The Petrochemistry of Jake_M: A Martian Mugearite

“Jake_M,” the first rock analyzed by the Alpha Particle X-ray Spectrometer instrument on the Curiosity rover, differs substantially in chemical composition from other known martian igneous rocks: It is alkaline (&gt;15% normative nepheline) and relatively fractionated. Jake_M is compositionally similar to terrestrial mugearites, a rock type typically found at ocean islands and continental rifts. By analogy with these comparable terrestrial rocks, Jake_M could have been produced by extensive fractional crystallization of a primary alkaline or transitional magma at elevated pressure, with or without elevated water contents. The discovery of Jake_M suggests that alkaline magmas may be more abundant on Mars than on Earth and that Curiosity could encounter even more fractionated alkaline rocks (for example, phonolites and trachytes).</jats:p

Mars’ Surface Radiation Environment Measured with the Mars Science Laboratory’s Curiosity Rover

The Radiation Assessment Detector (RAD) on the Mars Science Laboratory’s Curiosity rover began making detailed measurements of the cosmic ray and energetic particle radiation environment on the surface of Mars on 7 August 2012. We report and discuss measurements of the absorbed dose and dose equivalent from galactic cosmic rays and solar energetic particles on the martian surface for ~300 days of observations during the current solar maximum. These measurements provide insight into the radiation hazards associated with a human mission to the surface of Mars and provide an anchor point with which to model the subsurface radiation environment, with implications for microbial survival times of any possible extant or past life, as well as for the preservation of potential organic biosignatures of the ancient martian environment.</jats:p

Transport de l'auxine et développement du nodule actinorhizien chez l'arbre tropical Casuarina glauca

Les plantes actinorhiziennes appartiennent à 8 familles d angiosperme et forment une symbiose fixatrice d azote avec l actinomycète du sol Frankia qui aboutit à la formation de nodules au niveau du système racinaire de la plante. Le nodule actinorhizien est considéré comme une racine latérale modifiée car i) il provient de divisions des cellules du péricycle situées en face du pôle de xylème, ii) il possède un méristème apical et un système vasculaire central et iii) chez certaines espèces comme Casuarina glauca une racine nodulaire est produite à l apex de chaque lobe nodulaire. L auxine, et notamment le transport d influx, est impliquée dans la mise en place de la racine latérale. Nous avons donc identifié des gènes de transporteurs d influx d auxine chez la plante actinorhizienne C. glauca et étudié le rôle du transport d influx au cours de la mise en place du nodule actinorhizien. Deux gènes de la famille AUX-LAX codant des transporteurs d influx d auxine ont été identifiés C. glauca. Les profils d expression des gènes CgAUX1 et CgLAX3 sont très conservés entre C. glauca et Arabidopsis thaliana. De plus, des analyses fonctionnelles par complémentation de mutants d A. thaliana ont mis en évidence une équivalence entre CgAUX1 et AtAUX1. Nos études suggèrent également qu il existe une divergence fonctionnelle au sein de la famille AUX-LAX. Nous avons analysé le rôle de ces gènes au cours de la mise en place de la symbiose. Notre étude montre que le gène CgAUX1 est exprimé dans les cellules infectées tout au long de l infection. De plus, le rôle du transport d influx d auxine dans le mécanisme d infection a été confirmé par l utilisation d un inhibiteur du transport d influx. Par ailleurs, le gène CgAUX1 est exprimé dans le primordium de racine latérale mais pas dans le primordium nodulaire. Cela suggère que ces deux organes présentent des différences dans leur programme de développement. Afin d identifier les mécanismes agissant en aval du transport d influx d auxine, nous avons étudié le rôle d AtLAX3 chez Arabidopsis. Nous avons montré qu un certain nombre de gènes de remodelage de la paroi sont induits par l auxine de façon dépendante d AtLAX3 au cours de l émergence de la racine latérale. Nous avons cherché à identifier des gènes de remodelage de la paroi qui pourraient être impliqués dans l infection par la bactérie Frankia de façon dépendante de CgAUX1. Cg12 qui code une protéase de type subtilisine spécifiquement exprimée dans les cellules infectées pourrait être une cible de la signalisation auxinique dépendante de CgAUX1. Nos résultats suggèrent que le transport d influx d auxine est impliqué dans la mise en place du nodule actinorhizien chez C. glaucaActinorhizal plants belonging to 8 families of angiosperms can enter symbiosis with a soil actinomycete called Frankia. This interaction leads to the formation of nitrogen fixing nodules on the plant root system. The actinorhizal nodule is considered as a modified lateral root because i) it originates from divisions of pericycle cells situated in front of xylem poles, ii) its vasculature is central and its growth is indeterminate due to the presence of an apical meristem and iii) in some species such as Casuarina glauca a so-called nodular root is formed at the apex of each nodule lobe. Auxin, and more particularly auxin influx, is involved in lateral root formation. We identified auxin influx transporter genes in the actinorhizal plant C. glauca and studied the role of auxin influx transport during actinorhizal nodule formation. Two AUX-LAX genes encoding for auxin influx carriers have been identified in C. glauca. The expression patterns of CgAUX1 and CgLAX3 are highly conserved between C. glauca and Arabidopsis thaliana. Functional complementation of the Arabidopsis aux1 mutant revealed that CgAUX1 and AtAUX1 share equivalent functions. Our data suggest that functional divergence exists in the AUX-LAX family. We analysed the role of these genes during the actinorhizal symbiosis. Expression studies showed that CgAUX1 is expressed in all infected cells. Moreover, we confirmed that auxin influx transport is involved in the symbiotic process by taking advantage of an auxin influx transport inhibitor. We also observed that CgAUX1 is expressed in lateral root primordium but not in nodule primordium thus pinpointing some differences in the developmental program of these two organs. We then tried to identify the mechanisms acting downstream of auxin influx transport by studying the role of AtLAX3 in Arabidopsis. We showed that a set of cell wall remodeling genes are induced by auxin in a AtLAX3 dependent way during lateral root emergence. We next tried to identify cell wall remodeling genes that could be involved in the infection process in a CgAUX1 dependent way. Cg12 encodes for a subtilisin-like protease that is specifically expressed in Frankia infected cells and could be a target of CgAUX1 dependent auxin signaling. Our results suggest that auxin influx transport is involved in the infection process during actinorhizal nodule formation in C. glaucaMONTPELLIER-BU Sciences (341722106) / SudocSudocFranceF

Recherche en ligne pour les Processus Décisionnels de Markov (application à la maintenance d'une constellation de satellites)

TOULOUSE-ENSEEIHT (315552331) / SudocSudocFranceF

Root Architecture Responses: In Search of Phosphate

International audienc

Genome Sequence Of White Lupin, A Model To Study Root Developmental Adaptations

International audienc

Correlations between gaseous and liquid phase chemistries induced by cold atmospheric plasmas in a physiological buffer

International audienceThe understanding of plasma–liquid interactions is of major importance, not only in physical chemistry, chemical engineering and polymer science, but in biomedicine as well as to better control the biological processes induced on/in biological samples by Cold Atmospheric Plasmas (CAPs). Moreover, plasma–air interactions have to be particularly considered since these CAPs propagate in the ambient air. Herein, we developed a helium-based CAP setup equipped with a shielding-gas device, which allows the control of plasma–air interactions. Thanks to this device, we obtained specific diffuse CAPs, with the ability to propagate along several centimetres in the ambient air at atmospheric pressure. Optical Emission Spectroscopy (OES) measurements were performed on these CAPs during their interaction with a liquid medium (phosphate-buffered saline PBS 10 mM, pH 7.4) giving valuable information about the induced chemistry as a function of the shielding gas composition (variable O2/(O2 + N2) ratio). Several excited species were detected including N2+(First Negative System, FNS), N2(Second Positive System, SPS) and HO˙ radical. The ratios between nitrogen/oxygen excited species strongly depend on the O2/(O2 + N2) ratio. The liquid chemistry developed after CAP treatment was investigated by combining electrochemical and UV-visible absorption spectroscopy methods. We detected and quantified stable oxygen and nitrogen species (H2O2, NO2−, NO3−) along with Reactive Nitrogen Species (RNS) such as the peroxynitrite anion ONOO−. It appears that the RNS/ROS (Reactive Oxygen Species) ratio in the treated liquid depends also on the shielding gas composition. Eventually, the composition of the surrounding environment of CAPs seems to be crucial for the induced plasma chemistry and consequently, for the liquid chemistry. All these results demonstrate clearly that for physical, chemical and biomedical applications, which are usually achieved in ambient air environments, it is necessary to realize an effective control of plasma–air interactions