Cryptic Patterning of Avian Skin Confers a Developmental Facility for Loss of Neck Feathering

147

Significance How body pattern evolves in nature remains largely unknown. Although recent progress has been made on the molecular basis of losing morphological features during adaptation to new environments (regressive evolution), there are few well worked out examples of how morphological features may be gained in natural species (constructive evolution). Here we use genetic crosses to study how threespine stickleback fish have increased their tooth number in a new freshwater environment. Genetic mapping and gene expression experiments suggest regulatory changes have occurred in the gene for a bone morphogenetic signaling molecule, leading to increased expression in the freshwater fish that have more teeth. Our studies suggest that changes in gene regulation may underlie both gain and loss traits during vertebrate evolution.

Section: Discussionmentioning

confidence: 99%

Evolved tooth gain in sticklebacks is associated with acis-regulatory allele ofBmp6

Cleves

Ellis

Jimenez

et al. 2014

147

“…There a stability change might result from a particular gene being expressed during development (e.g., ref. 33), which would correspond to an abrupt change in the parameter values in a mathematical model. Alternatively a uniform state might be stable in an embryo that is too small to permit the destabilizing frequencies, but becomes unstable as the embryo grows (e.g., ref.…”

Section: Pattern Generation From Uniform Vegetationmentioning

confidence: 99%

Using wavelength and slope to infer the historical origin of semiarid vegetation bands

Sherratt

2015

Landscape-scale patterns of vegetation occur worldwide at interfaces between semiarid and arid climates. They are important as potential indicators of climate change and imminent regime shifts and are widely thought to arise from positive feedback between vegetation and infiltration of rainwater. On gentle slopes the typical pattern form is bands (stripes), oriented parallel to the contours, and their wavelength is probably the most accessible statistic for vegetation patterns. Recent field studies have found an inverse correlation between pattern wavelength and slope, in apparent contradiction with the predictions of mathematical models. Here I show that this “contradiction” is based on a flawed approach to calculating the wavelength in models. When pattern generation is considered in detail, the theory is fully consistent with empirical results. For realistic parameters, degradation of uniform vegetation generates patterns whose wavelength increases with slope, whereas colonization of bare ground gives the opposite trend. Therefore, the empirical finding of an inverse relationship can be used, in conjunction with climate records, to infer the historical origin of the patterns. Specifically, for the African Sahel my results suggest that banded vegetation originated by the colonization of bare ground during circa 1760–1790 or since circa 1850.

“…Hair, feathers, glands, teeth, taste buds, and intestinal crypt villi are similarly induced under the direction of epithelial and mesenchymal interactions. Similar reaction-diffusion models have been proposed to control the size and spacing of manifold placode-derived organs (3), such as hair (4), feathers (5), and teeth (6). Activators and inhibitors in the bone morphogenetic protein (BMP), fibroblast growth factor (FGF), Hedgehog (Hh), and Wingless (Wnt) pathways execute the pattern.…”

mentioning

confidence: 99%

Coevolutionary patterning of teeth and taste buds

Bloomquist

Parnell

Phillips

et al. 2015

Teeth and taste buds are iteratively patterned structures that line the oro-pharynx of vertebrates. Biologists do not fully understand how teeth and taste buds develop from undifferentiated epithelium or how variation in organ density is regulated. These organs are typically studied independently because of their separate anatomical location in mammals: teeth on the jaw margin and taste buds on the tongue. However, in many aquatic animals like bony fishes, teeth and taste buds are colocalized one next to the other. Using genetic mapping in cichlid fishes, we identified shared loci controlling a positive correlation between tooth and taste bud densities. Genome intervals contained candidate genes expressed in tooth and taste bud fields. sfrp5 and bmper, notable for roles in Wingless (Wnt) and bone morphogenetic protein (BMP) signaling, were differentially expressed across cichlid species with divergent tooth and taste bud density, and were expressed in the development of both organs in mice. Synexpression analysis and chemical manipulation of Wnt, BMP, and Hedgehog (Hh) pathways suggest that a common cichlid oral lamina is competent to form teeth or taste buds. Wnt signaling couples tooth and taste bud density and BMP and Hh mediate distinct organ identity. Synthesizing data from fish and mouse, we suggest that the Wnt-BMP-Hh regulatory hierarchy that configures teeth and taste buds on mammalian jaws and tongues may be an evolutionary remnant inherited from ancestors wherein these organs were copatterned from common epithelium.quantitative trait loci | tooth/taste bud development | placode patterning | bipotency | plasticity