BackgroundSouth American leaf blight (SALB) of rubber has been the main constraint to production in its neotropical centre of origin since commercial plantations were first established. The fungal causal agent was identified and described more than a century ago but its precise placement within the Ascomycota still remains uncertain. Indeed, such is the ambiguity surrounding the pathogen that each of the spore morphs would, according to their present classification, be placed in different ascomycete families: the Microcyclus sexual morph in the Planistromellaceae and the two purported asexual morphs - Fusicladium and Aposphaeria – in the Venturiaceae and Lophiostomataceae, respectively. Given the historical importance of the fungus and the ever-menacing threat that it poses to rubber production in the Palaeotropics – and, thus to the rubber industry and to the global economy – its phylogeny, as well as its biology, should be resolved as a matter of urgency.Methods and ResultsHere, six genomic regions (LSU rRNA, mtSSU, MCM7, EF-1α, Act and ITS) were used for reconstructing the molecular phylogeny of the SALB fungus based on material collected throughout Brazil. The analyses support the classification of the fungus in the family Mycosphaerellaceae s. str. (Capnodiales, Dothideomycetes) and place it firmly within the clade Pseudocercospora s. str., now accepted as one of the distinct genera within Mycosphaerellaceae. The new combination Pseudocercospora ulei is proposed and the life cycle of the fungus is confirmed, based on both experimental and phylogenetic evidence, with the Aposphaeria morph shown to have a spermatial rather than an infective-dispersal function.ConclusionsBecause the phylogeny of the SALB fungus has now been clarified, new insights of its epidemiology and genomics can be gained following comparison with closely-related, better-researched crop pathogens.
Soybean root and stem rot caused by the oomycete Phytophthora sojae is a destructive disease worldwide that can affect plants at any growth stage. The use of resistant cultivars is the most effective method of controlling the disease. Therefore, monitoring changes in the population of P. sojae regarding the dynamics of avirulence genes capable of overcoming resistance genes (Rps) is important to reduce yield losses and to enhance the effectiveness of the Rps genes. Forty isolates of P. sojae sampled from a region of high incidence of soybean root and stem rot in Brazil were characterized using 14 soybean differentials and 28 pathotypes were identified. Compared to a study conducted a decade ago there was a major shift in pathotype diversity and complexity towards both higher numbers of different pathotypes and of avirulence genes in a given individual in the current population of P. sojae. Breeding programs aiming at developing soybean cultivars with resistance to root and stem rot should consider the high variability in the population of P. sojae and seek for strategic deployment of genes and germplasm.
The Witches' Broom Disease, caused by the hemibiotrophic basidiomycete fungus Moniliophthora perniciosa, drastically reduced the production of cocoa in Brazil. Phytosanitation, chemical control, genetically resistant strains, and biological control still leave flaws in the disease eradication process. Effort has been expended in the elucidation of molecular targets, in particular, the structural components of the fungal cell wall, such as the beta(1,3)-D-glucan synthase. This enzyme is essential for the cellular construction of the wall, as it catalyses the formation of beta(1,3)-D-glucans. Protein structure homology modeling approaches are able to determine the structure of proteins without performing experimental steps, considering the barriers related to experimental methods for the structural determination of molecular targets. The presence of the conserved catalytic residues in members of the same glycosyltransferase family and overall structural analysis suggests that they catalyze glycosyl transfer reactions by similar mechanisms. Therefore, the objective of this study was to determine the three-dimensional model of the enzyme beta(1,3)-D-glucan synthase of M. perniciosa by homology modeling. Both procedures were performed to build the models: a comparative modeling by satisfaction of spatial restraints in MODELLER and a modeling by assembly of rigid bodies in the SWISS-MODEL software. The models were elected based on analysis of the stereochemistry quality and a quantitative assessment of similarity from the obtained models and to templates. A reasonable structural model was obtained of the beta(1,3)-D-glucan synthase enzyme (BegS1). The BegS1 model showed two distinct a/b domains, features of the inverting glycosyltransferase family, and the topology of the folded structure showed 7 beta-strands and 13 alpha-helices. The BegS1 model showed the presence of a catalytic cavity formed by the conserved aspartic acid residues (Asp326, 345, 353, and 354 DDxD motif ) implicated in substrate binding and/ or catalysis. In the BegS1 model, this cavity is near a loop region, as was observed in the GT-2 family structure. It is encouraging to find that the model for BegS1 agrees well with structures from the GT-2 enzyme family.
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Foram analisados os conteúdos gastro-intestinais de 60 exemplares de Caranx latus, 41 de Trachinotus carolinus, 4 de T. falcatus e 9 de T. goodei (Actinopterygii, Carangidae) coletados na Praia de Ponta da Ilha (sul da Ilha de Itaparica, cerca de 13o07’S - 38o45’W, Bahia). Em ocorrência, para C. latus, matéria orgânica digerida (MOD, 100,0%) e matéria inorgânica (30,0%); em T. carolinus, restos de Crustacea (46,3%) e MOD (43,9%); para T. falcatus, Copepoda, Isopoda, Amphipoda e restos de vegetais superiores (50,0% cada) e em T. goodei, restos de Crustacea, Bivalva e restos de vegetais superiores (44,4% cada).
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