The ANR MEDSALT project aims to consolidate and expand a scientific network recently formed with the purpose to use scientific drilling to address the causes, timing, emplacement mechanisms and consequences of the largest and most recent 'salt giant' on Earth: the late Miocene (Messinian) salt deposit in the Mediterranean basin. After obtaining the endorsement of the International Ocean Discovery Program (IODP) on a Multiplatform Drilling Proposal (umbrella proposal) in early 2015, the network is planning to submit a site-specific drilling proposal to drill a transect of holes with the R/V Joides Resolution in the evaporite-bearing southern margin of the Balearic promontory in the Western Mediterranean - the aim is to submit the full proposal before the IODP dealine of April 1st 2017, following the submission of a pre-proposal on October 1st 2015. Four key issues will be addressed: 1) What are the causes, timing and emplacement mechanisms of the Mediterranean salt giant ? 2) What are the factors responsible for early salt deformation and fluid flow across and out of the halite layer ? 3) Do salt giants promote the development of a phylogenetically diverse and exceptionally active deep biosphere ? 4) What are the mechanisms underlying the spectacular vertical motions inside basins and their margins ? Our nascent scientific network will consit of a core group of 22 scientists from 10 countries (7 European + USA + Japan + Israel) of which three french scientists (G. Aloisi, J. Lofi and M. Rabineau) play a leading role as PIs of Mediterranean drilling proposals developed within our initiative. Support to this core group will be provided by a supplementary group of 21 scientists that will provide critical knowledge in key areas of our project. The ANR MEDSALT network will finance key actions that include: organising a 43 participants workshops to strengthen and consolidate the Mediterranean drilling community, supporting the participation of network scientists to seismic well site-survey cruises, organising meetings in smaller groups to work on site survey data and finance trips to the US to defend our drilling proposal in front of the IODP Environmental Protection and Safety Panel (EPSP). The MEDSALT drilling initiative will impact the understanding of issues as diverse as submarine geohazards, sub-salt hydrocarbon reservoirs and life in the deep subsurface. This is a unique opportunity for the French scientific community to play a leading role, next to our international partners, in tackling one of the most intellectually challenging open problems in the history of our planet.

Oxidative stress signalling is an important part of plant responses to numerous environmental conditions that affect plant performance, vigour, and/or yield. Despite intense interest, it remains poorly understood how the effects of increased cellular oxidation caused by compounds such as H2O2 are mediated. A key candidate in transmitting oxidative signals is modified protein thiol/disulfide status, which is regulated by the NADPH-dependent glutathione and thioredoxin (TRX) systems. Recent data obtained by partners involved in this proposal have highlighted functions of the two systems, and interactions between them in stress response and plant development pathways. They also provided a first indication that perturbations in thiol-disulfide systems are important in transmitting H2O2 signals. However, little is known about the functional interplay between the two key thiol systems during oxidative stress. Although recent years have seen the identification of a growing number of target proteins whose thiol status is potentially affected by H2O2, glutathione and TRX, little or nothing is known about oxidative signalling through these pathways in vivo. The principal aims of the present project are to (1) establish the importance of the two thiol systems in oxidative stress signalling, and the interplay between them; (2) analyse the contribution of the enzymes that provide NADPH for the two systems during oxidative stress; and (3) identify candidate proteins that are involved in oxidative signalling though post-translational redox modifications. To achieve these objectives, we will use a combined genetic, transcriptomic, proteomic and biochemical approach. The genetic analysis will be based on the conditional catalase-deficient Arabidopsis mutant, cat2, in which controllable oxidation of NADPH-thiol systems can be triggered by easy modification of external conditions that affect the rate of intracellular H2O2 production. Using mutant lines available in the partner laboratories for glutathione reduction, glutathione synthesis, TRX reduction, and NADPH generation, secondary mutations will be introduced into the cat2 background. By comparison of double mutants with cat2 at the phenotypic, metabolomic, proteomic and transcriptomic levels, we will identify how modified status of specific thiol or NADPH-producing systems regulates the impact of oxidative stress on metabolic and signalling pathways. Quantitative redox proteomic analysis of proteins that are post-translationally modified in the different lines will allow us to identify novel candidates for transmitting oxidative stress signals. The interaction of candidate proteins with TRX or glutathione-dependent glutaredoxins will be analysed using redox-specific yeast-2-hybrid in vivo interaction assays, biochemical test and further genetic approaches. Together, the data will dissect the relative importance of different components of NADPH-thiol systems in oxidative stress and identify proteins with which the systems interact, thus providing incisive new insight into the redox signalling pathways through which stress conditions are perceived by plants.