The genetic basis for natural variation in heteroblasty in Antirrhinum

Abstract

SummaryHeteroblasty refers to the changes in leaf shape and size (allometry) along stems. Although evolutionary changes involving heteroblasty might contribute to leaf diversity, little is known of the extent to which heteroblasty differs between species or how it might relate to other aspects of allometry or other developmental transitions.Here, we develop a computational model that can quantify differences in leaf allometry between Antirrhinum (snapdragon) species, including variation in heteroblasty. It allows the underlying genes to be mapped in inter-species hybrids, and their effects to be studied in similar genetic backgrounds.Heteroblasty correlates with overall variation in leaf allometry, so species with smaller, rounder leaves produce their largest leaves earlier in development. This involves genes that affect both characters together and is exaggerated by additional genes with multiplicative effects on leaf size. A further heteroblasty gene also alters leaf spacing, but none affect other developmental transitions, including flowering.We suggest that differences in heteroblasty have co-evolved with overall leaf shape and size in Antirrhinum because these characters are constrained by common underlying genes. By contrast, heteroblasty is not correlated with other developmental transitions, with the exception of internode length, suggesting independent genetic control and evolution.

Heterochrony underpins natural variation inCardamine hirsutaleaf form

“…Similar examples were reported as early as 1944 in cotton (54,55), where early flowering genotypes developed leaves with increased complexity, and our work provides a framework to interpret these results from diverse taxa. However, heteroblasty can be uncoupled from reproduction in other examples (56), and early flowering can be associated with decreased, rather that increased, leaf complexity (57). Therefore, the timekeeping activity of common genetic modules may tend to associate flowering time with the rate of progression of vegetative development, but whether and how this tendency is expressed in different species may depend on the interplay of these timekeeping modules with lineagespecific leaf developmental programs, ecological challenges, reproductive strategies, and drift.…”

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).…”

Revealing plant cryptotypes: defining meaningful phenotypes among infinite traits

“…Pseudo-landmarks in snapdragon (Antirrhihum majus) describe cryptotypes that define shape attributes most varying by allometry (shape variability correlated with size) [11], mutation [12], heteroblasty (the changes in leaves arising from successive nodes) [13], and evolution [14 ].…”