Evolutionary conservation of circadian signalling to chloroplasts by sigma factors

  • David Cuitun Coronado

Student thesis: Doctoral ThesisDoctor of Philosophy (PhD)


Circadian regulation is conserved across the green lineage. Circadian regulation in plants involves a series of signalling pathways that have considerable evolutionarily conservation. There are circadian rhythms of photosynthesis, but the evolution of signalling pathways associated with this process remain poorly understood. I used the basal plant Marchantia polymorpha in combination with phylogenetic analysis to study the nature of signalling pathways that participate in the circadian regulation of photosynthesis. I have developed methods to investigate this process in Marchantia (PAM Fluorescence and Delayed Fluorescence), and identified regulatory features that are conserved with higher plants. Using this, I am identifying aspects of chloroplast function that are required for circadian regulation of photosynthesis.

I also investigated the involvement of nuclear-encoded regulators of chloroplast transcription (sigma factors) in the circadian regulation and some clock genes plus psbD. It remains unknown whether sigma factors in Marchantia are circadian-regulated, whilst others (clock genes and psbD) have been studied previously under different conditions. During those experiments, one question took our attention and we focused to respond it. The question was: How is darkness affecting Marchantia polymorpha? A step to understand the physiology of basal plants. Finally, I prepared the material (plasmids) to obtain mutants of sig5 and sigX.

This work provides insights into conserved mechanisms that couple the circadian clock and photosynthesis, and identifies new mechanisms that are required for this adaptation of plants to the day-night cycle like Marchantia had a circadian rhythm in darkness (delayed fluorescence) or some inhibitors did not have efect in Marchantia (DBMIB) or only in circadian rhythm (lincomycin).
Date of Award2 Dec 2021
Original languageEnglish
Awarding Institution
  • University of Bristol
SupervisorAntony Dodd (Supervisor) & Jill Harrison (Supervisor)

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