Mapping the molecular basis of growth form divergence in tropical alpine Arabidopsis thaliana

在高山环境中，温度的陡峭梯度可能发生在很短的地理距离内。这使得海拔高度斜坡成为揭示适应的遗传和生理基础以允许在恶劣环境中生存的有效系统。高海拔环境中丰富了几种特殊的生长形式，包括矮小的灌木和平卧的灌木、垫状植物、草本植物和草本莲座状植物。向矮小和更紧凑的形态转变在不同物种中非常常见，并被认为是由于对寒冷温度抵抗力的需求增加所致。拟南芥是一个强大的生态模型，因为我们可以应用这个系统中发展起来的各种遗传和分子工具和知识来识别进化变化的特定分子和遗传基础。我们收集了1000多份来自埃塞俄比亚8个山脉海拔从2222米到4432米的柳杉种质资源，其中包括其中4个山脉的海拔横断面。我们发现高海拔和低海拔种质在生长形式上存在显著差异，来自最高海拔的种质表现出两种极端表型之一：要么表现为极端矮化，要么表现为平卧生长习性，具有斜行生长。这些表型转变让人想起那些经典的与不同物种之间的高海拔有关的转变。这项建议的主要目标是确定导致生长形态变化的遗传变异，并重建埃塞俄比亚AfoalPinA.thaliana中四个重复克隆的这些遗传变异的进化历史。该项目有以下具体目标：目标1：收集12个具有代表性的正常、矮化和剽窃材料的基因组，鉴定结构变异，并产生埃塞俄比亚的全基因组参考。目标2：利用基因组广泛关联(GWA)和重组群体(F2)识别生长形式变异的遗传位点，并评估基于生殖适合性的适应证据目标3：利用群体遗传分析来调查与这些生长形式转变相关的适应性进化的证据。

In alpine environments steep gradients in temperature can occur over short geographical distances. This makes altitudinal clines effective systems for exposing the genetic and physiological basis for adaptations to allow survival in harsh environments. Several specific growth forms are enriched in high altitude environments, including low-stature and prostrate shrubs, cushion plants, tussock grasses and herbaceous rosette plants. Shifts to low-stature and more compact forms are strikingly common across species and have been hypothesized to result from an increased need for resistance to cold temperatures. Arabidopsis thaliana is a powerful ecological model because we can apply diverse genetic and molecular tools and knowledge developed in this system to identify the specific molecular and genetic bases for evolutionary change. We have collected over 1000 A. thaliana accessions from altitudes ranging from 2222 to 4432 m over eight mountain ranges in Ethiopia, including altitudinal transects across four of these. We find striking variation in growth form between high and lower altitude accessions, with accessions from the highest altitudes exhibiting one of two phenotypic extremes: either extreme dwarfism or a prostrate growth habit with plagiotropic growth. These phenotypic shifts are reminiscent of those classically associated with high altitude across diverse species. The main objective of this proposal is to identify the genetic variants responsible for growth form shifts and reconstruct the evolutionary history of these across four replicate clines in Ethiopian Afroalpine A. thaliana. The project has the following specific aims:Objective 1: To assemble 12 representative genomes of normal, dwarf and plagiotropic accessions, identify structural variants, and produce an Ethiopian pan-genome referenceObjective 2: To identify the genetic loci underlying growth form variation using genome wide association (GWAS) and recombinant populations (F2s) and assess evidence of adaptation based on reproductive fitnessObjective 3: To investigate evidence for adaptive evolution related to these growth form shifts using population genetic Analysis.