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Publicações

Publicações por Nuno Fonseca

2010

Evolutionary patterns at the RNase based gametophytic self-incompatibility system in two divergent Rosaceae groups (Maloideae and Prunus)

Autores
Vieira, J; Ferreira, PG; Aguiar, B; Fonseca, NA; Vieira, CP;

Publicação
BMC EVOLUTIONARY BIOLOGY

Abstract
Background: Within Rosaceae, the RNase based gametophytic self-incompatibility (GSI) system has been studied at the molecular level in Maloideae and Prunus species that have been diverging for, at least, 32 million years. In order to understand RNase based GSI evolution within this family, comparative studies must be performed, using similar methodologies. Result: It is here shown that many features are shared between the two species groups such as levels of recombination at the S-RNase ( the S-pistil component) gene, and the rate at which new specificities arise. Nevertheless, important differences are found regarding the number of ancestral lineages and the degree of specificity sharing between closely related species. In Maloideae, about 17% of the amino acid positions at the S-RNase protein are found to be positively selected, and they occupy about 30% of the exposed protein surface. Positively selected amino acid sites are shown to be located on either side of the active site cleft, an observation that is compatible with current models of specificity determination. At positively selected amino acid sites, non-conservative changes are almost as frequent as conservative changes. There is no evidence that at these sites the most drastic amino acid changes may be more strongly selected. Conclusions: Many similarities are found between the GSI system of Prunus and Maloideae that are compatible with the single origin hypothesis for RNase based GSI. The presence of common features such as the location of positively selected amino acid sites and lysine residues that may be important for ubiquitylation, raise a number of issues that, in principle, can be experimentally addressed in Maloideae. Nevertheless, there are also many important differences between the two Rosaceae GSI systems. How such features changed during evolution remains a puzzling issue.

2005

On predicting protein secondary structure from their aminoacid sequences using Inductive Logic Programming

Autores
Magalhaes, A; Fonseca, NA;

Publicação
2005 PORTUGUESE CONFERENCE ON ARTIFICIAL INTELLIGENCE, PROCEEDINGS

Abstract
We address the problem of predicting the stability of secondary structure motifs of proteins given their linear sequence of residues. Our study is restricted to the prediction of helix structures. We have applied an Inductive Logic Programming (ILP) system to automatically synthesise the predictive rules. ILP systems are well known for being able to induce comprehensible models for data. Furthermore, the models components are definitions provided by a domain expert which makes the model more likely to be helpful in the understanding of the underlying process that produced the data. Our methodology has two stages. First, the system induces a model (set of rules) using just structural information and groupings of the residues to avoid biases by the domain expert. In the second stage, the residues properties are used to make the induced rules Chemically/Biologically appealing. We claim that this methodology is also valuable for general Structure-Activity Relationship (SAR) problems.

2011

Assemblathon 1: A competitive assessment of de novo short read assembly methods

Autores
Earl, D; Bradnam, K; St John, J; Darling, A; Lin, DW; Fass, J; Hung, OKY; Buffalo, V; Zerbino, DR; Diekhans, M; Nguyen, N; Ariyaratne, PN; Sung, WK; Ning, ZM; Haimel, M; Simpson, JT; Fonseca, NA; Birol, I; Docking, TR; Ho, IY; Rokhsar, DS; Chikhi, R; Lavenier, D; Chapuis, G; Naquin, D; Maillet, N; Schatz, MC; Kelley, DR; Phillippy, AM; Koren, S; Yang, SP; Wu, W; Chou, WC; Srivastava, A; Shaw, TI; Ruby, JG; Skewes Cox, P; Betegon, M; Dimon, MT; Solovyev, V; Seledtsov, I; Kosarev, P; Vorobyev, D; Ramirez Gonzalez, R; Leggett, R; MacLean, D; Xia, FF; Luo, RB; Li, ZY; Xie, YL; Liu, BH; Gnerre, S; MacCallum, I; Przybylski, D; Ribeiro, FJ; Yin, SY; Sharpe, T; Hall, G; Kersey, PJ; Durbin, R; Jackman, SD; Chapman, JA; Huang, XQ; DeRisi, JL; Caccamo, M; Li, YR; Jaffe, DB; Green, RE; Haussler, D; Korf, I; Paten, B;

Publicação
GENOME RESEARCH

Abstract
Low-cost short read sequencing technology has revolutionized genomics, though it is only just becoming practical for the high-quality de novo assembly of a novel large genome. We describe the Assemblathon 1 competition, which aimed to comprehensively assess the state of the art in de novo assembly methods when applied to current sequencing technologies. In a collaborative effort, teams were asked to assemble a simulated Illumina HiSeq data set of an unknown, simulated diploid genome. A total of 41 assemblies from 17 different groups were received. Novel haplotype aware assessments of coverage, contiguity, structure, base calling, and copy number were made. We establish that within this benchmark: ( 1) It is possible to assemble the genome to a high level of coverage and accuracy, and that ( 2) large differences exist between the assemblies, suggesting room for further improvements in current methods. The simulated benchmark, including the correct answer, the assemblies, and the code that was used to evaluate the assemblies is now public and freely available from http://www.assemblathon.org/.

2011

Amino acid pair- and triplet-wise groupings in the interior of alpha-helical segments in proteins

Autores
de Sousa, MM; Munteanu, CR; Pazos, A; Fonseca, NA; Camacho, R; Magalhaes, AL;

Publicação
JOURNAL OF THEORETICAL BIOLOGY

Abstract
A statistical approach has been applied to analyse primary structure patterns at inner positions of alpha-helices in proteins. A systematic survey was carried out in a recent sample of non-redundant proteins selected from the Protein Data Bank, which were used to analyse alpha-helix structures for amino acid pairing patterns. Only residues more than three positions apart from both termini of the alpha-helix were considered as inner. Amino acid pairings i, i+k(k = 1, 2, 3,4, 5), were analysed and the corresponding 20 x 20 matrices of relative global propensities were constructed. An analysis of (i, i+4, i+8) and (i, i+3, i+4) triplet patterns was also performed. These analysis yielded information on a series of amino acid patterns (pairings and triplets) showing either high or low preference for alpha-helical motifs and suggested a novel approach to protein alphabet reduction. In addition, it has been shown that the individual amino acid propensities are not enough to define the statistical distribution of these patterns. Global pair propensities also depend on the type of pattern, its composition and orientation in the protein sequence. The data presented should prove useful to obtain and refine useful predictive rules which can further the development and fine-tuning of protein structure prediction algorithms and tools.

2011

PopAffiliator: online calculator for individual affiliation to a major population group based on 17 autosomal short tandem repeat genotype profile

Autores
Pereira, L; Alshamali, F; Andreassen, R; Ballard, R; Chantratita, W; Cho, NS; Coudray, C; Dugoujon, JM; Espinoza, M; Gonzalez Andrade, F; Hadi, S; Immel, UD; Marian, C; Gonzalez Martin, A; Mertens, G; Parson, W; Perone, C; Prieto, L; Takeshita, H; Rangel Villalobos, HR; Zeng, ZS; Zhivotovsky, L; Camacho, R; Fonseca, NA;

Publicação
INTERNATIONAL JOURNAL OF LEGAL MEDICINE

Abstract
Because of their sensitivity and high level of discrimination, short tandem repeat (STR) maker systems are currently the method of choice in routine forensic casework and data banking, usually in multiplexes up to 15-17 loci. Constraints related to sample amount and quality, frequently encountered in forensic casework, will not allow to change this picture in the near future, notwithstanding the technological developments. In this study, we present a free online calculator named PopAffiliator (http://cracs.fc.up.pt/popaffiliator) for individual population affiliation in the three main population groups, Eurasian, East Asian and sub-Saharan African, based on genotype profiles for the common set of STRs used in forensics. This calculator performs affiliation based on a model constructed using machine learning techniques. The model was constructed using a data set of approximately fifteen thousand individuals collected for this work. The accuracy of individual population affiliation is approximately 86%, showing that the common set of STRs routinely used in forensics provide a considerable amount of information for population assignment, in addition to being excellent for individual identification.

2009

RNase-Based Gametophytic Self-Incompatibility Evolution: Questioning the Hypothesis of Multiple Independent Recruitments of the S-Pollen Gene

Autores
Vieira, J; Fonseca, NA; Vieira, CP;

Publicação
JOURNAL OF MOLECULAR EVOLUTION

Abstract
Multiple independent recruitments of the S-pollen component (always an F-box gene) during RNase-based gametophytic self-incompatibility evolution have recently been suggested. Therefore, different mechanisms could be used to achieve the rejection of incompatible pollen in different plant families. This hypothesis is, however, mainly based on the interpretation of phylogenetic analyses, using a small number of divergent nucleotide sequences. In this work we show, based on a large collection of F-box S-like sequences, that the inferred relationship of F-box S-pollen and F-box S-like sequences is dependent on the sequence alignment software and phylogenetic method used. Thus, at present, it is not possible to address the phylogenetic relationship of F-box S-pollen and S-like sequences from different plant families. In Petunia and Malus/ Pyrus the putative S-pollen gene(s) show(s) variability patterns different than expected for an S-pollen gene, raising the question of false identification. Here we show that in Petunia, the unexpected features of the putative S-pollen gene are not incompatible with this gene's being the S-pollen gene. On the other hand, it is very unlikely that the Pyrus SFBB-gamma gene is involved in specificity determination.

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