Evolution of Allometry inAntirrhinum   

Abstract

Correlated variation in shape and size (allometry) is a major component of natural diversity. We examined the evolutionary and genetic basis for allometry using leaves and flower petals of snapdragon species (Antirrhinum). A computational method was developed to capture shape and size variation in both types of organ within the Antirrhinum species group. The results show that the major component of variation between species involves positively correlated changes in leaf and petal size. The correlation was maintained in an F2 population derived from crossing two species with organs of different sizes, suggesting that developmental constraints were involved. Identification of the underlying genes as quantitative trait loci revealed that the larger species carried alleles that increased organ size at all loci. Although this was initially taken as evidence that directional selection has driven diversity in both leaf and petal size, simulations revealed that evolution without consistent directional selection, an undirected walk, could also account for the parental distribution of organ size alleles.

Genetic Dissection of Leaf Development in Brassica rapa Using a Genetical Genomics Approach

“…S4, U and V). In this paper, we do not address heteroblasty, which refers to changes in leaf shape and size (allometry) along stems (Feng et al, 2009;Costa et al, 2012). Leaf shape and size do vary with increasing leaf number; however, we chose for this study the third leaf, which in shape resembles the next leaves, while the first and second leaves are often asymmetric and smaller.…”

“…Duplicated genes are of major importance for evolutionary novelty, since they can contribute to functional innovation by mutation of their coding sequences, expression divergence, and rewiring regulatory networks through variation in interactions among different orthologs (Gaeta et al, 2007;Liu and Adams, 2007;De Smet and Van de Peer, 2012). Several studies have correlated variation in gene expression or the fate of duplicated genes to phenotypic diversity, such as flowering time (Ft) variation, leaf shape, size, and numbers, pest resistance, and stress tolerance in eukaryotes (Gaeta et al, 2007;Hovav et al, 2008;Feng et al, 2009;Whittle and Krochko, 2009;Combes et al, 2012;Costa et al, 2012;Xiao et al, 2013).…”

A Genetic Framework for Grain Size and Shape Variation in Wheat

“…To further substantiate this, QTL analysis was performed on the principal components (i.e., PC1 and PC2) extracted from each DH population ( Figure 2). Similar approaches have been used before for the study of organ morphology in other species (Langlade et al, 2005;Feng et al, 2009).…”

Multiscale quantification of morphodynamics: MorphoLeaf, software for 2-D shape analysis

“…Then, we performed a principal component analysis (PCA) to analyse variations in tooth shape (Fig. 3A,B) as previously described for the whole leaf contours (Langlade et al, 2005;Bensmihen et al, 2008;Feng et al, 2009;Chitwood et al, 2014). The first axis corresponds to the variation in tooth height and confirms the difference in pointedness observed between tooth 1 and teeth 2 and 3.…”

“…Discretisation of shape based on evenly spaced marks along the contour and averaging these marks over many leaves allows the proper description and quantification of simple entire leaves (Langlade et al, 2005;Bensmihen et al, 2008;Weight et al, 2008;Feng et al, 2009). Likewise, landmark-independent Fourierbased analysis of the contour is useful to quantify the general shape of the leaf (Chitwood et al, 2012(Chitwood et al, , 2013(Chitwood et al, , 2014.…”