Dissection of the auxin response pathway using functional and chemical genetic approaches

Notably, the hormone regulates the formation and emergence of lateral roots (LRs). In Arabidopsis thaliana the initiation of lateral root primordia (LRP) is induced by auxin and takes place deep within the parental root. Also, the emergence of the LRP through the overlying tissues is regulated by auxin. It has been shown that the gene LAX3 is expressed in cortical and epidermal directly overlying a LRP. External auxin induces LAX3's expression in all cortical and epidermal cells suggesting that it actsas the activating signal. There are two objectives in this study: the first one is to understand how the expression of LAX3 is regulated and the second one is to identify and characterise novel inhibitors of the induction of LAX3. It has been shown that mutations in ARF7 and ARF19 or IAA14/SLR are sufficient to block LAX3 auxin induction. Using classical genetics approaches, it is shown that ARF7 and ARF19 actually regulate LAX3 positively and negatively, respectively. Furthermore, a canonical Auxin Response Element present in the promoter of LAX3 is shown to negatively regulate its expression. Using transcriptomics datasets, a regulatory network is proposed and several putative candidates have been selected. In order to obtain alternative approaches to dissect the induction of LAX3, a suite of 13 inhibitors (representing 8 distinct classes of compounds) have identified. The major and most promising class has been investigated and shown to interfere most probably with the E2 conjugating enzymes. A model and preliminary results with some of the other inhibitors identified are proposed

Dissection of the auxin response pathway using functional and chemical genetic approaches

Notably, the hormone regulates the formation and emergence of lateral roots (LRs). In Arabidopsis thaliana the initiation of lateral root primordia (LRP) is induced by auxin and takes place deep within the parental root. Also, the emergence of the LRP through the overlying tissues is regulated by auxin. It has been shown that the gene LAX3 is expressed in cortical and epidermal directly overlying a LRP. External auxin induces LAX3's expression in all cortical and epidermal cells suggesting that it actsas the activating signal. There are two objectives in this study: the first one is to understand how the expression of LAX3 is regulated and the second one is to identify and characterise novel inhibitors of the induction of LAX3. It has been shown that mutations in ARF7 and ARF19 or IAA14/SLR are sufficient to block LAX3 auxin induction. Using classical genetics approaches, it is shown that ARF7 and ARF19 actually regulate LAX3 positively and negatively, respectively. Furthermore, a canonical Auxin Response Element present in the promoter of LAX3 is shown to negatively regulate its expression. Using transcriptomics datasets, a regulatory network is proposed and several putative candidates have been selected. In order to obtain alternative approaches to dissect the induction of LAX3, a suite of 13 inhibitors (representing 8 distinct classes of compounds) have identified. The major and most promising class has been investigated and shown to interfere most probably with the E2 conjugating enzymes. A model and preliminary results with some of the other inhibitors identified are proposed

Contribution à la connaissance des Coléoptères saproxyliques des forêts pyrénéennes : 3ème note : la forêt de Hèches, Hautes-Pyrénées

L’amélioration de la connaissance des cortèges de Coléoptères saproxyliques présents dans les forêts gérées des Pyrénées est un préalable indispensable à leur conservation. Dans le cadre d’une étude menée sur la propriété du Groupement Forestier de Hèches, un inventaire des Coléoptères saproxyliques a été conduit en 2003 et 2004, au moyen de pièges et de chasse à vue. Une liste de 374 taxons (espèces non-saproxyliques incluses) a ainsi été établie. Quelques espèces rares, voire inattendues font l’objet de commentaires faunistiques. Cet inventaire offre par ailleurs l’opportunité de situer le massif forestier étudié dans une échelle de valeur biologique des forêts pyrénéennes en 5 classes

Transcriptional reprogramming during floral fate acquisition

Coordinating growth and patterning is essential for eukaryote morphogenesis. In plants, auxin is a key regulator of morphogenesis implicated throughout development. Despite this central role, our understanding of how auxin coordinates cell fate and growth changes is still limited. Here, we addressed this question using a combination of genomic screens to delve into the transcriptional network induced by auxin at the earliest stage of flower development, prior to morphological changes. We identify a shoot-specific network suggesting that auxin initiates growth through an antagonistic regulation of growth-promoting and growth-repressive hormones, quasi-synchronously to floral fate specification. We further identify two DNA-binding One Zinc Finger (DOF) transcription factors acting in an auxin-dependent network that could interface growth and cell fate from the early stages of flower development onward.Peer reviewe

Bat responses to changes in forest composition and prey abundance depend on landscape matrix and stand structure

Despite the key importance of the landscape matrix for bats, we still not fully understand how the effect of forest composition interacts at combined stand and landscape scales to shape bat communities. In addition, we lack detailed knowledge on the effects of local habitat structure on bat-prey relationships in forested landscapes. We tested the assumptions that (i) forest composition has interacting effects on bats between stand and landscape scales; and (ii) stand structure mediates prey abundance effects on bat activity. Our results indicated that in conifer-dominated landscapes (> 80% of coniferous forests) bat activity was higher in stands with a higher proportion of deciduous trees while bats were less active in stands with a higher proportion of deciduous trees in mixed forest landscapes (~ 50% of deciduous forests). Moth abundance was selected in the best models for six among nine bat species. The positive effect of moth abundance on Barbastella barbastellus was mediated by vegetation clutter, with dense understory cover likely reducing prey accessibility. Altogether, our findings deepen our understanding of the ecological processes affecting bats in forest landscapes and strengthen the need to consider both landscape context and trophic linkage when assessing the effects of stand-scale compositional and structural attributes on bats

Insights about saproxylic biodiversity living in old-growth forests of French Pyrénées

The symposium will span over four days, including a one day field trip. Keynote addresses will introduce morning sessions followed by parallel conference sessions. Scientific poster sessions, held in the late afternoon, will be combined with a cocktail buffet. A banquet will take place on Wednesday night. All events will be held at the Rouyn-Noranda Congress Center

Bois mort, micro-habitats et cie : Quels déterminants locaux pour les coléoptères saproxyliques

Bois mort, micro-habitats et cie : Quels déterminants locaux pour les coléoptères saproxylique

Connectivité spatiale et diversité des espèces: Mise en place d’un réseau de conservation dans le Parc National du Mercantour

La thématique des forêts anciennes et des forêts matures a été au cœur du séminaire physique du GT Forêt-Eau, avec l'organisation le 27 octobre 2015 d'une journée d'échanges et de visite, associant une douzaine de partenaires (INRA, IRSTEA, Purpan, RNF, FPNR, CBNMC...). Au delà, PNF [Parcs Nationaux de France] continuera à suivre les différents projets en cours, menés par des Parcs nationaux ou d'autres partenaires, et à envisager d'autres projets collectifs pour aller plus loin dans la connaissance des forêts anciennes et matures

Sequential induction of auxin efflux and influx carriers regulates lateral root emergence

Peer reviewe

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