From its tropical origin in southwestern Mexico, maize spread over a wide latitudinal cline in the Americas. This feat defies the rule that crops are inhibited from spreading easily across latitudes. How the widespread latitudinal adaptation of maize was accomplished is largely unknown. Through positional cloning and association mapping, we resolved a flowering-time quantitative trait locus to a Harbinger-like transposable element positioned 57 kb upstream of a CCT transcription factor (ZmCCT9). The Harbinger-like element acts in cis to repress ZmCCT9 expression to promote flowering under long days. Knockout of ZmCCT9 by CRISPR/Cas9 causes early flowering under long days. ZmCCT9 is diurnally regulated and negatively regulates the expression of the florigen ZCN8, thereby resulting in late flowering under long days. Population genetics analyses revealed that the Harbinger-like transposon insertion at ZmCCT9 and the CACTA-like transposon insertion at another CCT paralog, ZmCCT10, arose sequentially following domestication and were targeted by selection for maize adaptation to higher latitudes. Our findings help explain how the dynamic maize genome with abundant transposon activity enabled maize to adapt over 90° of latitude during the pre-Columbian era.

中文翻译：

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ZmCCT9增强了玉米对更高纬度的适应性

玉米起源于墨西哥西南部的热带地区，遍布美洲的宽阔纬线。这一壮举违反了禁止农作物在整个纬度范围内轻易蔓延的规定。玉米广泛的横向适应是如何完成的，在很大程度上尚不清楚。通过位置克隆和关联映射，我们将开花时间的定量性状基因座解析为位于CCT转录因子（ZmCCT9）上游57 kb的Harbinger样转座因子。在长日照下，类似Harbinger样元件可顺式抑制ZmCCT9表达以促进开花。CRISPR / Cas9敲除ZmCCT9导致长时间开花。ZmCCT9它是昼夜调节的，而负离子调节的是荧光素ZCN8的表达，从而导致长时间开花较晚。群体遗传学分析显示，驯化后依次出现了在ZmCCT9处类似Harbinger的转座子和在另一个CCT旁系同源物ZmCCT10上的类似CACTA的转座子，它们的选择是针对玉米适应高纬度的选择。我们的发现有助于解释具有丰富转座子活性的动态玉米基因组如何使玉米在哥伦布时代之前的时代适应90度以上的纬度。