Rice auxin influx carrier OsAUX1 facilitates root hair elongation in response to low external phosphate

Root traits such as root angle and hair length influence resource acquisition particularly for immobile nutrients like phosphorus (P). Here, we attempted to modify root angle in rice by disrupting the OsAUX1 auxin influx transporter gene in an effort to improve rice P acquisition efficiency. We show by X-ray microCT imaging that root angle is altered in the osaux1 mutant, causing preferential foraging in the top soil where P normally accumulates, yet surprisingly, P acquisition efficiency does not improve. Through closer investigation, we reveal that OsAUX1 also promotes root hair elongation in response to P limitation. Reporter studies reveal that auxin response increases in the root hair zone in low P environments. We demonstrate that OsAUX1 functions to mobilize auxin from the root apex to the differentiation zone where this signal promotes hair elongation when roots encounter low external P. We conclude that auxin and OsAUX1 play key roles in promoting root foraging for P in rice

Increase Human Metapneumovirus Mediated Morbidity following Pandemic Influenza Infection

Human metapneumovirus (hMPV) is a recently discovered respiratory pathogen, infecting mainly young children. The infected patients suffer from influenza like symptoms (ILS). In Israel the virus is mainly circulating in February to March. Here we report on an increased rate of hMPV infection in the winter season of 2009–10. The 2009–10 infection had several unique characteristics when compared to previous seasons; it started around January and a large number of infants were infected by the virus. Genetic analysis based on the viral L and F genes of hMPV showed that only subtypes A2 and B2 circulated in Israel. Additionally, we have identified a novel variant of hMPV within subgroup A2b, which subdivide it into A2b1 and A2b2. Finally, we showed that the hMPV infection was detected in the country soon after the infection with the pandemic influenza virus had declined, that infection with the pandemic influenza virus was dominant and that it interfered with the infection of other respiratory viruses. Thus, we suggest that the unusual increase in hMPV infection observed in 2009–10 was due to the appearance of the pandemic influenza virus in the winter season prior to 2009–10

Lasso mutants link root gravitropic response and salt stress

Lasso mutants link root gravitropic response and salt stress. 8th International Symposium on Root Developmen

Lasso mutants link root gravitropic response and salt stress

Lasso mutants link root gravitropic response and salt stress. 8th International Symposium on Root Developmen

Unravelling cluster root development in white lupin

Unravelling cluster root development in white lupin. Unravelling cluster root development in white lupi

Développement et Plasticité du Système Racinaire : étude du lupin blanc

International audienc

Unravelling cluster root development in white lupin

Unravelling cluster root development in white lupin. Unravelling cluster root development in white lupi

Unravelling cluster root development in white lupin

International audienc

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