Recent emergence and worldwide spread of the red tomato spider mite, [i]Tetranychus evansi[/i]: genetic variation and multiple cryptic invasions

Publication Inra prise en compte dans l'analyse bibliométrique des publications scientifiques mondiales sur les Fruits, les Légumes et la Pomme de terre. Période 2000-2012. http://prodinra.inra.fr/record/256699Plant biosecurity is increasingly challenged by emerging crop pests. The spider mite Tetranychus evansi has recently emerged as a new threat to solanaceous crops in Africa and the Mediterranean basin, with invasions characterized by a high reproductive output and an ability to withstand a wide range of temperatures. Mitochondrial (868 bp of COI) and nuclear (1,137 bp of ITS) loci were analyzed in T. evansi samples spanning the current geographical distribution to study the earliest stages of the invasive process. The two sets of markers separate the samples into two main clades that are only present together in South America and Southern Europe. The highest COI diversity was found in South America, consistent with the hypothesis of a South American origin of T. evansi. Among the invaded areas, the Mediterranean region displayed a high level of genetic diversity similar to that present in South America, that is likely the result of multiple colonization events. The invasions of Africa and Asia by T. evansi are characterized by a low genetic variation associated with distinct introductions. Genetic data demonstrate two different patterns of invasions: (1) populations in the Mediterranean basin that are a result of multiple cryptic introductions and (2) emerging invasions of Africa and Asia, each likely the result of propagules from one or limited sources. The recent invasions of T. evansi illustrate not only the importance of human activities in the spread of agricultural pests, but also the limits of international quarantine procedures, particularly for cryptic invasion

AFM and Microrheology in the Zebrafish Embryo Yolk Cell

Elucidating the factors that direct the spatio-temporal organization of evolving tissues is one of the primary purposes in the study of development. Various propositions claim to have been important contributions to the understanding of the mechanical properties of cells and tissues in their spatiotemporal organization in different developmental and morphogenetic processes. However, due to the lack of reliable and accessible tools to measure material properties and tensional parameters in vivo, validating these hypotheses has been difficult. Here we present methods employing atomic force microscopy (AFM) and particle tracking with the aim of quantifying the mechanical properties of the intact zebrafish embryo yolk cell during epiboly. Epiboly is an early conserved developmental process whose study is facilitated by the transparency of the embryo. These methods are simple to implement, reliable, and widely applicable since they overcome intrusive interventions that could affect tissue mechanics. A simple strategy was applied for the mounting of specimens, AFM recording, and nanoparticle injections and tracking. This approach makes these methods easily adaptable to other developmental times or organisms

A Fast and Efficient Decellularization Method for Tissue Slices

The study and use of decellularized extracellular matrix (dECM) in tissue engineering, regenerative medicine, and pathophysiology have become more prevalent in recent years. To obtain dECM, numerous decellularization procedures have been developed for the entire organ or tissue blocks, employing either perfusion of decellularizing agents through the tissue's vessels or submersion of large sections in decellularizing solutions. However, none of these protocols are suitable for thin tissue slices (less than 100 μm) or allow side-by-side analysis of native and dECM consecutive tissue slices. Here, we present a detailed protocol to decellularize tissue sections while maintaining the sample attached to a glass slide. This protocol consists of consecutive washes and incubations of simple decellularizing agents: ultrapure water, sodium deoxycholate (SD) 2%, and deoxyribonuclease I solution 0.3 mg/mL (DNase I). This novel method has been optimized for a faster decellularization time (2-3 h) and a better correlation between dECM properties and native tissue-specific biomarkers, and has been tested in different types of tissues and species, obtaining similar results. Furthermore, this method can be used for scarce and valuable samples such as clinical biopsies

Thrombin-induced contraction in alveolar epithelial cells probed by traction microscopy

Contractile tension of alveolar epithelial cells plays a major role in the force balance that regulates the structural integrity of the alveolar barrier. The aim of this work was to study thrombin-induced contractile forces of alveolar epithelial cells. A549 alveolar epithelial cells were challenged with thrombin, and time course of contractile forces was measured by traction microscopy. The cells exhibited basal contraction with total force magnitude 55.0 ± 12.0 nN (mean ± SE, n = 12). Traction forces were exerted predominantly at the cell periphery and pointed to the cell center. Thrombin (1 U/ml) induced a fast and sustained 2.5-fold increase in traction forces, which maintained peripheral and centripetal distribution. Actin fluorescent staining revealed F-actin polymerization and enhancement of peripheral actin rim. Disruption of actin cytoskeleton with cytochalasin D (5 µM, 30 min) and inhibition of myosin light chain kinase with ML-7 (10 µM, 30 min) and Rho kinase with Y-27632 (10 µM, 30 min) markedly depressed basal contractile tone and abolished thrombin-induced cell contraction. Therefore, the contractile response of alveolar epithelial cells to the inflammatory agonist thrombin was mediated by actin cytoskeleton remodeling and actomyosin activation through myosin light chain kinase and Rho kinase signaling pathways. Thrombin-induced contractile tension might further impair alveolar epithelial barrier integrity in the injured lung

Effects of two different decellularization routes on the mechanical properties of decellularized lungs

Considering the limited number of available lung donors, lung bioengineering using whole lung scaffolds has been proposed as an alternative approach to obtain lungs suitable for transplantation. However, some decellularization protocols can cause alterations on the structure, composition, or mechanical properties of the lung extracellular matrix. Therefore, the aim of this study was to compare the acellular lung mechanical properties when using two different routes through the trachea and pulmonary artery for the decellularization process. This study was performed by using the lungs excised from 30 healthy male C57BL/6 mice, which were divided into 3 groups: tracheal decellularization (TDG), perfusion decellularization (PDG), and control groups (CG). Both decellularized groups were subjected to decellularization protocol with a solution of 1% sodium dodecyl sulfate. The behaviour of mechanical properties of the acellular lungs was measured after decellularization process. Static (Est) and dynamic (Edyn) elastances were obtained by the end-inspiratory occlusion method. TDG and PDG showed reduced Est and Edyn elastances after lung decellularization. Scanning electron microscopy showed no structural changes after lung decellularization of the TDG and PDG. In conclusion, was demonstrated that there is no significant difference in the behaviour of mechanical properties and extracellular matrix of the decellularized lungs by using two different routes through the trachea and pulmonary artery

Alzheimer's disease mutant mice exhibit reduced brain tissue stiffness compared to wild-type mice in both normoxia and following intermittent hypoxia mimicking sleep apnea

Background: Evidence from patients and animal models suggests that obstructive sleep apnea (OSA) may increase the risk of Alzheimer's disease (AD) and that AD is associated with reduced brain tissue stiffness.Aim: To investigate whether intermittent hypoxia (IH) alters brain cortex tissue stiffness in AD mutant mice exposed to IH mimicking OSA.Methods: Six-eight month old (B6C3-Tg(APPswe, PSEN1dE9)85Dbo/J) AD mutant mice and wild-type (WT) littermates were subjected to IH (21% O-2 40 s to 5% O-2 20 s; 6 h/day) or normoxia for 8 weeks. After euthanasia, the stiffness (E) of 200-mu m brain cortex slices was measured by atomic force microscopy.Results: Two-way ANOVA indicated significant cortical softening and weight increase in AD mice compared to WT littermates, but no significant effects of IH on cortical stiffness and weight were detected. In addition, reduced myelin was apparent in AD (vs. WT), but no significant differences emerged in the cortex extracellular matrix components laminin and glycosaminoglycans when comparing baseline AD and WT mice.Conclusion: AD mutant mice exhibit reduced brain tissue stiffness following both normoxia and IH mimicking sleep apnea, and such differences are commensurate with increased edema and demyelination in AD

Pest categorisation of Longidorus diadecturus

The Panel on Plant Health performed a pest categorisation of Longidorus diadecturus (Nematoda: Longidoridae) for the EU. The nematode is a well-defined taxon and was described from Ontario, Canada and later reported from some states in the USA. The nematode is not present in the EU. It is regulated by Council Directive 2000/29/EC, listed in Annex I A I as L. diadecturus Eveleigh and Allen. It is a migratory ectoparasitic nematode species puncturing cells of plant roots thereby able to transmit the nepovirus Peach rosette mosaic virus (PRMV). The pest is found in soil associated with plant species belonging to different families. L. diadecturus is able to cause direct damage to plants, but its main damage is caused by vectoring PRMV. Soil is a potential pathway for this nematode for entry into the EU. The nematode is able to survive adverse conditions, but the virus may not persist inside the nematode for extended periods. Climatic conditions in the EU are similar to those found in the countries where the pest is currently present. Hosts of the nematode (and the associated virus) are, e.g. peaches and grapes; those crops are also widely cultivated in the EU. The nematode only moves short distances (around 1 m) but may be spread with soil moving activities. Measures are available to inhibit entry via soil as such. Entry of the nematode with soil attached to plants for planting that are not regulated is possible. L. diadecturus does satisfy all the criteria that are within the remit of EFSA to assess to be regarded as a potential Union quarantine pest

Vitis sp. response to Xylella fastidiosa strain CoDiRO

Following a request from the European Commission, the EFSA Panel on Plant Health assessed a scientific report submitted by the Italian Authorities to the European Commission to support a request to delist Vitissp. from Annex I (‘specified plants’) of the Commission Implementing Decision (EU) 2015/789 of 18 May 2015 to prevent the introduction into and the spread within the Union of Xylella fastidiosa (Wells et al.). The report comprised (i) surveys to detect X. fastidiosa in vineyards located in the epidemic zone of CoDiRO with high numbers of diseased olive trees; (ii) inoculation experiments to infect grapevine with a X. fastidiosa isolate ‘De Donno’ from CoDiRO diseased olives; and (iii) vector transmission experiments with X. fastidiosa infective Philaenus spumarius. The Panel acknowledges the difficulties in providing evidence about this hitherto unknown pathogen/vector/host interaction to support the hypothesis that a plant species cannot be infected with a pathogen. Although field surveys to detect X. fastidiosa in grapevine were negative, there was no supporting information on infective vector populations present in the vineyards. Hence absence of infection pressure cannot be excluded. Furthermore the failure to infect grapevine plants either by artificial inoculation or by vector transmission might be due to inoculation conditions not appropriate to induce infections in grapevine. The detection of X. fastidiosa DNA in inoculated grapevine plants even 12 months after inoculation, although localised at the inoculation points, cannot exclude that the DNA amplified by qPCR was from viable cells. The results presented are coherent and provide converging lines of evidence that grapevine (Vitis vinifera) is not a major susceptible host of X. fastidiosa strain CoDiRO. However, from the experimental evidence it is premature to exclude that systemic infections of V.vinifera and Vitissp. occur and that infections at limited foci could serve as a source of inoculum

Pest categorisation of Scirtothrips citri

The Panel on Plant Health performed a pest categorisation of the citrus thrips, Scirtothrips citri (Moulton) (Thysanoptera: Thripidae), for the European Union (EU). This is a well-de fi ned and distinguishable species, occurring in North America and Asia. Its precise distribution in Asia is uncertain. S. citri is a pest of citrus and blueberries and has been cited on over 50 different host species in 33 plant families. Whether all plants reported as hosts are true hosts, allowing population development of S. citri , is uncertain. S. citri feeds exclusively on young actively growing foliage and fruit. It is not known to occur in the EU and is listed in Annex IIAI of 2000/29/EC as a harmful organism. The international trade of hosts, as either plants for planting or cut fl owers, provide potential pathways into the EU. However, current EU legislation prohibits the import of citrus plants for planting. Furthermore, measures aimed at the import of plants for planting in a dormant stage (no young foliage or fruits present) with no soil/growing medium attached, decreases the likelihood of the pest ’ s entry via other hosts. Considering that there are regional climatic similarities where S. citri occurs in the USA with climates in the EU, and taking EU host distribution into account, S. citri has the potential to establish in the EU, especially in citrus and blueberry growing regions around the Mediterranean where quality losses in citrus and yield losses in blueberry could occur. Phytosanitary measures are available to inhibit the likelihood of introduction of S. citri from infested countries. Considering the criteria within the remit of EFSA to assess its status as a potential Union quarantine pest (QP) or as a potential regulated non-quarantine pest (RNQP), S. citri meets with no uncertainties the criteria assessed by EFSA for consideration as a potential Union QP

Hot water treatment of Vitis sp. for Xylella fastidiosa

Following a request from the European Commission, the EFSA Panel on Plant Health (PLH) reviewed Italian technical guidelines and the ANSES (Agence nationale de sécurité sanitaire de l’alimentation, de l’environnement et du travail) opinion on the use of hot water treatment (HWT) on Vitis sp. planting material, assessing its efficacy in the elimination of the xylem-invading bacterial pathogen, Xylella fastidiosa. HWT is a robust and reliable technique used to destroy life stages of pests (insects, nematodes) and to inactivate pathogens (phytoplasma, bacteria, fungi) in dormant plant propagation materials (grapevine and other crops). An effective HWT sanitizes the planting material without affecting plant survival and development. For grapevine, HWT to eliminate the Grapevine flavescence dorée phytoplasma (FD) from planting materials is among the special requirements for the introduction and movement of Vitis sp. to protected zones in the EU. The conditions of 50°C for 45 min, prescribed and recommended to sanitize grapevine planting material against FD, are considered by the Panel to be also effective against X. fastidiosa and its subspecies. Despite uncertainties on variable thermotolerances of the bacteria, a HWT treatment of 50°C for 45 minutes can effectively account for different thermotolerances. It should be noted that the quality of the HWT is subject to the proper application of the operating procedures to guarantee vigorous growth and pathogen freedom of planting material