Plant DNA polymerases

Maintenance of genome integrity is a key process in all organisms. DNA polymerases (Pols) are central players in this process as they are in charge of the faithful reproduction of the genetic information, as well as of DNA repair. Interestingly, all eukaryotes possess a large repertoire of polymerases. Three protein complexes, DNA Pol α, δ, and ε, are in charge of nuclear DNA replication. These enzymes have the fidelity and processivity required to replicate long DNA sequences, but DNA lesions can block their progression. Consequently, eukaryotic genomes also encode a variable number of specialized polymerases (between five and 16 depending on the organism) that are involved in the replication of damaged DNA, DNA repair, and organellar DNA replication. This diversity of enzymes likely stems from their ability to bypass specific types of lesions. In the past 10–15 years, our knowledge regarding plant DNA polymerases dramatically increased. In this review, we discuss these recent findings and compare acquired knowledge in plants to data obtained in other eukaryotes. We also discuss the emerging links between genome and epigenome replication

Electro-precipitation of magnetite nanoparticles: an electrochemical study

Nanoparticles of magnetites (Fe3O4) are synthesized with a new process based on electro-precipitation in ethanol medium. A mechanism pathway is proposed consisting of a Fe(OH)3 precipitation followed by the reduction of iron hydroxide to magnetite in the presence of hydroxyl ions which are enerated at the cathode

A Method for the Allotment of Maize Contaminated by Toxins

Deoxynivalenol and fumonisins pose a health concern and have economic consequences, so the European regulation CE 1126/2007 dictates the maximal content allowed in cereals. The direct measurement of mycotoxin content using the established method is not only time-consuming and tedious, but also destructive and cannot be used in a silo. Alternative tools such as infrared spectroscopy are therefore being studied. For the present investigation, spectral data collected from maize kernels contaminated naturally by mycotoxins were studied to predict the risk of deoxynivalenol and fumonisins. Discriminant models were used to create and identify batches that satisfy regulations for animal or human consumption

An infrared diagnostic system to detect causal agents of grapevine trunk diseases

In most vineyards worldwide, agents of grapevine trunk diseases represent a real threat for viticulture and are responsible for significant economic loss to the wine industry. The conventional microbiological isolation technique used to diagnose this disease is tedious and frequently leads to false negatives. Thus, a dire need exists for an alternative method to detect this disease. One possible way involves infrared spectroscopy, which is a rapid, nondestructive analytical tool that is commonly used for quality control of feed stuffs. In the present work, a midinfrared spectrometer was tested as a fast tool for detecting agents of grapevine trunk disease. Midinfrared spectra were collected from 70 Vitis vinifera L. cv. Cabernet-Sauvignon one year old trunk-wood samples that were infected naturally in one viticulture nursery of the south of France. The samples underwent polymerase chain reaction and morphological identification, and the results were correlated to the midinfrared spectra by using multivariate analysis to discriminate between noninfected and infected samples. Based on comparison with some control samples, the highest percentage of correct identification of fungal contamination when using the midinfrared spectroscopy method is 80%

Énergétique et régulation de la fonction de reproduction chez des femelles captives Babouins Olive (Papio anubis)

The aim of this study was to assess energetic and social parameters of lactating female baboons, and to test the possible role of these factors on different reproductive variables such as postpartum amenorrhea duration or interbirth intervals. A 2-year follow-up was carried out for a sample of 23 multiparous and semi-free living lactating female baboons. There were no rank-related differences in mean energy intakes among the females. All females were in good physical condition and had positive energy balance. The energy costs of lactation were primarily covered by 2 behavioural adaptations: moderate energy intakes increase, particularly during the second and third quarter of lactation, and physical activity decreases. Compared with free-living female baboons, reduced energetic constraints (adequate energy intakes and moderate energetic expenditure) explain short postpartum amenorrhea durations and interbirth intervals in our sample. Fertility is strongly influenced by dominance rank, low-ranking females having longer delays before conception and longer inter-birth intervals. Moreover, mothers with heavier infants have shorter postpartum amenorrhea durations and need fewer cycles to conceive. High-ranking females or those in good physical condition appear likely to withstand relatively rapid infant growth which is independent of the infant’s sex, and have therefore higher reproductive rates. It is unlikely that nutritional mechanisms alone affect the relationship between dominance status and fertility, and our results suggest rather that social stress would also interfere with regulation of reproductive function

How Herbivores Optimise Diet Quality and Intake in Heterogeneous Pastures, and the Consequences for Vegetation Dynamics

Understanding the interplay between foraging behaviour and vegetation dynamics in heterogeneous pasture is an essential requirement for evaluating the value of the resource for large herbivores and for managing that resource. The orientation of selective grazing behaviour between intake and diet quality depends on the spatial and temporal scales considered. In the short-term scale of a grazing sequence, there is evidence that large herbivores tend to optimise the intake rate of digestible materials by adaptation of their biting behaviour and by patch choice. On a day-to-day scale, there is evidence that large herbivores tend to prioritise the quality of the diet to minimise digestive constraints within the time that they can spend grazing. On a pasture scale, the search for areas giving the best trade-off between quantity and quality of intake leads to the optimisation of their foraging paths, in particular by modulating their sinuosity in response to heterogeneity. Repeated grazing of preferred patches creates a positive feedback on forage quality and enhances heterogeneity. Long-term consequences on vegetation dynamics, botanic composition and grassland quality are less understood

Updated Overview of Infrared Spectroscopy Methods for Detecting Mycotoxins on Cereals (Corn, Wheat, and Barley)

Each year, mycotoxins cause economic losses of several billion US dollars worldwide. Consequently, methods must be developed, for producers and cereal manufacturers, to detect these toxins and to comply with regulations. Chromatographic reference methods are time consuming and costly. Thus, alternative methods such as infrared spectroscopy are being increasingly developed to provide simple, rapid, and nondestructive methods to detect mycotoxins. This article reviews research conducted over the last eight years into the use of near-infrared and mid-infrared spectroscopy to monitor mycotoxins in corn, wheat, and barley. More specifically, we focus on the Fusarium species and on the main fusariotoxins of deoxynivalenol, zearalenone, and fumonisin B1 and B2. Quantification models are insufficiently precise to satisfy the legal requirements. Sorting models with cutoff levels are the most promising application

Stratégie de classement des lots de maïs en fonction de leurs teneurs en fusariotoxines par spectroscopie infrarouge

Dans le maïs, les teneurs maximales en déoxynivalénol (DON) et fumoni- sines (FUM) sont édictées par le règlement CE 1126/2007. La mesure directe de ces mycotoxines est un processus long et coûteux et n'est pas appropriée pour des mesures en flux. Une alternative a donc été développée avec l'ana- lyse infrarouge (IR). Le premier essai porte sur la discrimination des espèces de Fusarium par IR, sur milieu de culture. Nous avons démontré que cette discrimination est possible à 5 jours de culture pour F. graminearum, F. proliferatum, F. subglutinans et F. verticillioides. De plus, l'étude de la cinétique de crois- sance par IR nous a permis d'identifier 4 zones spectrales caractéristiques qui pourront éventuellement servir à un suivi en ligne. Lors du second essai, les modèles de classement des lots de maïs en fonction des teneurs en DON et FUM ont été préférés aux modèles de quanti- fication. En effet, ces derniers n'ont pas montré de performances suffisantes pour être utilisés en routine, bien que les approches SVM aient été très inté- ressantes. Les modèles de classement, qu'ils soient PLS, ANN ou SVM, ont permis d'isoler de grandes proportions de maïs sain du reste du lot. Enfin, un dernier essai a permis d'identifier deux limites au-delà des- quelles un échantillon de maïs a de fortes probabilités d'être contaminé en FUM : 200000 UFC/g de mycoflore totale et 3.5 ppm d'ergostérol. La combinaison de ces modèles devrait permettre un classement des lots de maïs pour le risque DON+FUM.The European regulation CE 1126/2007 dictates the maximal mycotoxins contents allowed in cereals. Their direct measurement with the reference methods is long and tedious. Furthermore, it is destructive and cannot be used at silo. Alternative tools such as infrared spectroscopy are studied. The objective of the first part of the study is to apply near infrared spectroscopy to identify and discriminate Fusarium isolates, grown on solid culture medium, without preparation of the sample. This approach should allow discrimination of Fusarium species most abundant in the corn : Fusarium graminearum, Fusarium proliferatum, Fusarium subglutinans, Fusarium verticillioides. The infrared spectra of 58 strains belonging to these four species were collected on a spectrometer. A model based on artificial neural networks was developed for the species discrimination. With this model, the correct classifiaction on the external validation set was very good (98.8%). The objective of the second part is to sort the corn samples regarding their deoxynivalenol and fumonisins contents. More than 2000 samples were used in this study. Their infrared spectra were collected on a near spectrometer, and they were referenced for their mycotoxins contents with chromatography methods. The performances of the infrared models developed to quantify the deoxynivalenol (DON) and the fumonisins (FUM) contents are not good enough to be used in the field, even if the support vector machines approach gives interesting results. Thus, qualitative models were developed to sort the samples in three classes : 'no risk for DON and FUM', 'risk for DON and/or FUM' and a middle class 'samples to be analysed by reference method'. The objective of the last part is to study the link between contents of ergosterol, fumonisins and fungal biomass (Colony Forming Units-CFU) in 117 corn sapmles. A fungal cell count was also done for 34 species. The near infared spectra of the corn samples were collected and used to predict the fungal biomass and the ergosterol contents