Abstract Detail

Classical Genetics

Hawkins, Angela [1], Garza, Elyssa [1], Pepper, Alan [2].

Molecular signatures of selection, drift, introgression, and gene duplication in the serpentine endemic plant Caulanthus amplexicaulis var. barbarae (Brassicaceae).

Serpentine endemic plants are excellent models for the study of molecular evolution as they provide extreme examples of adaptation to environment. Serpentine outcrops are derived from ultramafic rock and have extremely low levels of essential plant nutrients (e.g. N, P, K, Ca), as well as toxic levels of heavy metals (e.g. Ni, Cr, Co), and very poor moisture availability. These outcrops provide habitat to the endemic plant species, Caulanthus amplexicaulis var. barbarae (J. Howell) Munz (“Cab”). Its sister species, C. amplexicaulis var. amplexicaulis S. Watson (Caa), is found predominately on granite soils and is intolerant to serpentine soils. Comprehensive reference transcriptomes of both Caa and Cab were assembled and annotated for use in protein coding gene comparisons. Reciprocal best Blast hit (RBH) orthologs between Caa and Cab reveal high genome-wide dN/dS ratios between the two taxa. We show that elevated dN/dS results from the composite effects of genetic drift, positive selection, and the relaxation of negative selection. Also, paralogs within each taxon revealed signatures of two periods of elevated gene duplication. In addition, distribution of the synonymous substitution rate, dS, is strongly bimodal indicating two distinct divergence events between the taxa, and suggesting that introgression may have contributed to serpentine adaptation. Further, both common garden and reciprocal transplant experiments on natural granite and serpentine soils were performed using Caa, Cab, and a F1 hybrid. RNA-seq analyses were implemented to calculate global expression patterns and identify differentially regulated genes that may play a role in serpentine adaptation. Results from these analyses depict the complex evolutionary history of the molecular basis of the adaptation to serpentine soil.

1 - Texas A & M University, Department of Biology, 3258 Tamus, College Station, TX, 77843, USA
2 - Department Of Biology, Texas A&M University, TAMUS 3258, College Station, TX, 77843, USA, 979-845-2518

Keywords:
adaptation
Caulanthus
Streptanthus
Brassicaceae
serpentine
endemic
Transcriptome
RNA-Seq.

Presentation Type: Oral Paper
Session: 4, Classical Genetics & Molecular Ecology
Location: Fort Worth Ballroom 8/Omni Hotel
Date: Monday, June 26th, 2017
Time: 9:15 AM
Number: 4005
Abstract ID:484
Candidate for Awards:None