Extremophyte Crucifer Species: A Comparative Framework to Study Genome Variations That Lead to Niche Adaptations

Schrenkiella parvula and Eutrema salsugineum (formerly Thellungiella parvula and T. salsuginea) are wild-relatives of Brassica crops and adapted to extremely saline habitats.  Native to the shores of Lake Tuz ("salt" in Turkish), S.parvula can survive the presence of toxic levels of multiple ions, including Na⁺, as well as Li⁺, K⁺, Mg²⁺, and borates. In comparison with the genome of Arabidopsis, variations in genome structures and transcriptome expression profiles of ion transporter genes have been identified. Among these genome structural variations (SVs), for exmaple, a large insertion, around 15 kb, is found at the upstream of SpBOR5, a putative boric acid transporter.  Basal level expression of SpBOR5 is >500 fold higher than that of AtBOR5, further highlighting the possibility of SpBOR5 being determinant for borate tolerance in S.parvula, and the significance of the large insertion than might lead to significant this significant expression difference.  We present the on-going study identifying and functionally characterizing structural variations within the crucifer lineage, based on a comparative framework including genomes of extremophytes, crop, and model species.