November 3 2016

5:00 pm 1100 TLSB

EcoEvoPub Series

Graduate Student Presentations


Devaleena S. Pradhan
Department of Integrative Biology and Physiology, UCLA

"Preparing for the long haul: androgen signaling in the muscle of a migratory songbird"

In preparation for long-distance migration, birds dramatically modify major aspects of their anatomy, physiology and behavior. Prior to migration, Gambels White-crowned Sparrows \(WCS\) become hyperphagic, accumulate lipid stores, gain weight, and increase the fiber size of the pectoralis \(flight\) but not gastrocnemius \(leg\) muscles. Mechanisms regulating muscle fiber hypertrophy are unknown, but androgens, which are anabolic, might be involved. Given that plasma testosterone \(T\) and 5-dihydrotestosterone \(5-DHT\) levels are basal at the onset of migration, we hypothesized that local androgen signaling within muscle stimulates flight muscle hypertrophy prior to migration. As a test, local T levels as well as mRNA expression levels of androgen receptor \(AR\) and 5-reductase Type 1 \(converts T to 5-DHT\) were examined in male WCS muscles across three stages of migratory preparedness: Winter \(February\), Prenuptial molt \(March\), and Spring departure \(April\). Over the course of this experiment, T levels were low and generally invariant in plasma and muscles. Importantly, however, some T was detected in muscles at each stage of migratory preparedness. Interestingly, in both muscles, AR and 5-reductase Type 1 increased dramatically at departure compared to previous stages. Finally, mRNA expression of insulin-like growth factor 1, an androgen-dependent gene involved in muscle growth, also increased at Spring departure in the pectoralis. Thus increased synthesis of 5-DHT as well as AR expression may enable muscle to utilize existing androgenic substrate to activate AR-dependent anabolic properties in preparation for migration. These data suggest that hypertrophy of flight muscles are especially susceptible to this enhanced androgenic signaling to promote increased endurance and power for long distance flight.

Tiffany Armenta
Department of Ecology and Evolutionary Biology, UCLA

Does gene expression change to prepare animals for dispersal

Dispersal from the natal territory is an important life-history trait. It is energetically costly and risky, yet it is often necessary to avoid interspecific conflict and inbreeding. In female yellow-bellied marmots, dispersal supports the social cohesion hypothesis: more socially integrated females are less likely to disperse. In males, dispersal can be influenced by social group size. Given that the social environment can predict dispersal, do individuals anticipate and prepare for dispersal physiologically? To answer this, we did whole genome sequencing of RNA (RNA-Seq) from the blood of 77 yearling marmots prior to the timing of dispersal. We observed marmot colonies daily to assess if and when an animal dispersed from its natal territory. Since dispersal is an energetically costly endeavor that may result in interactions with new conspecifics, we expected to see increased gene expression activity in metabolic and immunological pathways in dispersers compared to those that remained at the natal site. Here I will compare and contrast results from three methods commonly used in RNA-Seq analyses.











































































































































































































































































































































































































































































































































































































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