Solidago canadensis , originating from the temperate region of North America, has expanded southward to subtropical regions through polyploidization. Here we investigated whether freezing tolerance of S. canadensis was weakened during expansion. Measurement of the temperature causing 50% ruptured cells (LT₅₀) in 35 S. canadensis populations revealed ploidy‐related differentiation in freezing tolerance. Freezing tolerance was found to decrease with increasing ploidy. The polyploid populations of S. canadensis had lower ScICE1 gene expression levels but more ScICE1 gene copies than the diploids. Furthermore, more DNA methylation sites in the ScICE1 gene promoter were detected in the polyploids than in the diploids. The results suggest that promoter methylation represses the expression of multi‐copy ScICE1 genes, leading to weaker freezing tolerance in polyploid S. canadensis compared to the diploids. The study provides empirical evidence that DNA methylation regulates expression of the gene copies and supports polyploidization‐driven adaptation to new environments.

中文翻译：

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多倍体化驱动加拿大一枝黄花耐寒性的分化。

加拿大一枝黄花起源于北美的温带地区，通过多倍体化已向南扩展到亚热带地区。在这里我们调查了加拿大S. canadensis的抗冻能力在扩增过程中是否减弱。在35个加拿大加拿大链球菌种群中，引起50％细胞破裂的温度（LT ₅₀）的测量结果显示了倍数相关的耐寒性差异。发现抗冻性随倍性的增加而降低。加拿大S.canadensis的多倍体种群比二倍体具有较低的ScICE1基因表达水平，但具有更多的ScICE1基因拷贝。此外，ScICE1中更多的DNA甲基化位点在多倍体中检测到的基因启动子比在二倍体中检测到。结果表明，与二倍体相比，启动子甲基化抑制了多拷贝ScICE1基因的表达，从而导致多倍体加拿大念珠菌的冷冻耐受性较弱。这项研究提供了经验证据，证明DNA甲基化调节基因拷贝的表达并支持多倍体化驱动的适应新环境。