Nucleases are upregulated in potato tubers afflicted with zebra chip disease.

MAIN CONCLUSION: The defense response of potato tubers afflicted with zebra chip disease involves oxidatively mediated upregulation of nucleases that likely modulate localized programmed cell death to restrict the phloem-mobile, CLso bacterial pathogen to the vasculature. Zebra chip (ZC) is a bacterial disease of potato (Solanum tuberosum L.) caused by Candidatus Liberibacter solanacearum (CLso). Tubers from infected plants develop characteristic brown discoloration of the vasculature, a result of localized programmed cell death (PCD). We examined the potential contribution of nucleases in the response of tubers to CLso infection. Specific activities of the major isozymes of dsDNase, ssDNase, and RNase were substantially upregulated in tubers from CLso-infected plants, despite their significantly lower soluble protein content. However, ZC disease had no effect on nuclease isozyme profiles. Activities of the predominant nuclease isoforms from healthy and CLso-infected tubers had similar pH optima, thermotolerance, and responses to metallic co-factors. Nuclease activities were heat stable to 60 °C and resistant to precipitation with 70% (v/v) isopropanol, which constitute effective techniques for partial purification. DNase and RNase isozyme activities were highest at pH 7.2-8.5 and 6.8-7.2, respectively, and profiles were similar for tubers from CLso-infected and non-infected plants. RNase activities were mostly insensitive to inhibition by EDTA, except at pH 8.5 and above. DNase activities were inhibited by EDTA but less sensitive to inhibition at high pH than the RNases. The EDTA-mediated inhibition of DNase (ds/ss) activities was restored with ZnSO4, but not Ca+2 or Mg+2. By contrast, ZnSO4 inhibited the activities of RNases. DTT and CuSO4 inhibited the activities of all three nucleases. These results suggest that activation of tuber nucleases is dependent on the oxidation of sulfhydryl groups to disulfide and/or oxidation of Zn to Zn+2. In light of previous published results that established extensive CLso-induced upregulation of oxidative stress metabolism in tubers, we propose a model to show how increased nuclease activity could result from a glutathione-mediated oxidation of nuclease sulfhydryl groups in diseased tubers. DNases and RNases are likely an integral part of the hypersensitive response and may modulate PCD to isolate the pathogen to the vascular tissues of tubers.

An agenda for research and action toward diverse and just futures for life on Earth.

Decades of research and policy interventions on biodiversity have insufficiently addressed the dual issues of biodiversity degradation and social justice. New approaches are therefore needed. We devised a research and action agenda that calls for a collective task of revisiting biodiversity toward the goal of sustaining diverse and just futures for life on Earth. Revisiting biodiversity involves critically reflecting on past and present research, policy, and practice concerning biodiversity to inspire creative thinking about the future. The agenda was developed through a 2-year dialogue process that involved close to 300 experts from diverse disciplines and locations. This process was informed by social science insights that show biodiversity research and action is underpinned by choices about how problems are conceptualized. Recognizing knowledge, action, and ethics as inseparable, we synthesized a set of principles that help navigate the task of revisiting biodiversity. The agenda articulates 4 thematic areas for future research. First, researchers need to revisit biodiversity narratives by challenging conceptualizations that exclude diversity and entrench the separation of humans, cultures, economies, and societies from nature. Second, researchers should focus on the relationships between the Anthropocene, biodiversity, and culture by considering humanity and biodiversity as tied together in specific contexts. Third, researchers should focus on nature and economies by better accounting for the interacting structures of economic and financial systems as core drivers of biodiversity loss. Finally, researchers should enable transformative biodiversity research and action by reconfiguring relationships between human and nonhuman communities in and through science, policy, and practice. Revisiting biodiversity necessitates a renewed focus on dialogue among biodiversity communities and beyond that critically reflects on the past to channel research and action toward fostering just and diverse futures for human and nonhuman life on Earth.

Una Agenda para la Investigación y la Acción hacia un Futuro Diverso y Justo para la Vida sobre la Tierra Resumen Las décadas de investigación e intervenciones políticas sobre la biodiversidad han tratado significativamente los temas de la degradación de la biodiversidad y la justicia social. Debido a esto, se requieren nuevas estrategias. Diseñamos una agenda de investigación y acción que llama a la labor colectiva de revisar la biodiversidad hacia el objetivo de sustentar un futuro diverso y justo para la vida sobre la Tierra. Cuando se revisa la biodiversidad, se requiere de una reflexión crítica sobre las investigaciones, políticas y prácticas presentes y pasadas sobre la biodiversidad para inspirar un pensamiento creativo acerca del futuro. Desarrollamos la agenda por medio de un proceso de diálogo de dos años que involucró a casi 300 expertos de diversas disciplinas y localidades. Este proceso estuvo orientado por el conocimiento de las ciencias sociales que muestra cómo la investigación y la acción para la biodiversidad están sostenidas por las opciones de cómo están conceptualizados los problemas. Reconocimos al conocimiento, la acción y la ética como inseparables y sintetizamos un conjunto de principios que ayuda a navegar la labor de revisar la biodiversidad. La agenda articula cuatro áreas temáticas para la investigación en el futuro. Primero, los investigadores necesitan revisar las narrativas de la biodiversidad mediante el cuestionamiento de las conceptualizaciones que excluyen a la diversidad y consolidan la separación entre humanos, culturas, economías y sociedades y la naturaleza. Segundo, los investigadores deberían enfocarse en las relaciones entre el antropoceno, la biodiversidad y la cultura al considerar a la humanidad y la biodiversidad como interconectadas en contextos específicos. Tercero, los investigadores deberían enfocarse en la naturaleza y las economías al tener en mejor cuenta la interacción de las estructuras de los sistemas económico y financiero como conductores nucleares de la pérdida de la biodiversidad. Finalmente, los investigadores deberían permitir la investigación y acción transformadoras de la biodiversidad al reconfigurar las relaciones entre las comunidades humanas y no humanas dentro y a través de la ciencia, la política y la práctica. La revisión de la biodiversidad necesita de un enfoque renovado sobre el diálogo entre las comunidades de la biodiversidad y más allá, que reflexione críticamente sobre el pasado para canalizar a la investigación y acción hacia el fomento del futuro justo y diverso para la vida humana y no humana sobre la Tierra.

Recommendations for the nomenclature of enteroviruses and rhinoviruses.

Enteroviruses (EVs) and rhinoviruses (RVs) are significant pathogens of humans and are the subject of intensive clinical and epidemiological research and public health measures, notably in the eradication of poliovirus and in the investigation and control of emerging pathogenic EV types worldwide. EVs and RVs are highly diverse in their antigenic properties, tissue tropism, disease associations and evolutionary relationships, but the latter often conflict with previously developed biologically defined terms, such as "coxsackieviruses", "polioviruses" and "echoviruses", which were used before their genetic interrelationships were understood. This has created widespread formatting problems and inconsistencies in the nomenclature for EV and RV types and species in the literature and public databases. As members of the International Committee for Taxonomy of Viruses (ICTV) Picornaviridae Study Group, we describe the correct use of taxon names for these viruses and have produced a series of recommendations for the nomenclature of EV and RV types and their abbreviations. We believe their adoption will promote greater clarity and consistency in the terminology used in the scientific and medical literature. The recommendations will additionally provide a useful reference guide for journals, other publications and public databases seeking to use standardised terms for the growing multitude of enteroviruses and rhinoviruses described worldwide.

Correction to: Recommendations for the nomenclature of enteroviruses and rhinoviruses.

Unfortunately, one of the affiliations of author "A. E. Gorbalenya" was missed in original version. The affiliation is updated here.

ICTV Virus Taxonomy Profile: Picornaviridae.

The family Picornaviridae comprises small non-enveloped viruses with RNA genomes of 6.7 to 10.1 kb, and contains >30 genera and >75 species. Most of the known picornaviruses infect mammals and birds, but some have also been detected in reptiles, amphibians and fish. Many picornaviruses are important human and veterinary pathogens and may cause diseases of the central nervous system, heart, liver, skin, gastrointestinal tract or upper respiratory tract. Most picornaviruses are transmitted by the faecal-oral or respiratory routes. This is a summary of the International Committee on Taxonomy of Viruses (ICTV) Report on the taxonomy of the Picornaviridae, which is available at www.ictv.global/report/picornaviridae.

Heat stress affects carbohydrate metabolism during cold-induced sweetening of potato (Solanum tuberosum L.).

MAIN CONCLUSION: Tolerance to heat stress for retention of low-temperature sweetening-resistant phenotype in potato is conferred by insensitivity of acid invertase activity to cold induction. Heat stress exacerbated cold sweetening (buildup of reducing sugars) of the LTS (low-temperature sweetening)-susceptible potato (Solanum tuberosum L.) cultivars, Ranger Russet and Russet Burbank, and completely abolished the resistance to cold sweetening in the LTS-resistant cultivars/clones, Sage Russet, GemStar Russet, POR06V12-3 and A02138-2. Payette Russet and EGA09702-2, however, demonstrated considerable tolerance to heat stress for retention of their LTS-resistant phenotype. Heat-primed Payette Russet and EGA09702-2 tubers accumulated fourfold more sucrose when subsequently stored at 4 °C, while reducing sugar concentrations also increased marginally but remained low relative to the non-heat-tolerant LTS-resistant clones, resulting in light-colored fries. By contrast, sucrose concentrations in heat-primed tubers of the non-heat-tolerant clones remained unchanged during LTS, but reducing sugars increased fivefold, resulting in darkening of processed fries. Acid invertase activity increased in the LTS-susceptible and non-heat-tolerant LTS-resistant cultivars/clones during cold storage. However, Payette Russet tubers maintained very low invertase activity regardless of heat stress and cold storage treatments, as was the case for Innate® Russet Burbank (W8) tubers, where silenced invertase conferred robust tolerance to heat stress for retention of LTS-resistant phenotype. Importantly, heat-stressed tubers of Payette Russet, EGA09702-2 and Innate® Russet Burbank (W8) demonstrated similar low reducing sugar and high sucrose-accumulating phenotypes when stored at 4 °C. Tolerance to heat stress for retention of LTS-resistant phenotype in Payette Russet and likely its maternal parent, EGA09702-2, is, therefore, conferred by the ability to maintain low invertase activity during cold storage of heat-stressed tubers.

Zebra chip disease enhances respiration and oxidative stress of potato tubers (Solanum tuberosum L.).

MAIN CONCLUSION: The physiological phenotype of potato tubers afflicted by zebra chip disease is characterized by increased oxidative stress metabolism and upregulation of systems for its mitigation. Starch catabolism and extensive buildup of reducing sugars render potatoes infected with zebra chip (ZC) pathogen (Candidatus Liberibacter solanacearum) unsuitable for fresh market and processing into chips/fries. Here we show that the disease inflicts considerable oxidative stress, which likely constitutes a substantial sink for metabolic energy, resulting in increased respiration rate of afflicted tubers. In contrast to healthy tubers, tissue from diseased tubers had greater ability to reduce 2,3,5-triphenyl-tetrazolium chloride to formazan, indicating enhanced dehydrogenase activity, probable disease-induced changes in cellular redox potential, and increased respiratory activity. The respiration rate of diseased tubers (cv. Atlantic) was 2.4-fold higher than healthy tubers and this correlated with increased activities of glucose-6-phosphate and 6-phosphogluconate dehydrogenases, key enzymes responsible for synthesis of cytosolic reducing equivalents. Wound-induced NADPH oxidase activity was greater for ZC than healthy tubers, but the resulting superoxide was rapidly catabolized by higher superoxide dismutase activity in ZC tubers. Peroxidase, catalase, glutathione reductase and ascorbate free radical reductase activities were also higher in diseased tubers, as was malondialdehyde, a biomarker of peroxidative damage and oxidative stress. Upregulation of the glutathione-ascorbate pathway is a direct response to (and indicator of) oxidative stress, which consumes reducing equivalents (NADPH) to catabolize reactive oxygen species and maintain cellular redox homeostasis. ZC disease substantially altered the oxidative metabolism of tubers, resulting in a physiological phenotype defined by metabolic changes directed toward mitigating oxidative stress. Paradoxically, the increased respiration rate of ZC tubers, which fuels the metabolic pathways responsible for attenuating oxidative stress, likely also contributes to oxidative stress.

Characterization of Solanum tuberosum multicystatin and the significance of core domains.

Potato (Solanum tuberosum) multicystatin (PMC) is a unique cystatin composed of eight repeating units, each capable of inhibiting cysteine proteases. PMC is a composite of several cystatins linked by trypsin-sensitive (serine protease) domains and undergoes transitions between soluble and crystalline forms. However, the significance and the regulatory mechanism or mechanisms governing these transitions are not clearly established. Here, we report the 2.2-Šcrystal structure of the trypsin-resistant PMC core consisting of the fifth, sixth, and seventh domains. The observed interdomain interaction explains PMC's resistance to trypsin and pH-dependent solubility/aggregation. Under acidic pH, weakening of the interdomain interactions exposes individual domains, resulting in not only depolymerization of the crystalline form but also exposure of cystatin domains for inhibition of cysteine proteases. This in turn allows serine protease-mediated fragmentation of PMC, producing ∼ 10-kD domains with intact inhibitory capacity and faster diffusion, thus enhancing PMC's inhibitory ability toward cysteine proteases. The crystal structure, light-scattering experiments, isothermal titration calorimetry, and site-directed mutagenesis confirmed the critical role of pH and N-terminal residues in these dynamic transitions between monomer/polymer of PMC. Our data support a notion that the pH-dependent structural regulation of PMC has defense-related implications in tuber physiology via its ability to regulate protein catabolism.

VP1 sequencing protocol for foot and mouth disease virus molecular epidemiology.

Nucleotide sequences of field strains of foot and mouth disease virus (FMDV) contribute to our understanding of the distribution and evolution of viral lineages that circulate in different regions of the world. This paper outlines a practical reversetranscription polymerase chain reaction (RT-PCR) and sequencing strategy that can be used to generate RNA sequences encoding the VP1 (1D) region of FMDV. The protocol contains a panel of PCR and sequencing primers that can be selected to characterise genetically diverse isolates representing all seven FMDV serotypes. A list of sequences is also described, comprising prototype sequences for all proposed FMDV topotypes, in order to provide a framework for phylogenetic analysis. The technical details and prototype sequences provided in this paper can be employed by FMD Reference Laboratories and others in an approach to harmonise the molecular epidemiology of FMDV.

Les séquences de nucléotides des souches de terrain du virus de la fièvre aphteuse nous aident à comprendre la distribution et l'évolution des lignées virales présentes dans les différentes régions du monde. Les auteurs décrivent les grandes lignes d'un protocole pratique, basé sur l'amplification en chaîne par polymérase couplée à une transcription inverse (RT-PCR) et sur le séquençage, qui peut être utilisé pour générer des séquences d'ARN codant pour la région VP1 (1D) du virus de la fièvre aphteuse. Le protocole permet de procéder à une sélection parmi un panel de PCR et de marqueurs de séquençage dans le but de caractériser les gènes de divers isolats représentant les sept sérotypes du virus de la fièvre aphteuse. Les auteurs décrivent également une liste de séquences pouvant servir de cadre à l'analyse phylogénétique, dont des séquences prototypes pour tous les topotypes proposés du virus de la fièvre aphteuse. Les données techniques détaillées et les séquences prototypes fournies par les auteurs peuvent être utilisées par les Laboratoires de référence pour la fièvre aphteuse et d'autres institutions, en vue d'harmoniser l'épidémiologie moléculaire du virus de la fièvre aphteuse.

Las secuencias nucleotídicas de las cepas salvajes del virus de la fiebre aftosa nos ayudan a entender la distribución y evolución de los linajes víricos circulantes en distintas regiones del mundo. Los autores exponen sucintamente un práctico procedimiento de reacción en cadena de la polimerasa acoplada a transcripción inversa (RT-PCR) y de secuenciación que se puede utilizar para generar secuencias de ARN que codifican la región VP1 (1D) del virus de la fiebre aftosa. El protocolo ofrece la posibilidad de elegir entre todo un repertorio de cebadores de PCR y de secuenciación en el que están representados los siete serotipos víricos existentes con objeto de caracterizar genéticamente diversas cepas aisladas sobre el terreno. Los autores también presentan una lista de secuencias que comprende secuencias prototípicas de todos los topotipos propuestos del virus, a fin de proporcionar un marco de referencia para el análisis filogenético. Los laboratorios de referencia para la fiebre aftosa, así como otros establecimientos, pueden servirse de las detalladas técnicas y las secuencias prototípicas aquí presentadas para armonizar el estudio de la epidemiología molecular del virus de la fiebre aftosa.

Genomics and outbreaks: foot and mouth disease.

Foot and mouth disease virus (FMDV) is an animal pathogen of global economic significance. Identifying the sources of outbreaks plays an important role in disease control; however, this can be confounded by the ease with which FMDV can spread via movement of infected livestock and animal products, aerosols or fomites, e.g. contaminated persons and objects. As sequencing technologies have advanced, this review highlights the uses of viral genomic data in helping to understand the global distribution and transboundary movements of FMDV, and the role that these approaches have played in control and surveillance programmes. The recent application of next-generation sequencing platforms to address important epidemiological and evolutionary challenges is discussed with particular reference to the advent of 'omics' technologies.

Le virus de la fièvre aphteuse est un agent pathogène affectant les animaux d'élevage, avec des conséquences économiques considérables à l'échelle mondiale. La détection des sources des foyers est un aspect important de la lutte contre cette maladie ; l'efficacité de cette stratégie est toutefois compromise par la facilité avec laquelle le virus de la fièvre aphteuse se propage à la faveur des mouvements d'animaux ou de produits d'origine animale infectés, d'aérosols ou de personnes ou matières contaminées. Les auteurs décrivent, au fur et à mesure des avancées des technologies du séquençage, les données de la génomique virale qui ont permis de mieux comprendre la distribution mondiale et la propagation transfrontalière du virus de la fièvre aphteuse et le rôle que ces approches ont commencé à jouer dans les programmes de contrôle et de surveillance. Les auteurs examinent également les applications récentes des plates-formes de séquençage de nouvelle génération pour résoudre des problèmes épidémiologiques et évolutifs importants, en se référant particulièrement à l'avènement des technologies dites «­omiques ¼.

El virus de la fiebre aftosa es un patógeno animal que reviste importancia planetaria. A la hora de combatir la enfermedad es útil poder determinar el origen de los brotes, tarea que sin embargo puede verse frustrada por la facilidad con que el virus es capaz de diseminarse siguiendo los desplazamientos de animales o derivados animales infectados o por aerosoles o fómites (por ejemplo personas u objetos contaminados). Los autores hacen hincapié en la utilización de datos de genómica vírica para ayudar a aprehender la distribución mundial y los movimientos transfronterizos del virus de la fiebre aftosa, lo cual es posible gracias a los avances que han conocido las técnicas de secuenciación, así como en la función que pueden cumplir estos métodos dentro de los programas de control y vigilancia. También examinan la reciente aplicación de dispositivos de secuenciación de próxima generación para abordar importantes problemas epidemiológicos y evolutivos, refiriéndose especialmente al advenimiento de las técnicas «ómicas¼.

Zebra chip disease decreases tuber (Solanum tuberosum L.) protein content by attenuating protease inhibitor levels and increasing protease activities.

MAIN CONCLUSION: Zebra chip disease of potato decreases protease inhibitor levels resulting in enhanced serine-type protease activity, decreased protein content and altered protein profiles of fully mature tubers. Zebra-chip (ZC), caused by Candidatus Liberibacter solanacearum (CLso), is a relatively new disease of potato that negatively affects growth, yield, propagation potential, and fresh and process qualities of tubers. Diseased plants produce tubers with characteristic brown discoloration of vascular tissue accompanied by elevated levels of free amino acids and reducing sugars. Here we demonstrate that ZC disease induces selective protein catabolism in tubers through modulating protease inhibitor levels. Soluble protein content of tubers from CLso-infected plants was 33% lower than from non-infected plants and electrophoretic analyses revealed substantial reductions in major tuber proteins. Patatin (~40 kDa) and ser-, asp- (22 kDa) and cys-type (85 kDa) protease inhibitors were either absent or greatly reduced in ZC-afflicted tubers. In contrast to healthy (non-infected) tubers, the proteolytic activity in CLso infected tubers was high and the ability of extracts from infected tubers to inhibit trypsin (ser-type) and papain (cys-type) proteases greatly attenuated. Moreover, extracts from CLso-infected tubers rapidly catabolized proteins purified from healthy tubers (40 kDa patatin, 22 kDa protease inhibitors, 85 kDa potato multicystatin) when subjected to proteolysis individually. In contrast, crude extracts from non-infected tubers effectively inhibited the proteolytic activity from ZC-afflicted tubers. These results suggest that the altered protein profile of ZC afflicted tubers is largely due to loss of ser- and cys-type protease inhibitors. Further analysis revealed a novel PMSF-sensitive (ser) protease (ca. 80-120 kDa) in CLso infected tubers. PMSF abolished the proteolytic activities responsible for degrading patatin, the 22 kDa protease inhibitor(s) and potato multicystatin by CLso infected tubers. The disease-induced loss of patatin and protease inhibitors therefore appears to be modulated by ser-type protease(s). The selective catabolism of proteins in ZC-afflicted tubers undoubtedly affects downstream aspects of carbohydrate and amino acid metabolism, which is ultimately reflected by the accumulation of reducing sugars, free amino acids and reduced sprouting capacity.

Ratification vote on taxonomic proposals to the International Committee on Taxonomy of Viruses (2015).

Changes to virus taxonomy approved and ratified by the International Committee on Taxonomy of Viruses in February 2015 are listed.

Antigenic variation of foot-and-mouth disease virus serotype A.

The current measures to control foot-and-mouth disease (FMD) include vaccination, movement control and slaughter of infected or susceptible animals. One of the difficulties in controlling FMD by vaccination arises due to the substantial diversity found among the seven serotypes of FMD virus (FMDV) and the strains within these serotypes. Therefore, vaccination using a single vaccine strain may not fully cross-protect against all strains within that serotype, and therefore selection of appropriate vaccines requires serological comparison of the field virus and potential vaccine viruses using relationship coefficients (r1 values). Limitations of this approach are that antigenic relationships among field viruses are not addressed, as comparisons are only with potential vaccine virus. Furthermore, inherent variation among vaccine sera may impair reproducibility of one-way relationship scores. Here, we used antigenic cartography to quantify and visualize the antigenic relationships among FMD serotype A viruses, aiming to improve the understanding of FMDV antigenic evolution and the scope and reliability of vaccine matching. Our results suggest that predicting antigenic difference using genetic sequence alone or by geographical location is not currently reliable. We found co-circulating lineages in one region that were genetically similar but antigenically distinct. Nevertheless, by comparing antigenic distances measured from the antigenic maps with the full capsid (P1) sequence, we identified a specific amino acid substitution associated with an antigenic mismatch among field viruses and a commonly used prototype vaccine strain, A22/IRQ/24/64.

In-season heat stress compromises postharvest quality and low-temperature sweetening resistance in potato (Solanum tuberosum L.).

The effects of soil temperature during tuber development on physiological processes affecting retention of postharvest quality in low-temperature sweetening (LTS) resistant and susceptible potato cultivars were investigated. 'Premier Russet' (LTS resistant), AO02183-2 (LTS resistant) and 'Ranger Russet' (LTS susceptible) tubers were grown at 16 (ambient), 23 and 29 °C during bulking (111-164 DAP) and maturation (151-180 DAP). Bulking at 29 °C virtually eliminated yield despite vigorous vine growth. Tuber specific gravity decreased as soil temperature increased during bulking, but was not affected by temperature during maturation. Bulking at 23 °C and maturation at 29 °C induced higher reducing sugar levels in the proximal (basal) ends of tubers, resulting in non-uniform fry color at harvest, and abolished the LTS-resistant phenotype of 'Premier Russet' tubers. AO02183-2 tubers were more tolerant of heat for retention of LTS resistance. Higher bulking and maturation temperatures also accelerated LTS and loss of process quality of 'Ranger Russet' tubers, consistent with increased invertase and lower invertase inhibitor activities. During LTS, tuber respiration fell rapidly to a minimum as temperature decreased from 9 to 4 °C, followed by an increase to a maximum as tubers acclimated to 4 °C; respiration then declined over the remaining storage period. The magnitude of this cold-induced acclimation response correlated directly with the extent of buildup in sugars over the 24-day LTS period and thus reflected the effects of in-season heat stress on propensity of tubers to sweeten and lose process quality at 4 °C. While morphologically indistinguishable from control tubers, tubers grown at elevated temperature had different basal metabolic (respiration) rates at harvest and during cold acclimation, reduced dormancy during storage, greater increases in sucrose and reducing sugars and associated loss of process quality during LTS, and reduced ability to improve process quality through reconditioning. Breeding for retention of postharvest quality and LTS resistance should consider strategies for incorporating more robust tolerance to in-season heat stress.

Translucent tissue defect in potato (Solanum tuberosum L.) tubers is associated with oxidative stress accompanying an accelerated aging phenotype.

Translucent tissue defect (TTD) is an undesirable postharvest disorder of potato tubers characterized by the development of random pockets of semi-transparent tissue containing high concentrations of reducing sugars. Translucent areas turn dark during frying due to the Maillard reaction. The newly released cultivar, Premier Russet, is highly resistant to low temperature sweetening, but susceptible to TTD. Symptoms appeared as early as 170 days after harvest and worsened with time in storage (4-9 °C, 95 % RH). In addition to higher concentrations of glucose, fructose and sucrose, TTD resulted in lower dry matter, higher specific activities of starch phosphorylase and glc-6-phosphate dehydrogenase, higher protease activity, loss of protein, and increased concentrations of free amino acids (esp. asparagine and glutamine). The mechanism of TTD is unknown; however, the disorder has similarities with the irreversible senescent sweetening that occurs in tubers during long-term storage, where much of the decline in quality is a consequence of progressive increases in oxidative stress with advancing age. The respiration rate of non-TTD 'Premier Russet' tubers was inherently higher (ca. 40 %) than that of 'Russet Burbank' tubers (a non-TTD cultivar). Moreover, translucent tissue from 'Premier Russet' tubers had a 1.9-fold higher respiration rate than the average of non-translucent tissue and tissue from non-TTD tubers. Peroxidation of membrane lipids during TTD development resulted in increased levels of malondialdehyde and likely contributed to a measurable increase in membrane permeability. Superoxide dismutase and catalase activities and the ratio of oxidized to total glutathione were substantially higher in translucent tissue. TTD tubers also contained twofold less ascorbate than non-TTD tubers. TTD appears to be a consequence of oxidative stress associated with accelerated aging of 'Premier Russet' tubers.

Towards an integrated network of coral immune mechanisms.

Reef-building corals form bio-diverse marine ecosystems of high societal and economic value, but are in significant decline globally due, in part, to rapid climatic changes. As immunity is a predictor of coral disease and thermal stress susceptibility, a comprehensive understanding of this new field will likely provide a mechanistic explanation for ecological-scale trends in reef declines. Recently, several strides within coral immunology document defence mechanisms that are consistent with those of both invertebrates and vertebrates, and which span the recognition, signalling and effector response phases of innate immunity. However, many of these studies remain discrete and unincorporated into the wider fields of invertebrate immunology or coral biology. To encourage the rapid development of coral immunology, we comprehensively synthesize the current understanding of the field in the context of general invertebrate immunology, and highlight fundamental gaps in our knowledge. We propose a framework for future research that we hope will stimulate directional studies in this emerging field and lead to the elucidation of an integrated network of coral immune mechanisms. Once established, we are optimistic that coral immunology can be effectively applied to pertinent ecological questions, improve current prediction tools and aid conservation efforts.

Combining livestock trade patterns with phylogenetics to help understand the spread of foot and mouth disease in sub-Saharan Africa, the Middle East and Southeast Asia.

International trade in animals and their products is recognised as a primary determinant of the global epidemiology of transboundary diseases such as foot and mouth disease (FMD). As well as causing serious production losses, FMD is highly contagious, being transmitted through multiple routes and hosts, which makes it one of the most important diseases affecting trade in livestock. Its occurrence has dramatic consequences for the agricultural economy of a normally disease-free country, as well as for the livelihoods and income generation of developing countries where the disease continues to be endemic. In the dynamic of FMD virus (FMDV) dispersal across the globe, phylogenetic inference from molecular sequences of isolated viruses makes a significant contribution to investigating the evolutionary and spatial pathways underlying the source of FMD epidemics. Matching data on livestock movement with molecular epidemiology can enhance our fundamental understanding when reconstructing the spread of the virus between geographical regions, which is essential for the development of FMD control strategies worldwide. This paper reviews the global situation of FMD in the last ten years, combining phylogenetic insights with information on livestock production systems and international trade to analyse the epidemiological dynamics of FMD and the sources of FMDV introductions at a regional level in sub-Saharan Africa, the Middle East and Southeast Asia.

Age-induced loss of wound-healing ability in potato tubers is partly regulated by ABA.

Wounding of potato (Solanum tuberosum L.) tubers induces the development of a suberized closing layer and wound periderm that resists desiccation and microbial invasion. Wound-healing ability declines with tuber age (storage period). The mechanism of loss in healing capacity with age is not known; however, upregulation of superoxide production, increased ABA biosynthesis and phenylalanine ammonia lyase (PAL) activity in response to wounding are processes critical to the development of a suberized closing layer and wound periderm. Therefore, the role of ABA in modulating the age-induced loss of wound-healing ability of tubers was examined. Non-wounded older tubers had 86% less ABA (dry matter basis) than younger tubers. PAL transcript increased in younger tubers within 24 h of wounding, but transcription was delayed by 5 days in older tubers. Wound-induced PAL activity increased more rapidly in younger than older tubers. ABA treatment increased PAL expression and activity in tissue from both ages of tubers and restored the 24 h transcription time line in older tubers. Moreover, ABA treatment of wounded older tubers enhanced their resistance to water vapor loss following a 6-day wound-healing period. Wound-induced accumulation of suberin poly(phenolic(s)) (SPP) and suberin poly(aliphatic(s)) (SPA) was measurably slower in older versus younger tubers. ABA treatment hastened SPP accumulation in older tubers to match that in younger tubers, but only enhanced SPA accumulations over the initial 4 days of healing. Age-induced loss of wound-healing ability is thus partly due to reduced ability to accumulate ABA and modulate the production of SPP through PAL in response to wounding and to dysfunction in the downstream signaling events that couple SPA biosynthesis and/or deposition to ABA. ABA treatment partly restored the healing ability of older tubers by enhancing the accumulation of SPP without restoring wound-induced superoxide forming ability to the level of younger tubers. The coupling of phenolic monomers into the poly(phenolic) domain of suberin was therefore not limited by the diminished wound-induced superoxide production of older tubers.

Developmentally linked changes in proteases and protease inhibitors suggest a role for potato multicystatin in regulating protein content of potato tubers.

The soluble protein fraction of fully developed potato (Solanum tuberosum L.) tubers is dominated by patatin, a 40 kD storage glycoprotein, and protease inhibitors. Potato multicystatin (PMC) is a multidomain Cys-type protease inhibitor. PMC effectively inhibits degradation of patatin by tuber proteases in vitro. Herein we show that changes in PMC, patatin concentration, activities of various proteases, and their gene expression are temporally linked during tuber development, providing evidence that PMC has a role in regulating tuber protein content in vivo. PMC was barely detectable in non-tuberized stolons. PMC transcript levels increased progressively during tuberization, concomitant with a 40-fold increase in PMC concentration (protein basis) as tubers developed to 10 g fresh wt. Further increases in PMC were comparatively modest (3.7-fold) as tubers developed to full maturity (250 g). Protease activity declined precipitously as PMC levels increased during tuberization. Proteolytic activity was highest in non-tuberized stolons and fell substantially through the 10-g fresh wt stage. Cys-type proteases dominated the pre-tuberization and earliest stages of tuber development. Increases in patatin transcript levels during tuberization were accompanied by a notable lag in patatin accumulation. Patatin did not begin to accumulate substantially on a protein basis until tubers had reached the 10-g stage, wherein protease activity had been inhibited by approximately 60%. These results indicate that a threshold level of PMC (ca. 3 microg tuber(-1), 144 ng mg(-1) protein) is needed to favor patatin accumulation. Collectively, these results are consistent with a role for PMC in facilitating the accumulation of proteins in developing tubers by inhibiting Cys-type proteases.

Identification of chicken enterovirus-like viruses, duck hepatitis virus type 2 and duck hepatitis virus type 3 as astroviruses.

Earlier work identified and biologically characterized antigenically distinct enterovirus-like viruses (ELVs) of chickens. Three of these ELVs can now be identified as astroviruses. Characterization involved the use of a hitherto undescribed, degenerate primer-based reverse transcription-polymerase chain reaction (RT-PCR) to amplify astrovirus open reading frame (ORF) 1b-specific cDNA fragments followed by nucleotide sequence determination and analysis of the amplified fragments. ELV-1 was confirmed as an isolate of the astrovirus avian nephritis virus (ANV). ELV-4 (isolate 612) and ELV-3 (isolates FP3 and 11672) were antigenically and genetically related to the second characterized astrovirus of chickens, namely chicken astrovirus (CAstV). Using indirect immunofluorescence, the FP3 and 11672 ELV-3 isolates were very closely related to one another, and less closely related to ELV-4 and the previously described CAstV (P22 18.8.00 reference isolate). Comparative analyses based on the ORF 1b amplicon sequences showed that the FP3 and 11672 ELV-3 isolates shared high nucleotide (95%) and amino acid (98%) identities with one another, and lower nucleotide (76% to 79%) and amino acid (84% to 85%) identity levels with ELV-4 and the reference CAstV P22 18.8.00 isolates. The combined degenerate primer RT-PCR and sequencing methods also provided a nucleotide sequence specific to duck hepatitis virus type 2 (DHV-2) (renamed duck astrovirus) and duck hepatitis virus type 3 (DHV-3), which, for the first time, can also be identified as an astrovirus. Phylogenetic analyses based on the amplified ORF 1b sequences showed that ANV was the most distantly related avian astrovirus, with DHV-3 being more closely related to turkey astrovirus type 2 than DHV-2.