Plasticity in gene expression underlies much of the ability of organisms to cope with environmental variation. Understanding limits in the ability of organisms to adjust to a range of environments has implications for understanding how pathogens respond to human environments (e.g., antibiotic resistance), and how humans respond, at times inappropriately, to current environments (e.g., obesity). This research tests the hypothesis that the degree of modularity, or environmental specificity, of gene expression has fundamental implications for defining limits in the evolution of plasticity. Highly modular gene expression is assumed to permit adaptation to specific environments because overlap in gene function, and thus pleiotropy, is much reduced. At the same time, highly modular gene expression comes at a potential cost: when alternative environments are experienced infrequently, selection on environment-specific genes is weakened and mutation accumulation can occur. These hypotheses will be tested in a newly emerging model system in evolutionary developmental genetics: homed beetles in the genus Onthophagus. These insects display highly divergent alternative phenotypes depending on larval nutrition. Such alternative morphs develop through expression of genes shared across the development of traits, as well as genes specific to different morphs. This research tests several predictions by contrasting the development of secondary sexual traits (horns) and brains in horned (aggressive fighter) and hornless (non-aggressive sneaker) beetle morphs. This research tests four predictions both within and between species: 1) increased environmentally-specific gene expression will be correlated with the evolution of greater ranges of plasticity, 2) genes specific to the development of morph behavior and morphology will be more genetically variable than those shared between morphs, 3) genes specific to morph development experience higher rates of genetic divergence as a result of weak selection, and 4) morph-specific genes will play functional roles in generating divergence between morphs. This work will use a variety of tools developed for Onthophagus beetles, including transcriptional profiling via microarray analysis, and investigating gene function through RNA interference gene knock-down. Relevance. Understanding evolutionary limits of plasticity in gene expression has implications for public health. If we can curb the ability of pathogens to cope with multiple environments, such as invading the human body or dealing with multiple medications, we may be able to reduce pathogen virulence. We may learn why humans cannot express genes that promote health in a wide range of environments, such as diabetes-inducing nutritional environments or changes in the aging brain. ? ? ?

Agency
National Institute of Health (NIH)
Institute
National Institute of General Medical Sciences (NIGMS)
Type
Postdoctoral Individual National Research Service Award (F32)
Project #
1F32GM083830-01
Application #
7405887
Study Section
Special Emphasis Panel (ZRG1-F08-G (20))
Program Officer
Haynes, Susan R
Project Start
2008-01-01
Project End
2009-12-31
Budget Start
2008-01-01
Budget End
2008-12-31
Support Year
1
Fiscal Year
2008
Total Cost
$44,846
Indirect Cost
Name
Indiana University Bloomington
Department
Biology
Type
Schools of Arts and Sciences
DUNS #
006046700
City
Bloomington
State
IN
Country
United States
Zip Code
47401
Kijimoto, Teiya; Snell-Rood, Emilie C; Pespeni, Melissa H et al. (2014) The nutritionally responsive transcriptome of the polyphenic beetle Onthophagus taurus and the importance of sexual dimorphism and body region. Proc Biol Sci 281:
Snell-Rood, Emilie C; Troth, Ashley; Moczek, Armin P (2013) DNA methylation as a mechanism of nutritional plasticity: limited support from horned beetles. J Exp Zool B Mol Dev Evol 320:22-34
Snell-Rood, Emilie C; Moczek, Armin P (2012) Insulin signaling as a mechanism underlying developmental plasticity: the role of FOXO in a nutritional polyphenism. PLoS One 7:e34857
Snell-Rood, Emilie C; Cash, Amy; Han, Mira V et al. (2011) Developmental decoupling of alternative phenotypes: insights from the transcriptomes of horn-polyphenic beetles. Evolution 65:231-45
Snell-Rood, Emilie C; Van Dyken, James David; Cruickshank, Tami et al. (2010) Toward a population genetic framework of developmental evolution: the costs, limits, and consequences of phenotypic plasticity. Bioessays 32:71-81
Choi, Jeong-Hyeon; Kijimoto, Teiya; Snell-Rood, Emilie et al. (2010) Gene discovery in the horned beetle Onthophagus taurus. BMC Genomics 11:703