News article excerpt:
“This is the first experiment to show that natural variation in the expression of a microRNA can lead to a change in the appearance of an organism. MicroRNAs can fine-tune the level at which genes are expressed, so evolutionary changes in the production of microRNA would be an elegant way to cause morphological changes.”
RE: Surprising new function for small RNAs in evolution Posted: 19 Apr 2013 04:59 AM PDT Scientists have discovered a completely new mechanism by which evolution can change the appearance of an organism. The researchers found that the number of hairs on flies’ legs varies according to the level of activity of a so-called microRNA. The results shed a completely new light on the molecular mechanisms of evolution.
My comment: The results do not shed a completely new light on the molecular mechanisms of evolution and this news would probably not surprise anyone who is familiar with the basic principles of biology or levels of biological organization required to link sensory cause to epigenetic effects on morphogenesis. For example, I modeled effects on morphogenesis in the context of Nutrient-dependent / Pheromone-controlled Adaptive Evolution after it became obvious that the effects on morphogenesis were due to nutrient-dependent changes in the thermodynamics of intracellular signaling that showed up in phenotypes due to their association with organism-level thermoregulation. After that, I used examples across species in Nutrient-dependent / Pheromone-controlled thermodynamics and thermoregulation to make my point perfectly clear.
Cause and effect is exemplified in species from microbes to man, but these additional results from flies make a nice addition to the extant literature. Also, flies may best exemplify how adaptive evolution occurs via niche construction because the molecular mechanisms of their nutrient-dependent social behavior and their sexual behavior have been well-detailed.
For contrast, evolutionary theorists have, until recently, been touting random mutations as the cause of morphological variation. They may now need to start touting my model of nutrient-dependent changes in the microRNA / messenger RNA balance, which are responsible for ecological, social, neurogenic, and socio-cognitive niche construction. That’s because none of these required levels of niche construction would be possible if the microRNA / messenger RNA balance did not also control morphogenesis. We see this cause and effect, for example, from the advent of nutrient-dependent pheromone-controlled sexual reproduction in yeasts. It would be inconsistent with what is known about adaptive evolution if we did not see the effect on morphogenesis in flies.
For consistency in an acurate representation of cause and effect, see also: Nutrient-dependent / Pheromone-controlled Adaptive Evolution
“This model of systems biology represents the conservation of bottom-up organization and top-down activation via:
Nutrient stress-induced and social stress-induced intracellular changes in the microRNA (miRNA) / messenger RNA (mRNA) balance;
Intermolecular changes in DNA (genes) and alternative splicing;
Non-random experience-dependent stochastic variations in de novo gene expression and biosynthesis of odor receptors;
The required gene-cell-tissue-organ-organ system pathway that links sensory input directly to gene activation in neurosecretory cells and to miRNA-facilitated learning and memory in the amygdala of the adaptively evolved mammalian brain;
The required reciprocity that links gene expression to behavior that alters gene expression (i.e., reciprocity from genes to behavior and back) in model organisms like the honeybee.”