Nutrient uptake and growth of in vitro coconut (Cocos nucifera L.) calluses

La croissance #in vitro$ de deux lignées de cals de cocotier, L1 et L7, et l'évolution de la concentration des minéraux et des sucres dans les milieux de culture sont mesurés après 0, 14, 28, 42 et 56 jours de culture. Un contrôle histologique est réalisé aux jours 0, 28 et 56. Bien que les deux lignées soient multipliées sur des teneurs en 2,4-D différentes, la croissance (Poids de Matière Sèche) des deux lignées est identique et est liée à des besoins en éléments nutritifs équivalents. L'organisation de la zone méristématique des cals des deux lignées est très différente mais n'a pas d'influence sur leur nutrition. L'absorption des ions NH4, Ca et Mg est continue pendant tout le cycle de culture. Le saccharose et l'ion SO4 sont absorbés pendant la phase de latence et au début de la phase exponentielle de croissance. L'absorption des ions H2PO4 et NO3 apparaît seulement pendant la seconde moitié de la phase exponentielle. L'équilibre ionique est maintenu par les ions K et Cl. (Résumé d'auteur

Non PCR-amplified Transcripts and AFLP fragments as reduced representations of the quail genome for 454 Titanium sequencing

<p>Abstract</p> <p>Background</p> <p>SNP (Single Nucleotide Polymorphism) discovery is now routinely performed using high-throughput sequencing of reduced representation libraries. Our objective was to adapt 454 GS FLX based sequencing methodologies in order to obtain the largest possible dataset from two reduced representations libraries, produced by AFLP (Amplified Fragment Length Polymorphism) for genomic DNA, and EST (Expressed Sequence Tag) for the transcribed fraction of the genome.</p> <p>Findings</p> <p>The expressed fraction was obtained by preparing cDNA libraries without PCR amplification from quail embryo and brain. To optimize the information content for SNP analyses, libraries were prepared from individuals selected in three quail lines and each individual in the AFLP library was tagged. Sequencing runs produced 399,189 sequence reads from cDNA and 373,484 from genomic fragments, covering close to 250 Mb of sequence in total.</p> <p>Conclusions</p> <p>Both methods used to obtain reduced representations for high-throughput sequencing were successful after several improvements.</p> <p>The protocols may be used for several sequencing applications, such as <it>de novo </it>sequencing, tagged PCR fragments or long fragment sequencing of cDNA.</p

The Cyst-Dividing Bacterium Ramlibacter tataouinensis TTB310 Genome Reveals a Well-Stocked Toolbox for Adaptation to a Desert Environment

Ramlibacter tataouinensis TTB310T (strain TTB310), a betaproteobacterium isolated from a semi-arid region of South Tunisia (Tataouine), is characterized by the presence of both spherical and rod-shaped cells in pure culture. Cell division of strain TTB310 occurs by the binary fission of spherical “cyst-like” cells (“cyst-cyst” division). The rod-shaped cells formed at the periphery of a colony (consisting mainly of cysts) are highly motile and colonize a new environment, where they form a new colony by reversion to cyst-like cells. This unique cell cycle of strain TTB310, with desiccation tolerant cyst-like cells capable of division and desiccation sensitive motile rods capable of dissemination, appears to be a novel adaptation for life in a hot and dry desert environment. In order to gain insights into strain TTB310's underlying genetic repertoire and possible mechanisms responsible for its unusual lifestyle, the genome of strain TTB310 was completely sequenced and subsequently annotated. The complete genome consists of a single circular chromosome of 4,070,194 bp with an average G+C content of 70.0%, the highest among the Betaproteobacteria sequenced to date, with total of 3,899 predicted coding sequences covering 92% of the genome. We found that strain TTB310 has developed a highly complex network of two-component systems, which may utilize responses to light and perhaps a rudimentary circadian hourglass to anticipate water availability at the dew time in the middle/end of the desert winter nights and thus direct the growth window to cyclic water availability times. Other interesting features of the strain TTB310 genome that appear to be important for desiccation tolerance, including intermediary metabolism compounds such as trehalose or polyhydroxyalkanoate, and signal transduction pathways, are presented and discussed

Art et transmission. L'atelier du XIXe au XXIe siècle

International audienc

Imaging of the interface between fibers and matrix in the yarns of three-directional carbon-carbon composites by a photoacoustic method

International audienceThe performance of composite materials such as three-directional carbon-carbon composites depends greatly on the quality of the interface between the fibers and the matrix in the yarns. A set-up was built to examine the quality of this interface using a thermal method: photoacoustic method by photodeformation. Comparison of photoacoustic and electron beam microscope images, on the same area of a sample confirms that fibers 5 to 7 µm in diameter can be seen with the set-up. Moreover, the thermal phase images show discrepancies around some fibers which could be due to abnormal local thermal resistances

The dynamic protein partnership of RNA polymerase in <em>Bacillus subtilis</em>

National audienc