Data from: Independent FLC mutations as causes of flowering time variation in Arabidopsis thaliana and Capsella rubella

Capsella rubella is an inbreeding annual forb closely related to Arabidopsis thaliana, a model species widely used for studying natural variation in adaptive traits such as flowering time. Although mutations in dozens of genes can affect flowering of A. thaliana in the laboratory, only a handful of such genes vary in natural populations. Chief among these are FRIGIDA (FRI) and FLOWERING LOCUS C (FLC). Common and rare FRI mutations along with rare FLC mutations explain a large fraction of flowering-time variation in A. thaliana. Here we document flowering time under different conditions in 20 C. rubella accessions from across the species' range. Similar to A. thaliana, vernalization, long photoperiods and elevated ambient temperature generally promote flowering. In this collection of C. rubella accessions, we 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. However, other similarly early C. rubella accessions did not share this mutation. We conclude that the genetic basis of flowering-time variation in C. rubella is complex, despite this very young species having undergone an extreme genetic bottleneck when it split from C. grandiflora a few tens of thousands of years ago.

红荠（Capsella rubella）是一种自交型一年生草本，与广泛用于研究开花时间等适应性性状自然变异的模式物种拟南芥（Arabidopsis thaliana）亲缘关系紧密。尽管实验室环境下数十个基因的突变均可影响拟南芥的开花进程，但在自然种群中仅少数这类基因存在序列变异。其中发挥核心作用的是FRIGIDA（FRI）基因与开花位点C（FLOWERING LOCUS C，FLC）基因。常见与罕见的FRI突变，搭配罕见的FLC突变，可解释拟南芥中绝大多数的开花时间表型变异。本研究针对覆盖红荠物种分布范围的20份种质材料，测定了其在不同环境条件下的开花时间。与拟南芥一致，春化处理、长日照条件与升高的环境温度普遍能够促进红荠开花。在本次收集的红荠种质材料中，未检测到任何明确的功能丧失型FRI等位基因。通过对两种开花习性存在显著差异的菌株开展测序定位分析，我们鉴定出FLC基因上的一处剪接位点突变，该突变极有可能是1408号种质材料早开花的分子诱因。但其余表现为早开花表型的红荠种质材料，均未携带该突变。研究结果表明，尽管红荠作为一个极为年轻的物种，在数万年前由大花荠（Capsella grandiflora）分化而来并经历了极端的遗传瓶颈，但其开花时间变异的遗传基础依然较为复杂。