Universidade Federal de Viçosa

About: Universidade Federal de Viçosa is a education organization based out in Viçosa, Brazil. It is known for research contribution in the topics: Population & Biology. The organization has 16012 authors who have published 26711 publications receiving 353416 citations.

The New Scope of Virus Taxonomy: Partitioning the Virosphere Into 15 Hierarchical Ranks

Abstract: Virus taxonomy emerged as a discipline in the middle of the twentieth century. Traditionally, classification by virus taxonomists has been focussed on the grouping of relatively closely related viruses. However, during the past few years, the International Committee on Taxonomy of Viruses (ICTV) has recognized that the taxonomy it develops can be usefully extended to include the basal evolutionary relationships among distantly related viruses. Consequently, the ICTV has changed its Code to allow a 15-rank classification hierarchy that closely aligns with the Linnaean taxonomic system and may accommodate the entire spectrum of genetic divergence in the virosphere. The current taxonomies of three human pathogens, Ebola virus, severe acute respiratory syndrome coronavirus and herpes simplex virus 1 are used to illustrate the impact of the expanded rank structure. This new rank hierarchy of virus taxonomy will stimulate further research on virus origins and evolution, and vice versa, and could promote crosstalk with the taxonomies of cellular organisms.

Thioredoxin, a master regulator of the tricarboxylic acid cycle in plant mitochondria

Abstract: Plant mitochondria have a fully operational tricarboxylic acid (TCA) cycle that plays a central role in generating ATP and providing carbon skeletons for a range of biosynthetic processes in both heterotrophic and photosynthetic tissues. The cycle enzyme-encoding genes have been well characterized in terms of transcriptional and effector-mediated regulation and have also been subjected to reverse genetic analysis. However, despite this wealth of attention, a central question remains unanswered: "What regulates flux through this pathway in vivo?" Previous proteomic experiments with Arabidopsis discussed below have revealed that a number of mitochondrial enzymes, including members of the TCA cycle and affiliated pathways, harbor thioredoxin (TRX)-binding sites and are potentially redox-regulated. We have followed up on this possibility and found TRX to be a redox-sensitive mediator of TCA cycle flux. In this investigation, we first characterized, at the enzyme and metabolite levels, mutants of the mitochondrial TRX pathway in Arabidopsis: the NADP-TRX reductase a and b double mutant (ntra ntrb) and the mitochondrially located thioredoxin o1 (trxo1) mutant. These studies were followed by a comparative evaluation of the redistribution of isotopes when (13)C-glucose, (13)C-malate, or (13)C-pyruvate was provided as a substrate to leaves of mutant or WT plants. In a complementary approach, we evaluated the in vitro activities of a range of TCA cycle and associated enzymes under varying redox states. The combined dataset suggests that TRX may deactivate both mitochondrial succinate dehydrogenase and fumarase and activate the cytosolic ATP-citrate lyase in vivo, acting as a direct regulator of carbon flow through the TCA cycle and providing a mechanism for the coordination of cellular function.

The tomato borer Tuta absoluta in South America: pest status, management and insecticide resistance

Abstract: The tomato borer Tuta absoluta (Lepidoptera: Gelechiidae) has been a recognized pest in South America since the 1960s, quickly spreading to the major tomato-producing countries in the region. A series of studies regarding this pest's biology, ecology and management were conducted to contain tomato losses within acceptable levels. Although cultural control methods were attempted against T. absoluta, as were the development of resistant tomato varieties and the use of pheromones and natural enemies, insecticides are still the main control method used. The sex pheromone of T. absoluta was identified, confirmed and synthesized in the late 1990s and it is currently used for detection and monitoring of this species, but improved sampling plans are still necessary for its use in decision-making regarding insecticide use. Insecticide use has shifted from earlier reliance on organophosphates, pyrethroids, cartap and abamectin to insect growth regulators and, more recently, to novel insecticides. Unfortunately, the overreliance on insecticide use led to problems with insecticide resistance in the region, which is a current matter of concern not only in South America, but also elsewhere since introduced strains may carry insecticide-resistance genes at high frequency even without local selection in the site of introduction. La mineuse de la tomate Tuta absoluta en Amerique du Sud: impact, controle et resistance aux insecticides La mineuse de la tomate Tuta absoluta (Lepidoptera: Gelechiidae) est consideree comme un ravageur en Amerique du Sud depuis les annees 1960, ou elle s'est rapidement disseminee dans les principaux pays produisant des tomates. Une serie d'etudes concernant la biologie de ce ravageur, son ecologie et sa gestion a ete menee pour limiter les pertes de tomate a des niveaux acceptables. Malgre des essais de developpement de lutte alternative (methodes culturales, varietes de tomates resistantes, utilisation de pheromones ou d'ennemis naturels), l'utilisation d'insecticides reste la principale methode de lutte utilisee contre T. absoluta. La pheromone sexuelle de T. absoluta a ete identifiee, confirmee et synthetisee a la fin des annees 1990 et est actuellement utilisee pour la detection et le suivi de cet insecte. Cependant, il faudrait encore ameliorer les plans d'echantillonnage pour pouvoir l'utiliser dans la prise de decision concernant l'utilisation d'insecticides. L'utilisation d'insecticides domine; elle ne repose plus comme avant sur les organophosphores, les pyrethrinoides, le cartap et l'abamectine, mais sur des regulateurs de croissance des insectes et plus recemment sur de nouveaux insecticides. Malheureusement, la dependance excessive a l'utilisation d'insecticides a conduit a des problemes de resistance aux insecticides dans la region, qui est une preoccupant non seulement en Amerique du Sud, mais aussi ailleurs puisque des souches introduites peuvent porter des genes de resistance aux insecticides a haute frequence, meme sans selection locale dans le site d'introduction.

El Niño–Southern oscillation and the climate, ecosystems and rivers of Amazonia

Abstract: [1] The El Nino–Southern Oscillation (ENSO) phenomenon is one of the dominant drivers of environmental variability in the tropics. In this study, we examine the connections between ENSO and the climate, ecosystem carbon balance, surface water balance, and river hydrology of the Amazon and Tocantins river basins in South America. First we examine the climatic variability associated with ENSO. We analyze long-term historical climate records to document the “average” climatic signature of the El Nino and La Nina phases of the ENSO cycle. Generally speaking, the “average El Nino” is drier and warmer than normal in Amazonia, while the “average La Nina” is wetter and cooler. While temperature changes are mostly uniform through the whole year and are spatially homogeneous, precipitation changes are stronger during the wet season (January-February-March) and are concentrated in the northern and southeastern portions of the basin. Next we use a land surface/ecosystem model (IBIS), coupled to a hydrological routing algorithm (HYDRA), to examine how ENSO affects land surface water and carbon fluxes, as well as changes in river discharge and flooding. The model results suggest several responses to ENSO: (1) During the average El Nino, there is an anomalous source of CO2 from terrestrial ecosystems, mainly due to a decreased net primary production (NPP) in the north of the basin. There is also a decrease in river discharge along many of the rivers in the basin, which causes a decrease in flooded area along the main stem of the Amazon. (2) During the average La Nina, there is an anomalous sink of CO2 into terrestrial ecosystems, largely due to an increase in NPP in the northern portion of the basin. In addition, there is a large increase in river discharge in the Amazon basin, especially from the northern and western tributaries. There is a corresponding increase in flooded area, largely in the northern rivers. These results illustrate that changes in water and carbon balance associated with ENSO have complex, spatially heterogeneous features across the basin. This underscores the need for comprehensive analyses, using long-term observational data and model simulations, of regional environmental systems and their response to climatic variability.