INVESTIGADORES
PRATTA Guillermo Raul
congresos y reuniones científicas
Título:
Heterosis for tomato fruit polypeptide profiles assessed by permutational MANOVA
Autor/es:
MACAT, PAULA; QUAGLINO, M.; PRATTA, G.R.
Lugar:
Bahía Blanca
Reunión:
Conferencia; VI Argentinian Conference on Bioinformatics and Computational Biology; 2015
Institución organizadora:
Asociación Argentina de Bioinformática y Biología Computacional
Resumen:
Tomato (Solanum lycopersicum) is a climacteric fruit whose ripening is characterized by sequential changes in protein expression, resulting in different profiling of polypeptide bands at each maturity stage. However fruits from diverse tomato genotypes vary in their ripening. Heterosis is the outstanding performance of heterozygous genotypes compared to their homozygous parents. Though this term has been currently applied to quantitative traits, it could be extended to qualitative and dichotomic attributes, hence new statistical and bioinformatic approaches must be developed or adapted to analyze heterosis for traits such as polypeptide profiles. Permutational Manova (PM) -formerly ?nonparametric manova?- is a Permutational Multivariate Analysis of Variance that uses distance matrices. It is non-parametric method, based on permutation test with pseudo-F ratios. It is an alternative to traditional multivariate analysis of variance (MANOVA) that is too stringent in their assumptions for most ecological (and also genetic) multivariate data sets. Typical uses of this method include analysis of ecological community data or genetic data where we might have a limited number of samples of individuals and thousands or millions of columns of gene expression data. PM is further an alternative to AMOVA (analysis of molecular variance). The aim of this study was to compare the polypeptide profiles of pure lines and hybrids tomato fruit in four different maturity stages of tomato fruit ripening in order to detect putative heterosis involved in their genetic determination, and its eventual associations with phenotypic traits. Fruits from 15 genotypes (five Recombinant Inbred Lines -RIL, selected for fruit weight and shelf life- and their ten diallel Second Cycle Hybrids -SCH-) were screened by SDS-PAGE for 25 polypeptide bands at 4 maturity stages: Mature Green (MG), Breaker (B), Mature Red attached to plant (MRa) and Mature Red in shelves (MRs) according to standard techniques. A database of 15 x 25 x 4 dimension was analyzed by multivariate PM. Single effects of genotype condition (homozygote vs. heterozygote), fruit weight and shelf life, and their double and triple interactions on polypeptide profiles at all maturity stages and discriminating by stage, were evaluated through PM, using the Bray?s distance. The Software Statistical R (v. 3.1.1) was applied for statistical analyses. PM was computed by the "adonis" function within the package "vegan" of R. All tests were performed at a significance level of 5%, the number of permutations being 100 and 1000 in all cases. Applying 100 permutations, genotype condition was the only significant effect (p = 0.04) on polypeptide profiles when all maturity stages were jointly analyzed, this indicating heterosis because heterozygotes were different from homozygotes. Effects of fruit weight, shelf life, and their double and triple interactions were non significant (p = 0.45, p = 0.76, p = 0.47, p = 0.38, p = 0.75, and p = 0.97, respectively). When dscriminating among maturity stage, genotype condition was the only significant effect in MRa (p = 0.04) but it was non significant in the other stages (MG, B, and MRs). Therefore the double interaction genotype condition x shelf life was significant (p = 0.03) for polypeptide profiles at MG. Statistical sensibility of PM was tested by increasing the number of permutations to 1000 but the same results were obtained, this evidencing the robustness of the analysis. PM detected significant heterosis for tomato fruit polypeptide profiles during ripening, specifically at MRa, which could be explained because of tomato is consumed at this stage. Hence the detected heterosis could be due to artificial selection practiced by breeders to obtain an acceptable fruit quality acceptable to consumers and would have important consequences in designing new breeding strategies. Also fruit weight was not associated to polypeptide profiles but fruit shelf life had a significant interaction with genotype condition on heterosis for polypeptide profiles at MG. This interaction suggests that differences in fruit shelf life among homozygous and heterozygous genotypes could be associated with presence / absence of at least some polypeptide bands in the early maturity stage MG. (Selected for oral presentation)