Understanding how plants resist heat stress

PhD co-supervisors:

Ben Field, research director CNRS, HDR.

Helene Javot, research director CEA, HDR.

A chloroplastic signalling pathway mediated by the nucleotide guanosine tetraphosphate (ppGpp), has recently emerged as a major regulator of plastid function and photosynthesis (1). ppGpp signalling is best known in bacteria where ppGpp functions as an allosteric and GTP-competitive regulator of many enzymes including RNA polymerase to promote energy economy and stress acclimation. Over recent years we have pioneered the study of ppGpp signalling in plants, showing that ppGpp accumulation downregulates plastid gene expression, nucleotide metabolism, and photosynthesis (2, 3).

The photosynthetic machinery is well known to be sensitive to high temperatures. Growth at high temperatures reduces photosynthetic activity, although the diversity of plant responses suggests that there is a margin for increasing the performance of plants at higher temperatures. Heat shock can rapidly damage the photosynthetic machinery, causing energy overflow, ROS production, cellular damage and tissue death. We hypothesize that ppGpp signalling plays an important role in regulating chloroplast function and photosynthesis for growth at high temperatures, and during acclimation to episodes of heat shock.

To address this question, we offer a CEA-funded PhD position starting 01/10/2024. The successful candidate will use physiological approaches to understand the role of ppGpp signalling during episodes of heat stress, and study the regulation of the RSH enzymes responsible for ppGpp metabolism using biochemical approaches (4). Notably, we anticipate that the student will also develop new tools using state-of-the-art cloning approaches to follow the regulation of RSH enzymes using microscopy and biochemistry. This project will provide the opportunity to the PhD student to learn advanced analytical techniques, develop expertise quantifying key physiological parameters (photosynthesis), and become familiar with biochemical and imaging techniques for the study of RSH protein regulation.

1.     M. Mehrez, S. Romand, B. Field, New perspectives on the molecular mechanisms of stress signalling by the nucleotide guanosine tetraphosphate (ppGpp), an emerging regulator of photosynthesis in plants and algae. New Phytologist 237, 1086–1099 (2023).

2.     S. Romand, H. Abdelkefi, C. Lecampion, M. Belaroussi, M. Dussenne, B. Ksas, S. Citerne, J. Caius, S. D’Alessandro, H. Fakhfakh, S. Caffarri, M. Havaux, B. Field, A guanosine tetraphosphate (ppGpp) mediated brake on photosynthesis is required for acclimation to nitrogen limitation in Arabidopsis. eLife 11, e75041 (2022).

3.     M. Sugliani, H. Abdelkefi, H. Ke, E. Bouveret, C. Robaglia, S. Caffarri, B. Field, An Ancient Bacterial Signaling Pathway Regulates Chloroplast Function to Influence Growth and Development in Arabidopsis. The Plant cell 28, 661–679 (2016).

4.     S. D’Alessandro, F. Velay, R. Lebrun, M. Mehrez, S. Romand, R. Saadouni, C. Forzani, S. Citerne, M.-H. Montané, C. Robaglia, B. Menand, C. Meyer, B. Field, Post-translational regulation of photosynthetic activity via the TOR kinase in plants. bioRxiv [Preprint] (2023). https://doi.org/10.1101/2023.05.05.539554.

 

Funding category: Contrat doctoral

Contrat Formation par la Recherche CEA (CFR)

PHD title: Doctorat de Biologie

PHD Country: France