lunes, 25 de abril de 2016

Transcriptomes reveal the genetic mechanisms underlying ionic regulatory adaptations to salt in the crab-eating frog.

Seleccionado por: Ruth 

Abstract

The crab-eating frog, Fejervarya cancrivora, is the only frog that lives near seas. It tolerates increasedenvironmental concentrations of sodium, chloride and potassium partly by raising ion and urea levels in its blood plasma. The molecular mechanism of the adaptation remains rarely documented. Herein, we analyze transcriptomes of the crab-eating frog and its closely related saline-intolerant species, F. limnocharis, to explore the molecular basis of adaptations to such extreme environmental conditions. Analyses reveal the potential genetic mechanism underlying the adaptation to salinity for the crabeating frog. Genes in categories associated with ion transport appear to have evolved rapidly in F. cancrivora. Both positively selected and differentially expressed genes exhibit enrichment in the GO category regulation of renal sodium excretion. In this category, the positively selected sites of ANPEP and AVPR2 encode CD13 and V2 receptors, respectively; they fall precisely on conserved domains. More differentially expressed rapidly evolved genes occur in the kidney of F. cancrivora than in F. limnocharis. Four genes involved in the regulation of body fluid levels show signs of positive selection and increased expression. Significant up-regulation occurs in several genes of F. cancrivora associated with renin-angiotensin system and aldosterone-regulated sodium reabsorption pathways, which relate to osmotic regulation.


En el  artículo se trata de explicar las adaptaciones genéticas de una ranita a ambientes salobres, mediante la identificación de perfiles de expresión para genes candidatos implicados en la adaptación a estos ambientes. Este artículo es de mi interés dada la naturaleza de mi trabajo, donde planteo estudiar salamandras que aparentemente se han adaptado a ambientes más secos comparadas con sus especies hermanas que habitan en ambientes húmedos y utilizando ahora estas herramientas (transcriptoma) es posible identificar genes candidatos a selección.

lunes, 11 de abril de 2016

Non-adaptive plasticity potentiates rapid adaptive evolution of gene expression in nature

Ghalambor CK, Hoke KL, Ruell EW et al. (2015) Non-adaptive plasticity potentiates rapid adaptive evolution of gene expression in nature. Nature, 525, 372–375.


Seleccionado por: Azalea

Abstract
 Phenotypic plasticity is the capacity for an individual genotype to produce different phenotypes in response to environmental variation1. Most traits are plastic, but the degree to which plasticity is adaptive or non-adaptive depends on whether environmentally induced phenotypes are closer or further away from the local optimum2, 3, 4. Existing theories make conflicting predictions about whether plasticity constrains or facilitates adaptive evolution4, 5, 6, 7, 8, 9, 10, 11, 12. Debate persists because few empirical studies have tested the relationship between initial plasticity and subsequent adaptive evolution in natural populations. Here we show that the direction of plasticity in gene expression is generally opposite to the direction of adaptive evolution. We experimentally transplanted Trinidadian guppies (Poecilia reticulata) adapted to living with cichlid predators to cichlid-free streams, and tested for evolutionary divergence in brain gene expression patterns after three to four generations. We find 135 transcripts that evolved parallel changes in expression within the replicated introduction populations. These changes are in the same direction exhibited in a native cichlid-free population, suggesting rapid adaptive evolution. We find 89% of these transcripts exhibited non-adaptive plastic changes in expression when the source population was reared in the absence of predators, as they are in the opposite direction to the evolved changes. By contrast, the remaining transcripts exhibiting adaptive plasticity show reduced population divergence. Furthermore, the most plastic transcripts in the source population evolved reduced plasticity in the introduction populations, suggesting strong selection against non-adaptive plasticity. These results support models predicting that adaptive plasticity constrains evolution6, 7, 8, whereas non-adaptive plasticity potentiates evolution by increasing the strength of directional selection11, 12. The role of non-adaptive plasticity in evolution has received relatively little attention; however, our results suggest that it may be an important mechanism that predicts evolutionary responses to new environments.

Quizá debido a la naturaleza de los proyectos que la mayoría de nosotros estamos desarrollando, pocas veces nos preguntamos cómo la plasticidad fenotípica está afectando la trayectoria evolutiva de las especies. Más allá de modelos teóricos, parece que se ha estudiado relativamente poco cómo la plasticidad puede influir en la intensidad de la selección. En el artículo, usando como modelo al pez guppy y un diseño experimental que me pareció muy ingenioso, muestran que la plasticidad, al menos en este caso, NO favorece a una rápida evolución adaptativa.