野生種紅豆染色體易位的演化

Abstract

染色體倒位可能藉由抑制局部適應等位基因之間的重組，以促進地區性適應。然而，少有研究探討染色體易位在地區性適應中的重組抑制機制。生長在日本的紅豆包含具有染色體易位的野生種紅豆、不具有染色體易位的野生種紅豆、雜草型紅豆和栽培種紅豆，其族群遺傳歷史仍有待釐清。在本研究中，我們發現雜草型紅豆起源於栽培種族群與南邊野生種族群間的雜交。在北邊野生種族群擴張至日本北部後，染色體易位才出現並向北擴張。此外，重組抑制保留從著絲粒到斷點的高度連鎖之適應性等位基因，有助於帶有染色體易位的野生種紅豆適應日本北部的環境。總結來說，我們的研究結果顯示，具有染色體易位的野生種紅豆能夠部分限制野生種紅豆和栽培種紅豆之間的基因交流，從而防止雜草型紅豆的產生。另外，我們提出的模型假設，當適應性等位基因位於染色體易位的斷點周圍，受到重組抑制和高度連鎖的等位基因將被保留於其中。而我們的結果亦支持此一模型解釋。

Chromosomal inversions may contribute to local adaptation by suppressing recombination between locally adapted alleles. However, few studies focus on mechanisms of recombination suppression of chromosomal translocations in local adaptation. Population genetic history of Japanese adzuki beans, including normal wild, translocated wild, weedy, and landrace forms, remains unclear. Here, we reveal that weedy adzuki beans (JP_WD) originated through the hybridization between the landrace genetic group (JP_LR) and the wild genetic group in South Japan (JP_WLsouth). After the wild genetic group in North Japan (JP_WLnorth) had established across northern Japan, the translocations might have originated and spread. Recombination suppression preserved highly linked adapted alleles from centromeres to breakpoints, facilitating the wild adzuki beans with the translocations adapt to North Japan. In summary, our findings show that chromosomal translocations partially prevent the wild-cultigen gene flow, thereby preventing creation of weedy adzuki beans. Our proposed models assume that when suppressed recombination occurs among locally adapted alleles near translocation breakpoints, the highly linked adapted alleles would be retained. The models are supported by our results.