Know more

Our use of cookies

Cookies are a set of data stored on a user’s device when the user browses a web site. The data is in a file containing an ID number, the name of the server which deposited it and, in some cases, an expiry date. We use cookies to record information about your visit, language of preference, and other parameters on the site in order to optimise your next visit and make the site even more useful to you.

To improve your experience, we use cookies to store certain browsing information and provide secure navigation, and to collect statistics with a view to improve the site’s features. For a complete list of the cookies we use, download “Ghostery”, a free plug-in for browsers which can detect, and, in some cases, block cookies.

Ghostery is available here for free:

You can also visit the CNIL web site for instructions on how to configure your browser to manage cookie storage on your device.

In the case of third-party advertising cookies, you can also visit the following site:, offered by digital advertising professionals within the European Digital Advertising Alliance (EDAA). From the site, you can deny or accept the cookies used by advertising professionals who are members.

It is also possible to block certain third-party cookies directly via publishers:

Cookie type

Means of blocking

Analytical and performance cookies

Google Analytics

Targeted advertising cookies


The following types of cookies may be used on our websites:

Mandatory cookies

Functional cookies

Social media and advertising cookies

These cookies are needed to ensure the proper functioning of the site and cannot be disabled. They help ensure a secure connection and the basic availability of our website.

These cookies allow us to analyse site use in order to measure and optimise performance. They allow us to store your sign-in information and display the different components of our website in a more coherent way.

These cookies are used by advertising agencies such as Google and by social media sites such as LinkedIn and Facebook. Among other things, they allow pages to be shared on social media, the posting of comments, and the publication (on our site or elsewhere) of ads that reflect your centres of interest.

Our EZPublish content management system (CMS) uses CAS and PHP session cookies and the New Relic cookie for monitoring purposes (IP, response times).

These cookies are deleted at the end of the browsing session (when you log off or close your browser window)

Our EZPublish content management system (CMS) uses the XiTi cookie to measure traffic. Our service provider is AT Internet. This company stores data (IPs, date and time of access, length of the visit and pages viewed) for six months.

Our EZPublish content management system (CMS) does not use this type of cookie.

For more information about the cookies we use, contact INRA’s Data Protection Officer by email at or by post at:

24, chemin de Borde Rouge –Auzeville – CS52627
31326 Castanet Tolosan CEDEX - France

Dernière mise à jour : Mai 2018

Menu Institutions

SPS - Saclay Plant Sciences

The discovery of the chloroplast unfolded protein response - Silvia Ramundo

March 2, 2021 - 4PM - Online

Silvia Ramundo
An ongoing scientific journey to understand how photosynthetic organisms deal with damaged proteins and membranes in their most unique compartment, the chloroplast

Silvia Ramundo
(University of California, San Francisco / Howard Hughes Medical Institute, USA)

Life on Earth crucially depends on photosynthesis –the process by which the energy of sunlight is harnessed, converting atmospheric carbon dioxide and water into sugars and oxygen. In plants and algae, photosynthesis occurs in a specialized cell compartment, the chloroplast, where complex molecular machines absorb light and channel its energy into chemical reactions. These machines are almost entirely composed of proteins that have to be quickly assembled and replaced when damaged.           

We discovered that, when overloaded with misfolded proteins, the chloroplast sends signals to activate an evolutionarily conserved nuclear gene expression program, dubbed the “chloroplast unfolded protein response” (or cpUPR for short), leading to the production of specialized factors that help protect and repair the chloroplast (1).

Through a forward genetic screen in the green alga Chlamydomonas reinhardtii, we identified Mars1, a previously uncharacterized protein kinase, as the first essential signaling component of this novel intracellular communication route (2). Lack of cpUPR induction in MARS1 mutant cells impairs their ability to cope with chloroplast stress, including exposure to excessive light –a condition where the production of unstable oxygen molecules makes chloroplast proteins particularly vulnerable to damage. These findings highlight the physiological importance of the chloroplast unfolded protein response in mitigating chloroplast proteotoxic stress.

We are currently advancing our mechanistic understanding of the cpUPR by focusing on three synergistic aims: the structural and functional dissection of Mars1, the identification of other cpUPR signaling components, and the investigation of the many yet-uncharacterized genes activated during the cpUPR.                        

Our ultimate goal is to unravel how the presence of unfolded proteins inside the chloroplast is sensed, how the signals are transduced across compartmental boundaries, and to what extent the genes activated during this response help plant cells to adapt to stress.


1) Ramundo S, Casero D, Mühlhaus T, Hemme D, Sommer F, Crèvecoeur M, Rahire M, Schroda M, Rusch J, Goodenough U, Pellegrini M, Perez-Perez ME, Crespo JL, Schaad O, Civic N, Rochaix JD. (2014). Conditional Depletion of the Chlamydomonas Chloroplast ClpP Protease Activates Nuclear Genes Involved in Autophagy and Plastid Protein Quality Control. Plant Cell. 26(5):2201-2222. doi: 10.1105/tpc.114.124842. PMID: 24879428

2) Perlaza K, Toutkoushian H, Boone M, Lam M, Iwai M, Jonikas MC, Walter P, Ramundo S. (2019). The Mars1 kinase confers photoprotection through signaling in the chloroplast unfolded protein response. eLife. 2019;8:e49577. doi: 10.7554/eLife.49577. PMID: 31612858