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Light and chloroplast signalling

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Published on 30 May 2018

The role of light and chloroplast signalling in the adaptation of plants and algae to environmental stress

Chloroplasts are essential organelles that are the site of photosynthesis in green plants and algae. By capturing sunlight photosynthesis is the primary source of energy for the whole biosphere. Chloroplasts are at the heart of plant energy metabolism and are particularly sensitive to changes in the environment (such as light intensity) and the specific nutrient requirements of the plant. We want to find out how chloroplasts are involved in sensing environmental stress, and how they process and relay this information to the surrounding cytosol and the nucleus to mediate stress adaptationr.

Ancient signalling pathways within the chloroplast

​​Chloroplasts were formed when a eukaryotic cell swallowed a cyanobacterium more than one billion years ago. Today bacteria-like processes including photosynthesis, transcription and translation continue within the chloroplast, with the addition of n​ew eukaryotic processes such as hormone and starch metabolism. Remarkably the chloroplast has also retained ancient stress signalling pathways that were present in its cyanobacterial ancestor. We are currently studying how one of these pathways controls chloroplast function to mediate stress adaptation ​.​

Researchers involved :
Ben Field (PI),
Benoit Menand (PI),
Stefano Caffarri (PI),
Seddik Harchouni (PhD), Rikhia Majumder (PhD)

​Funding : CHLORO_SAP ANR, SIGNAUX_BIONRJ, SIGNAUX_BIONRJ ANR, G4PLAST ANR
ReportMeasurement of photosynthetic activity
  • Chlorophyll fluorescence in wild type and mutant Arabidopsis plants
    Picture copyright: Ben FIELD/ CNRS
    Chlorophyll fluorescence in wild type and mutant Arabidopsis plantsView in full screen
  • A nitrogen starved Arabidopsis seedling
    Picture copyright: Ben FIELD/ CNRS
    A nitrogen starved Arabidopsis seedlingView in full screen
  • Chlorophyll fluorescence imaging of Arabidopsis seedlings
    Picture copyright: Ben FIELD/ CNRS
    Chlorophyll fluorescence imaging of Arabidopsis seedlingsView in full screen
Selected Publications :
  • Field B (2018) Green magic: regulation of the chloroplast stress response by (p)ppGpp in plants and algae. Journal of Experimental Botany. Review. Link
  • Abdelkefi H, Sugliani M, Ke H, Harchouni S, Soubigou-Taconnat L, Citerne S, Mouille G, Fakhfakh H, Robaglia C, Field B. (2017) Guanosine tetraphosphate modulates salicylic acid signaling and the resistance of Arabidopsis thaliana to Turnip Mosaic Virus. Molecular Plant Pathology Link
  • Sugliani M, Abdelkefi H, Ke H, Bouveret E, Robaglia C, Caffarri S, Field B. (2016) An Ancient Bacterial Signaling Pathway Regulates Chloroplast Function to Influence Growth and Development in Arabidopsis. Plant Cell. 28:661-79 Link

Light signalling

Plants perceive light in the chloroplasts and also in the cytosol by photoreceptor proteins such as the phytochromes. We have shown that changes in light intensity leads to a translational response in the cytosol that affects the accumulation of nuclear-encoded chloroplast proteins such as the ELIPs and LHCs. We are currently investigating these and other posttranscriptional responses that follow changes in light intensity and quality ​.

Researchers involved : Christophe Laloi (PI/PL), Laura Dinmet, Louis Valentin Meteignier

Publication
  • Floris M, Bassi R, Robaglia C, Alboresi A, Lanet E (2013) Post-transcriptional control of light-harvesting genes expression under light stress. Plant Mol Biol. 82(1-2):147-54

Chromatin and transcription-based photooxidative stress response

Most environmental constraints lead to a situation where light energy is absorbed in excess, hence resulting in the overproduction of reactive oxygen species (ROS) inside the chloroplast. ROS originating from the chloroplast in response to high light and abiotic stress have been shown to activate specific nuclear genes. A genetic screen aimed at identifying signaling components that regulate ROS-responsive nuclear genes in Arabidopsis thaliana, has revealed the central role of the plant topoisomerase VI (Topo VI) as a key regulator in the plant response to adverse environmental conditions (Baruah et al, 2009; Šimková et al., 2012).  Our current research is aimed at elucidating the molecular mechanisms by which Topo VI and other associated chromatin factors regulate ROS-responsive gene expression changes in response to abiotic stresses of chloroplastic origin. Knowing that the production of ROS is a common feature of most abiotic stresses, results from the study of this model system may disclose widely-spread molecular mechanisms of the plant response and adaptation to adverse environmental conditions.

Researchers involved : Christophe Laloi (PI/PL), Laura Dinmet
     
Projets : CHROS, SLOSAM

Publications :

  • Simkova, K., Moreau, F., Pawlak, P., Vriet, C., Baruah, A., Alexandre, C., Hennig, L., Apel, K. And Laloi, C. (2012) Integration of stress-related and reactive oxygen species-mediated signals by Topoisomerase VI in Arabidopsis thaliana. Proc. Natl. Acad. Sci. USA 109(40), 16360-16365.
  • Baruah, A., Simkova, K., Apel, K. And Laloi, C. (2009) Arabidopsis mutants reveal multiple singlet oxygen signaling pathways involved in stress response and development. Plant Mol. Biol. 70(5),547-563.