correct circadian regulation is essential for photosynthetic activity and plant growth. We describe here a mechanism where a plastid signal converges with the circadian clock to fine-tune the regulation of nuclear gene expression in Arabidopsis (Arabidopsis thaliana). Diurnal oscillations of tetrapyrrole levels in the chloroplasts contribute to the regulation of the nucleus-encoded transcription factors C-REPEAT BINDING FACTORS (CBFs). The plastid signal triggered by tetrapyrrole accumulation inhibits the activity of cytosolic HEAT SHOCK PROTEIN90 and, as a consequence, the maturation and stability of the clock component ZEITLUPE (ZTL). ZTL negatively regulates the transcription factor LONG HYPOCOTYL5 (HY5) and PSEUDO-RESPONSE REGULATOR5 (PRR5). Thus, low levels of ZTL result in a HY5- and PRR5-mediated repression of CBF3 and PRR5-mediated repression of CBF1 and CBF2 expression. The plastid signal thereby contributes to the rhythm of CBF expression and the downstream COLD RESPONSIVE expression during day/night cycles. These findings provide insight into how plastid signals converge with, and impact upon, the activity of well-defined clock components involved in circadian regulation.

Place, publisher, year, edition, pages
2016. Vol. 171, no 2, 1392-1406 p.
National Category
Botany
Identifiers
URN: urn:nbn:se:umu:diva-125464DOI: 10.1104/pp.16.00374ISI: 000380699200048PubMedID: 27208227OAI: oai:DiVA.org:umu-125464DiVA: diva2:968725
Available from: 2016-09-12 Created: 2016-09-12 Last updated: 2016-09-13Bibliographically approved
In thesis
1. Coordination of two different genomes in response to light and stress
Open this publication in new window or tab >>Coordination of two different genomes in response to light and stress
2016 (English)Doctoral thesis, comprehensive summary (Other academic)
Alternative title[sv]
Hur två olika genom samarbetar under ljus och stress respons
Abstract [en]

About 1.5 billion years ago, a photosynthetic bacteria was engulfed by a eukaryotic cell which initiated a symbiotic relationship and the evolution of the chloroplast as we know it today. The chloroplast has retained its own genome encoding for a number of proteins required for the function of the chloroplast. However, during the evolution most genes were transferred to the nucleus and the chloroplast is thus dependent on the nucleus to provide the majority of proteins necessary for its function. The distribution of genes encoding plastid proteins between two different cellular compartments requires a tight communication in order to coordinate gene expression during different growth conditions. The focus of my PhD studies has been to elucidate signalling pathways between the chloroplast and nucleus that enables the coordination of these two genomes in response to light and stress. The results in this thesis demonstrate that chloroplast retrograde signals triggered by changes in tetrapyrrole levels are important both in response to day-night cycles and during the response to stress. We identified a cytosolic regulatory complex and a novel mechanism that could explain how the tetrapyrrole-mediated signal can be transduced from the plastid to the nucleus and regulate nuclear gene expression in response to changes in the environment. My work further demonstrates that the tetrapyrrole-triggered plastid signalling pathway integrates with the circadian clock in order to fine-tune nuclear gene expression during photoperiodic conditions. These findings provide novel insight into how clock components and plastid signals converge in order to obtain the proper output. I have also examined the regulation of nuclear gene expression in response to redox and early-light signals by identifying transcription factors responding to these signals. My work demonstrates a novel mechanism by which redox-regulation of specific transcription factors directly links cellular redox status to gene regulation. The identified transcription factors were further shown to regulate nuclear genes encoding plastid proteins and they are of particular importance for anterograde control during the early light response and establishment of photomorphogenic growth.

Place, publisher, year, edition, pages
Umeå: Umeå University, 2016. 100 p.
Keyword
Arabidopsis thaliana, chloroplast, cellular communication, tetrapyrrole, circadian clock, oxidative stress, light signalling, gene regulation
National Category
Biochemistry and Molecular Biology
Research subject
Molecular Biology
Identifiers
urn:nbn:se:umu:diva-125373 (URN)978-91-7601-550-6 (ISBN)
External cooperation:
Public defence
2016-10-06, KB3A9, KBC-huset, Umeå, 10:00 (English)
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Available from: 2016-09-15 Created: 2016-09-09 Last updated: 2016-09-15Bibliographically approved

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Norén, LouiseKindgren, PeterStachula, PaulinaRühl, MarkEriksson, Maria E.Hurry, VaughanStrand, Åsa
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