Faites connaître cette offre !
Reference : UMR9198-CECMAR-007
Workplace : SACLAY
Date of publication : Tuesday, June 8, 2021
Scientific Responsible name : Anja KRIEGER-LISZKAY
Type of Contract : PhD Student contract / Thesis offer
Contract Period : 36 months
Start date of the thesis : 1 October 2021
Proportion of work : Full time
Remuneration : 2 135,00 € gross monthly
Description of the thesis topic
In nature, plants are exposed to fluctuations in light intensity. Plants must have enough pigments to grow in dim light, but too much bright light causes damage the photosynthetic machinery and reduces plant growth. The additional production of ATP by alternative electron transport pathways is vital for preventing damage. Cyclic (CET) and pseudocyclic electron transport (PCET) are attractive targets for enhancing stress resistance in crops and improving plant productivity. The overall aims of the project are (1) to biochemically characterize the PGR5 protein and to test the hypothesis that the PGR5 protein plays a direct role in CET in plants and cyanobacteria and (2) perform a systematic analysis of chloroplast redox networks with specific focus on the role of members of the thioredoxin protein family in regulating CET and PCET. We will study the cyanobacterium Synechocystis PCC 6803 as a prokaryotic model that performs oxygenic photosynthesis and the higher model plant Arabidopsis thaliana.
CET has been shown to be crucial under fluctuating light while PCET is stimulated by short photoperiods. Cyanobacterial mutants lacking Pgr5, NDH and the proposed PGRL1 homologue plus equivalent Arabidopsis mutants will be studied. Mutants affected in the thioredoxin system will be subjected to fluctuating light to test the redox regulation of the CET and PCET pathways and to study the importance of CET and PCET for growth. Cyanobacterial mutants lacking homologues of the thioredoxin system will be analyzed. Photosynthetic performance will be monitored by chlorophyll fluorescence. CET will be studied by transient absorption changes (ECS, KLAS-NIR-PAM). The reduction state of the PSI subunits containing a disulphide bridge in Arabidopsis mutants lacking the elements of the thioredoxin system will be detected by standard gel shift assays. PCET will be determined via O2 consumption in the light and by a spin trapping EPR spectroscopy to detect ROS.
The Institute for Integrative Biology of the Cell (I2BC, https://www.i2bc.paris-saclay.fr/) is a joint research unit under the supervision of the CEA, the CNRS and the University of Paris-Saclay. Within the B3S Department (Biochemistry, Biophysics, Structural Biology), the "Photobiology, Photosynthesis, Photocatalysis" group (PPP) is a very international team. It consists of 8 permanent scientists with expertise in biology, chemistry and biophysics.The main topics are natural and artificial photosynthesis. At present 3 PhD students are working in this team.
We talk about it on Twitter!