RESUMO
We compared the genetic architecture of thirteen maize morphological traits in a large population of recombinant inbred lines. Four traits from the male inflorescence (tassel) and three traits from the female inflorescence (ear) were measured and studied using linkage and genome-wide association analyses and compared to three flowering and three leaf traits previously studied in the same population. Inflorescence loci have larger effects than flowering and leaf loci, and ear effects are larger than tassel effects. Ear trait models also have lower predictive ability than tassel, flowering, or leaf trait models. Pleiotropic loci were identified that control elongation of ear and tassel, consistent with their common developmental origin. For these pleiotropic loci, the ear effects are larger than tassel effects even though the same causal polymorphisms are likely involved. This implies that the observed differences in genetic architecture are not due to distinct features of the underlying polymorphisms. Our results support the hypothesis that genetic architecture is a function of trait stability over evolutionary time, since the traits that changed most during the relatively recent domestication of maize have the largest effects.
Assuntos
Flores/genética , Inflorescência/genética , Folhas de Planta/genética , Locos de Características Quantitativas/genética , Zea mays/genética , Evolução Biológica , Mapeamento Cromossômico , Cruzamentos Genéticos , Ligação Genética , Pleiotropia Genética , Estudo de Associação Genômica Ampla , Fenótipo , Polimorfismo de Nucleotídeo Único , Caracteres Sexuais , Zea mays/anatomia & histologiaRESUMO
Flowering time is a complex trait that controls adaptation of plants to their local environment in the outcrossing species Zea mays (maize). We dissected variation for flowering time with a set of 5000 recombinant inbred lines (maize Nested Association Mapping population, NAM). Nearly a million plants were assayed in eight environments but showed no evidence for any single large-effect quantitative trait loci (QTLs). Instead, we identified evidence for numerous small-effect QTLs shared among families; however, allelic effects differ across founder lines. We identified no individual QTLs at which allelic effects are determined by geographic origin or large effects for epistasis or environmental interactions. Thus, a simple additive model accurately predicts flowering time for maize, in contrast to the genetic architecture observed in the selfing plant species rice and Arabidopsis.
Assuntos
Flores/genética , Locos de Características Quantitativas , Zea mays/genética , Alelos , Mapeamento Cromossômico , Cromossomos de Plantas/genética , Epistasia Genética , Flores/crescimento & desenvolvimento , Frequência do Gene , Genes de Plantas , Variação Genética , Geografia , Endogamia , Fenótipo , Polimorfismo de Nucleotídeo Único , Característica Quantitativa Herdável , Recombinação Genética , Fatores de Tempo , Zea mays/crescimento & desenvolvimento , Zea mays/fisiologiaRESUMO
We characterized allelic variation at barren inflorescence2 (bif2), a maize co-ortholog of the Arabidopsis PINOID protein kinase (PID), and tested for trait associations with bif2 in both an association mapping population of 277 diverse maize inbreds and in the inter-mated B73 x Mo17 (IBM) linkage population. Results from the quantitative analyses were compared with previous reports of bif2 phenotypes in mutagenesis studies. All three approaches (association, linkage, and mutagenesis) detect a significant effect of bif2 on tassel architecture. Association mapping implicates bif2 in an unexpectedly wide range of traits including plant height, node number, leaf length, and flowering time. Linkage mapping finds a significant interaction effect for node number between bif2 and other loci, in keeping with previous reports that bif2;spi1 and Bif2;Bif1 double mutants produce fewer phytomers. The Mo17 allele is associated with a reduced tassel branch zone and shows lower expression than the B73 allele in hybrid B73-Mo17 F(1) inflorescences, consistent with the complete absence of tassel branches in the bif2 knockout mutant. Overall, these data suggest that allelic variation at bif2 affects maize architecture by modulating auxin transport during vegetative and inflorescence development.
