背景回顾：Maize (Zea mays) originated in southern Mexico and has spread over a wide latitudinal range. Maize expansion from tropical to temperate regions has necessitated a reduction of its photoperiod sensitivity.  

主要发现：In this study, we cloned a quantitative trait locus (QTL) regulating flowering time in maize and show that the maize ortholog of Arabidopsis thaliana EARLY FLOWERING3, ZmELF3.1, is the causal locus. 

结果1-ELF3.1及其功能：We demonstrate that ZmELF3.1 and ZmELF3.2 proteins can physically interact with ZmELF4.1/4.2 and ZmLUX1/2, to form evening complex(es) (EC) in the maize circadian clock. Loss-of-function mutants for ZmELF3.1/3.2 and ZmLUX1/2 exhibited delayed flowering under long-day and short-day conditions. 

结果2-EC促进开花的机制：We show that EC directly represses the expression of several flowering suppressor genes, such as the CONSTANS, CONSTANS-LIKE, TOC1 (CCT) genes ZmCCT9 and ZmCCT10, ZmCONSTANS-LIKE 3, and the PSEUDORESPONSE REGULATOR (PRR) genes ZmPRR37a and ZmPRR73, thus alleviating their inhibition, allowing florigen gene expression and promoting flowering. 

结果3-ELF3.1启动子：Further, we identify two closely linked retrotransposons located in the ZmELF3.1 promoter that regulate the expression levels of ZmELF3.1 and may have been positively selected during post-domestication spread of maize from tropical to temperate regions during the pre-Columbian era. 

结论：These findings provide insights into circadian clock-mediated regulation of photoperiodic flowering in maize and new targets of genetic improvement for breeding.

 摘 要 

玉米起源于墨西哥南部地区，目前在全球的种植横跨很宽的纬度范围。玉米从热带地区向温带地区的扩张伴随着对光周期敏感性的降低。本文中，作者克隆到了一个玉米中调控开花时间的数量性状位点，发现拟南芥EFL3在玉米中的同源基因ZmELF3.1是该QTL的关键基因。作者发现ZmELF3.1和ZmELF3.2蛋白能够与ZmELF4.1/4.2和ZmLUX1/2发生物理互作，从而形成一个玉米生物钟晚间复合物EC。ZmELF3.1/3.2和ZmLUX1/2基因的功能缺失会导致其无论是在长日照，还是在短日照条件下，都会延迟开花。作者发现EC直接抑制一些开花抑制基因的表达，比如CCT基因ZmCCT9、ZmCCT10和ZmCOL3以及PRR基因ZmPRR37a和ZmPRR73，进而减轻这些基因对于开花的抑制，最终使得一个成花基因得以表达并促进开花。此外，作者在ZmELF3.1基因启动子上鉴定到了两个个紧密连锁的转座子，可以调控ZmELF3.1基因的表达，可能在前哥伦布时代玉米从热带向温带扩张并在地域驯化后受到了正选择。本文的研究结果揭示了玉米中一个生物钟介导的光周期调控机制，并为作物的遗传改良提供了一个新的候选靶点。

** 王海洋 **