Phase change-related variations of dome shape in Eucalyptus urophylla x Eucalyptus grandis shoot apical meristems

International audienceShoot apical meristem (SAM) domes derived from five different outdoor and in vitro sources of juvenile and mature Eucalyptus urophylla x Eucalyptus grandis akin genotypes were compared. Overall measurements of SAM dome height H and diameter D ranged from 2 to 35 µm and 20 to 80 µm, notwithstanding significant differences according to the various physiological origins of plant material investigated. SAM domes from the mature trees ?Mat? were taller than those from the rejuvenated ministock plants ?Rej?; from the in vitro microcuttings ?IVM? of the same clone, and also from the in vitro juvenile seedlings ?IVJ?, whereas outdoor seedlings ?Juv? SAM domes exhibited intermediate height. SAM domes from the rejuvenated material ?Rej?, from the in vitro mature ?IVM? and juvenile ?IVJ? origins were also narrower than those from the outdoor seedlings ?Juv? and to lesser extent than those from the mature trees ?Mat?. Overall the mature source ?Mat? displayed bigger and somehow sharper hemispherical domes than those from ?Rej? and ?Juv?, physiologically more juvenile, or those from the in vitro origins ?IVM ? and ?IVJ? which looked flatter and smaller. SAM dome height, diameter D and H/D values varied also significantly according to shoot apex status. More specifically, H, D and H/D SAM differences between the five origins were not significant when SAM were in their more organogenic stage, to become more salient as leaf structures started to elongate and to differentiate. This was particularly obvious for mature tree ?Mat? SAM dome shapes which showed at this stage much higher H/D values than the other SAM sources. Additionally, a shape index S used for characterizing more accurately dome shape confirmed these trends. These observations provide additional arguments to the view that juvenility in trees become more and more time and space restricted as ageing increases in the course of time during the ontogenetical process, to be ultimately confined to the more organogenic phases of SAM, from which shoot characteristics derive

Transcriptional induction of cell wall remodelling genes is coupled to microtubule-driven growth isotropy at the shoot apex in Arabidopsis

The shoot apical meristem of higher plants continuously generates new tissues and organs through complex changes in growth rates and directions of its individual cells. Cell growth, which is driven by turgor pressure, largely depends on the cell walls, which allow cell expansion through synthesis and structural changes. A previous study revealed a major contribution of wall isotropy in organ emergence, through the disorganization of cortical microtubules. We show here that this disorganization is coupled with the transcriptional control of genes involved in wall remodelling. Some of these genes are induced when microtubules are disorganized and cells shift to isotropic growth. Mechanical modelling shows that this coupling has the potential to compensate for reduced cell expansion rates induced by the shift to isotropic growth. Reciprocally, cell wall loosening induced by different treatments or altered cell wall composition promotes a disruption of microtubule alignment. Our data thus indicate the existence of a regulatory module activated during organ outgrowth, linking microtubule arrangements to cell wall remodelling

Characteristics of Acacia mangium shoot apical meristems in natural and in vitro conditions in relation to heteroblasty

PDF version of the authors can be published in January 2013International audienceMorphological and histocytological characteristics of Acacia mangium shoot apical meristems (SAMs) were assessed in natural and in vitro conditions in relation to heteroblasty. In the natural environment, SAMs with a mature-phyllode morphology were much bigger, contained more cells with larger vacuolated area, or vacuome, and lower nucleoplasmic ratios than those from the juvenile type (Juv). In these latter, nuclei appeared more voluminous, evenly and lightly stained, with clearly distinguishable nucleolei and less abundant chromocenters. In vitro, where reversions from mature to juvenile morphological traits do occur unpredictably, heteroblasty was less obvious in the SAM characteristics examined. In vitro SAMs corresponding to the juvenile and mature types showed similarities with outdoor Juv SAMs, but could be distinguished from these latter by a much larger vacuome that might be induced by the culture conditions. These findings encourage pursuing the investigations at the chromatin and nucleolus level in SAM zones where heteroblasty-related differences have been detected

Monitoring of proteobacteria and phytoplasma in sugar beets naturally or experimentally affected by the disease syndrome 'Basses richesses'

International audienceThe disease syndrome ‘Basses Richesses’(SBR) affects sugar beet (Beta vulgaris) crops and causes important economic damage in eastern France. Up to now two phloem-restricted prokaryotes which cannot be cultivated, a stolbur phytoplasma and a c-3 proteobacterium (called SBR proteobacterium), have been associated with the disease. The SBR proteobacterium is closely related to endosymbionts of Hemiptera in the genus Arsenophonus. Both the phytoplasma and the proteobacterium are transmitted by the insect vector Pentastiridius sp. (Hemiptera: Cixiidae). In the present work, we developed sensitive PCR tools for routine detection of SBR proteobacteria in sugar beets. The monitoring with PCR since 1997, of both SBR pathogen agents, showed the predominant aetiological role of SBR proteobacteria in SBR disease. Detection of SBR proteobacteria in sugar beet was correlated with development of SBR symptoms and reduction of sugar content in the taproot. Severity of symptoms and sugar content in experimentally inoculated sugar beet plants were a function of the number of Pentastiridius sp. used for transmission or the length of inoculation access period (IAP), suggesting a direct relationship between importance or precocity of populations of inoculative insects in fields and low sugar yield of crops

Bio-inspired Topological Skeleton for the Analysis of Quadruped Kinematic Gait

International audienceIn bio-inspired design activities, Nature is a basis of knowledge. Over the last twenty years, many solutions to measure and analyze human or animal gaits have been developed (VICON system, X-ray radiography...). Although, these methods are becoming more and more accurate, they are quite expensive, long to set up and not easily portable. In this paper, a method called the bio-inspired topological skeleton is suggested in order to complement the classic videography process and to enable animal gait analysis. A new predictive kin-ematic model with closed-loops of an unguligrade quadruped will be suggested. This kinematic model includes three segments per leg and takes into account the scapula movements. The proposed method allows us to improve the accuracy of the kinematic input data measured from a single video including an additional artefact. To show the benefits of this method, joint parameters that are difficult to measure are derived symbolically from a kinematic model and compared with experimental data

MaCS4Plants:A Mathematic & Computer Science Network for FSPM

International audienceSince the early 90’s, AMAP lab (Montpellier, France) has developed multiple softwareapplied to plant architecture modelling. More recently, AGAP Institute developed the OpenAleaplatform (Pradal et al., 2008) to answer the growing need for computational resourcescoming from the increasing complexity and scale of applications of plant models, and fordata analysis associated to new data acquisition techniques such as high-frequencyphenotyping platforms or LIDAR measurements. Both AMAPstudio and OpenAlea aredesigned for providing modelling tools for the FSPM community, they share commonformalisms for plant representation (i.e., MultiScaleTreeGraph, mtg; Godin et Caraglio,1998) and similar 3D edition and visualization tools. However, these tools have largelydiverged for multiple reasons: language source code, integration in different platforms,plants with different architectures studied for specific research topics but also differentlaboratories with distinct needs and directives. In this context, researchers and engineers specialized in mathematics and computer sciencefrom AMAP and AGAP decided to gather their expertise into the Mathematics & ComputerScience (CS) network For multiscale functional structural modelling of Plants within theiragroecological systems (MaCS4Plants). This network aims at providing an extensive libraryof generic functional models as well as tackling scientific problems in the math and CS domain applied toagroecological transition and resilience to climate change: big data analysis, hybridmodelling, multiscale and structure-function studies or full plant modelling (i.e., root andshoot). In this study, we will present the first achievements of the MaCS4Plants network:- An extensive catalogue of modelling software developed and their integration intoOpenAlea (https://openalea.rtfd.io).- The proposal of a standard format that integrates both topology and geometry atmultiscale of plants, and the possibility to export it toward common 3D visualizationsoftware.- A set of online didactic interactive notebooks on FSPM

Design, synthesis, and biological evaluation of novel selective peptide inhibitors of 11β-hydroxysteroid dehydrogenase 1

The enzyme 11β-HSD1 plays a crucial role in the tissue-specific regulation of cortisol levels and it has been associated with various diseases. Inhibition of 11β-HSD1 is an attractive intervention strategy and the discovery of novel selective 11β-HSD1 inhibitors is of high relevance. In this study, we identified and evaluated a new series of selective peptide 11β-HSD1 inhibitors with potential for skin care applications. This novel scaffold was designed with the aid of molecular modeling and two previously reported inhibitors. SAR optimization yielded highly active peptides (IC; 50; below 400 nM) that were inactive at 1 µM concentration against structurally related enzymes (11β-HSD2, 17β-HSD1 and 17β-HSD2). The best performing peptides inhibited the conversion of cortisone into cortisol in primary human keratinocytes and the most active compound, 5d, was further shown to reverse cortisone-induced collagen damage in human ex-vivo tissue

Canker stain of plane tree : last advances in genetical improvement for resistance

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