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A Chemical Screening Procedure for Glucocorticoid Signaling with a Zebrafish Larva Luciferase Reporter System
Published on: September 10, 2013
Evidence for a divergence in function between two glucocorticoid receptors from a basal teleost
Yi Li1, Armin Sturm, Phil Cunningham
1Nutritional Sciences Research Division, King's College London, Franklin Wilkins Building, 150 Stamford Street, London SE1 9NH, UK.
BMC Evolutionary Biology
|August 7, 2012
Summary
Duplicate glucocorticoid receptors (GRs) in fish may have evolved through subfunctionalization, with distinct DNA-binding domains potentially driving retention. This study investigated GR evolution in basal ray-finned fish to understand the advantage of duplicated GRs.
Area of Science:
- Evolutionary biology
- Molecular biology
- Genomics
Background:
- Most teleost fish possess duplicated glucocorticoid receptors (GRs), but the evolutionary advantage remains unclear.
- Functional differences between GR subtypes have not been defined, hindering understanding of GR duplication retention.
Purpose of the Study:
- To investigate the evolutionary factors driving the retention of duplicate GRs in teleosts.
- To examine GRs in Acipenser ruthenus (pre-WGD) and Pantodon buchholzi (post-WGD) to understand GR evolution across the teleost whole genome duplication (WGD) event.
Main Methods:
- Phylogenetic analyses of GR genes from A. ruthenus and P. buchholzi.
- Identification and characterization of GR sequences and splice variants.
- In vitro transactivation assays to assess hormone sensitivity and activity of different GRs.
Main Results:
- A. ruthenus possesses a single GR (ArGR), while P. buchholzi has two (PbGR1, PbGR2).
- Phylogenetic analysis reveals ArGR branches separately from teleost GRs, with teleost GRs splitting into two sublineages.
- PbGR2 has a splice variant (PbGR2b) lacking a 9-amino acid insert found in ArGR, PbGR1, and teleost GR1, but not GR2, indicating differential DNA-binding domain structures.
Conclusions:
- Functional differences in transactivation sensitivity between PbGR1 and PbGR2b suggest early divergence of paralog functions in teleosts.
- The retention of duplicated GRs may be explained by subfunctionalization and gene sharing.
- The evolution of distinct DNA-binding domain structures, including a 9-amino acid insert and its subsequent loss in some teleost GR2, indicates selection for receptors with altered DNA-binding properties.
