Modulation of gene expression in ex vitro grapevine (Vitis vinifera L.) by hormonal, oxidant and anti-oxidant stimuli

When in vitro plantlets developed under low light conditions are exposed to high light upon transfer to ex vitro, it is common to observe symptoms of oxidative stress. In order to unravel more of what takes place in this phase of transition, paramount for plant survival, the present study focused on the expression of genes coding for proteins related with the metabolic pathways most affected upon transfer to ex vitro and monitored their expression in response to hormones and chemicals inducing alternative sinks for photosynthetic electron transport (PET) and reactive oxygen species (ROS) production. The expression of eight genes was significantly downregulated after all the treatments: catalase, beta-glucosidase, cytochrome P450, vegetative storage protein 2, wak1, a calcium binding protein, a meprin and TRAF homology domain-containing protein and a serine/threonine kinase. It was possible to verify that abscisic acid (ABA) was able to revert light induced gene expression and that the PET inhibitors DCMU and DPI had the same effect as ABA. ABA and jasmonic acid showed parallel effects, as both induced the expression of the same set of genes. Finally, exogenous cytokinin, instead of enhancing the plant´s response to high light led to the downregulation of light-responsive genes

Dynamical complexity of discrete time regulatory networks

Genetic regulatory networks are usually modeled by systems of coupled differential equations and by finite state models, better known as logical networks, are also used. In this paper we consider a class of models of regulatory networks which present both discrete and continuous aspects. Our models consist of a network of units, whose states are quantified by a continuous real variable. The state of each unit in the network evolves according to a contractive transformation chosen from a finite collection of possible transformations, according to a rule which depends on the state of the neighboring units. As a first approximation to the complete description of the dynamics of this networks we focus on a global characteristic, the dynamical complexity, related to the proliferation of distinguishable temporal behaviors. In this work we give explicit conditions under which explicit relations between the topological structure of the regulatory network, and the growth rate of the dynamical complexity can be established. We illustrate our results by means of some biologically motivated examples.Comment: 28 pages, 4 figure

Stratification of the orbit space in gauge theories. The role of nongeneric strata

Gauge theory is a theory with constraints and, for that reason, the space of physical states is not a manifold but a stratified space (orbifold) with singularities. The classification of strata for smooth (and generalized) connections is reviewed as well as the formulation of the physical space as the zero set of a momentum map. Several important features of nongeneric strata are discussed and new results are presented suggesting an important role for these strata as concentrators of the measure in ground state functionals and as a source of multiple structures in low-lying excitations.Comment: 22 pages Latex, 1 figur

Validação de marcadores microssatélites em Urochloa decumbens e avaliação da transferibilidade para outras espécies deste gênero.

Comissão organizadora: Grácia Maria Soares Rosinha, Alexandra Rocha de Oliveir, Rodrigo Carvalho Alva

Produção de sementes de alfafa (Medicago sativa) na região Sudeste do Brasil.

Em um experimento conduzido na Embrapa Pecuária Sudeste, São Carlos, SP, avaliou-se o potencial de produção de sementes da alfafa LE N 4, na região Sudeste do Brasil. O rendimento e a qualidade das sementes foram medidos em 20 parcelas de 3m2, distribuídas ao acaso em uma área irrigada de 2.000m2. O rendimento médio foi de 421 kg/ha de sementes de alfafa. Concluiu-se que a região tem potencial para produzir sementes dessa forrageira

Selection of the fall armyworm Spodoptera frugiperda (Smith) (Lepidoptera: Noctuidae) for survival on Cry 1A (b) Bt toxin.

Plantas transgênicas que expressam toxinas da bactéria Bacillus thuringiensis (Bt) representam um importante avanço para o controle de lepidópteros-pragas de milho. Híbridos de milho Bt expressando a toxina Cry1A(b) têm mostrado significativo nível de resistência à lagarta-do-cartucho (LCM), Spodoptera frugiperda (Smith) (Lepidoptera: Noctuidae), embora larvas dessa espécie tenham sido observadas em campo e em laboratório sobrevivendo nesses híbridos. Resistência de S. frugiperda também tem sido registrada para diferentes inseticidas. Em bioensaios, seleção de insetos sobreviventes mostrou um aumento do nível de tolerância à toxina do Bt Cry1A(b) em populações da lagarta-do-cartucho, após quatro gerações, indicando que essa tolerância é herdada. Palavras-chave: Insecta, resistência, plantas transgênicas

On the regular-geometric-figure solution to the N-body problem

The regular-geometric-figure solution to the $N$-body problem is presented in a very simple way. The Newtonian formalism is used without resorting to a more involved rotating coordinate system. Those configurations occur for other kinds of interactions beyond the gravitational ones for some special values of the parameters of the forces. For the harmonic oscillator, in particular, it is shown that the $N$-body problem is reduced to $N$ one-body problems.Comment: To appear in Eur. J. Phys. (5 pages