Natural variation in trichome pattern (amount and distribution) is prominent among populations of many angiosperms. However, the degree of parallelism in the genetic mechanisms underlying this diversity and its environmental drivers in different species remain unclear. To address these questions, we analyzed the genomic and environmental bases of leaf trichome pattern diversity in Cardamine hirsuta, a relative of Arabidopsis (Arabidopsis thaliana). We characterized 123 wild accessions for their genomic diversity, leaf trichome patterns at different temperatures, and environmental adjustments. Nucleotide diversities and biogeographical distribution models identified two major genetic lineages with distinct demographic and adaptive histories. Additionally, C. hirsuta showed substantial variation in trichome pattern and plasticity to temperature. Trichome amount in C. hirsuta correlated positively with spring precipitation but negatively with temperature, which is opposite to climatic patterns in A. thaliana. Contrastingly, genetic analysis of C. hirsuta glabrous accessions indicated that, like for A. thaliana, glabrousness is caused by null mutations in ChGLABRA1 (ChGL1). Phenotypic genome-wide association studies (GWAS) further identified a ChGL1 haplogroup associated with low trichome density and ChGL1 expression. Therefore, a ChGL1 series of null and partial loss-of-function alleles accounts for the parallel evolution of leaf trichome pattern in C. hirsuta and A. thaliana. Finally, GWAS also detected other candidate genes (e.g. ChETC3, ChCLE17) that might affect trichome pattern. Accordingly, the evolution of this trait in C. hirsuta and A. thaliana shows partially conserved genetic mechanisms but is likely involved in adaptation to different environments.

中文翻译：

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碎米荠的毛状体模式多样性与拟南芥具有相同的遗传机制，但环境驱动因素不同

在许多被子植物种群中，毛状体模式（数量和分布）的自然变异是显着的。然而，这种多样性背后的遗传机制及其在不同物种中的环境驱动因素的平行程度仍不清楚。为了解决这些问题，我们分析了拟南芥（Arabidopsis thaliana）的近缘种碎米荠叶毛状体模式多样性的基因组和环境基础。我们对 123 个野生种质的基因组多样性、不同温度下的叶毛模式和环境调整进行了表征。核苷酸多样性和生物地理分布模型确定了两个具有不同人口统计和适应历史的主要遗传谱系。此外，C. hirsuta 在毛状体模式和可塑性方面表现出显着的温度变化。粗毛拟南芥的毛状体数量与春季降水量呈正相关，但与温度呈负相关，这与拟南芥的气候模式相反。相比之下，毛毛茛无毛种质的遗传分析表明，与拟南芥一样，无毛是由 ChGLABRA1 (ChGL1) 的无效突变引起的。表型全基因组关联研究 (GWAS) 进一步鉴定了与低毛状体密度和 ChGL1 表达相关的 ChGL1 单倍群。因此，ChGL1 系列无效和部分功能丧失的等位基因解释了毛草和拟南芥叶毛状体模式的平行进化。最后，GWAS还检测到其他可能影响毛状体模式的候选基因（例如ChETC3、ChCLE17）。因此，毛毛拟南芥和拟南芥这一性状的进化显示出部分保守的遗传机制，但可能与对不同环境的适应有关。