Heterochronic genes in plant evolution and development

Abstract

Evolution of morphology includes evolutionary shifts of developmental processes in space or in time. Heterochronic evolution is defined as a temporal shift. The concept of heterochrony has been very rewarding to investigators of both animal and plant developmental evolution, because it has strong explanatory power when trying to understand morphological diversity. While for animals, extensive literature on heterochrony developed along with the field of evolution of development, in plants the concept has been applied less often and is less elaborately developed. Yet novel genetic findings highlight heterochrony as a developmental and evolutionary process in plants. Similar to what has been found for the worm Caenorhabditis, a heterochronic gene pathway controlling developmental timing has been elucidated in flowering plants. Two antagonistic microRNA’s miR156 and miR172 target two gene families of transcription factors, SQUAMOSA PROMOTOR BINDING PROTEIN-LIKE and APETALA2-like, respectively. Here, we propose that this finding now allows the molecular investigation of cases of heterochronic evolution in plants. We illustrate this point by examining microRNA expression patterns in the Antirrhinum majus incomposita and choripetala heterochronic mutants. Some of the more beautiful putative cases of heterochronic evolution can be found outside flowering plants, but little is known about the extent of conservation of this flowering plant pathway in other land plants. We show that the expression of an APETALA2-like gene decreases with age in a fern species. This contributes to the idea that ferns share some heterochronic gene functions with flowering plants.

The Arabidopsis Mediator CDK8 module genes CCT (MED12) and GCT (MED13) are global regulators of developmental phase transitions

“…For example, it is hypothesized that an extended phase of rapid brain growth (a characteristic of juvenile development) played a key role in the evolution of humans from their primate ancestors (Gould, 1977). In flowering plants, changes in the relative timing of juvenile and adult development can have major effects on traits such as leaf morphology and the onset of flowering (reviewed by Huijser and Schmid, 2011;Geuten and Coenen, 2013;Poethig, 2013). Resistance to herbivory, as well as changes in cell wall composition, also have an important temporal component (Abedon et al, 2006; reviewed by Boege andMarquis, 2005 andChandler et al, 2011).…”

Plastic expression of heterochrony quantitative trait loci (hQTLs) for leaf growth in the common bean (Phaseolus vulgaris)

“…These results showed that the h QTL functional mapping model can reveal more intricate details of environmental responses of dynamic traits such as leaf growth, or any other similar trait. These results also show the dynamic complexity of growth and developmental mechanisms plant can use for adaptation to different environments (Geuten & Coenen, 2013). Heterochrony genes control precisely timed switches for developmental transitions, and provide in this way a time dimension to developmental regulation (Moss, 2007;Geuten & Coenen, 2013).…”

“…These results also show the dynamic complexity of growth and developmental mechanisms plant can use for adaptation to different environments (Geuten & Coenen, 2013). Heterochrony genes control precisely timed switches for developmental transitions, and provide in this way a time dimension to developmental regulation (Moss, 2007;Geuten & Coenen, 2013). Some heterochrony genes may possess homologs in other species.…”

A History of Genomic Structures: The Big Picture

“…When miR156 levels decline, the level of SPL proteins increases, miR172 is activated, fl owering genes are activated, and adult leaf features are induced. When miR172 levels are increasing, the APETALA2-like ( AP2-like ) genes are progressively silenced and adult leaf traits as well as fl owering are induced (see in Geuten and Coenen 2013 ). More miRNAs are being described as important players in plant development as expected from their early evolution (Fig.…”

“…The total number of Hox genes found among plant genomes refl ects the complex patterns of genome duplication and gene duplication or loss that have characterized the evolutionary histories of these species and the higher developmental and organizational complexity in angiosperms than in mosses and unicellular algae (Mukherjee et al 2009 ). In contrast to animals, plants entail the continuous development of new organs as time progresses (Geuten and Coenen 2013 ) (Friedman et al 2004 ). (v) Flowers .…”