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Abstract Detail

Population Genetics/Genomics

Ranathunge, Chathurani [1], Wheeler, Gregory [2], Chimahusky, Melody [3], Perkins, Andy [4], Welch, Mark [3].

Of evolutionary tuning knobs: Microsatellites as drivers of adaptive evolution in common sunflower.

The mechanisms by which natural populations rapidly adapt to their local environments are not completely understood. One such proposed mechanism, the tuning knob model, predicts that stepwise changes in microsatellite allele length can lead to stepwise effects on phenotypes. To test the predictions of the tuning knob model, we estimated the effect of microsatellite allele length on heritable phenotypic variation at the level of gene expression with natural populations of the common sunflower (Helianthus annuus L.). Seeds collected from six populations at two distinct latitudes in Kansas and Oklahoma were planted and grown in a common garden. An RNA-Seq experiment was conducted with 95 of these individuals. Of the 3325 microsatellites genotyped using the RNA-Seq data, 479 showed significant correlation between allele length and gene expression (hereafter termed eSTRs). The majority (70.4%) of eSTRs were located within the untranslated regions (UTRs) which suggests that they are well positioned to function as cis-regulatory elements. A subset of these eSTRs were then used in a population genetic study involving 672 individuals from 17 sunflower populations across a wider latitudinal range from Saskatchewan to Oklahoma. Signatures of strong directional selection on eSTRs compared to neutrally evolving anonymous microsatellites were detected. This suggests that shorter or longer allele lengths at the eSTRs are favored in even more extreme environments. This study provides compelling evidence that a substantial number of transcribed microsatellites can rapidly generate heritable and potentially adaptive genetic variation.

1 - Mississippi State University, Biological Sciences, 219 Harned Hall, 295 Lee Blvd, Mississippi State, Starkville, MS, 39762, United States
2 - Ohio State University, Evolution, Ecology, and Organismal Biology
3 - Mississippi State University, Biological Sciences, 219 Harned Hall, 295 Lee Blvd, Starkville, MS, 39762, United States
4 - Mississippi State University, Computer Science and Engineering, Starkville, Mississippi, 39762, United States

Keywords:
microsatellites
Sunflower
Asteraceae
Helianthus
Adaptation.

Presentation Type: Oral Paper
Session: 38, Population Genetics and Genomics I
Location: 101/Mayo Civic Center
Date: Wednesday, July 25th, 2018
Time: 11:30 AM
Number: 38014
Abstract ID:488
Candidate for Awards:Margaret Menzel Award