Evolutionary genomics and natural variation of Arabidopsis relatives
Ya-Long Guo*

State Key Laboratory of Systematic and Evolutionary Botany, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China
*Corresponding Author：Tel: (+8610) 6283 6298; E-mail: yalong.guo@ibcas.ac.cn

Abstract
Arabidopsis relatives is a good model system for the study of genomics and natural variation. The S locus is a single polymorphic locus, which is responsible for self-incompatibility (SI) in the Brassicaceae family. Despite its importance, our knowledge of S-locus evolution is largely restricted to the causal genes encoding the SRK receptor and SCR ligand of the SI system. We present high-quality sequences of the genomic region of six S-locus haplotypes from Arabidopsis thaliana, Arabidopsis lyrata, and Capsella rubella. We found that duplication, gene conversion, and positive selection have been important factors in the evolution of these two genes, and appear to contribute to the generation of new recognition specificities. C. rubella is an inbreeding annual forb closely related to Arabidopsis thaliana. Common and rare FRI mutations along with rare FLC mutations explain a large fraction of flowering time variation in A. thaliana. We document flowering time under different conditions in 20 C. rubella accessions from across the species’ range, and did not find any obvious loss-of-function FRI alleles. Using mapping-by-sequencing with two strains that have contrasting flowering behaviors, we identified a splice-site mutation in FLC as the likely cause of early flowering in accession 1408.

Key Words: Arabidopsis relatives; Evolutionary genomics; Natural variation; S locus