ZmELF3调控玉米开花期和生态适应性的功能研究

Maize is one of the largest crops in China and worldwide. Flowing time is a critical determinant of maize yield and regional adaptation. Previous studies have documented a key role of Early Flowering 3 (ELF3) in regulating flowering and regional adaptation in many plant species, including crops. The maize genome contains two homologues of ELF3 (ZmELF3-1 and ZmELF3-2), however, their roles in regulating flowering time have not been reported yet. Our preliminary evidences indicated that the zmelf3s double mutant exhibited a significant delay in flowering time (over a month in long-day conditions), ZmELF3s physically interact with ZmLUXs (a MYB-type transcription factor involved in regulating the circadian clock), and that ZmELF3-1 shows selection signatures in maize breeding history. In this project, we will: 1) Determine the biological function of ZmELF3s in flowering time control by phenotyping its CRISPR/Cas9 and overexpression transgenic lines; 2) Investigate the genetic regulatory network that ZmELF3s regulate flowering via interacting with ZmLUXs, and influencing the expression of ZmCCTs; 3) Identify the superior alleles of ZmELF3s through association studies and haplotype analyses. The predicted results will deepen our understanding of the genetic control of maize flowing time and help to guide breeding of maize cultivars better adapted to specific planting region.

玉米是目前我国乃至全球种植范围最广、需求量最大的谷类作物之一。适宜的开花期是决定玉米生态适应性和保证玉米生产的关键。已知ELF3在调控多种植物的开花期和生态适应性方面起重要作用，而玉米中两个ELF3同源基因(ZmELF3-1和ZmELF3-2)的功能研究还未有报道。我们前期的研究发现zmelf3s双突变体明显晚花，ZmELF3s蛋白可与生物钟关键因子ZmLUXs直接互作，且ZmELF3-1在玉米育种过程中受到选择。本项目中，我们将通过对ZmELF3s的CRISPR和过表达转基因株系进行表型分析来解析其生物学功能；利用多种生物学和遗传学手段验证“ZmELF3通过与ZmLUXs互作调控ZmCCT9/10的表达进而调控玉米开花”的遗传网络；并通过候选基因关联分析和选择分析鉴定其优异单倍型。预期研究结果将加深我们对玉米开花遗传调控基础的理解，并可为玉米花期和地域适应性育种提供理论支撑和材料基础。

玉米是目前我国乃至全球种植范围最广、需求量最大的谷类作物之一。适宜的开花期是决定玉米生态适应性和保证玉米生产的关键。然而，一直以来玉米关键开花调控基因的挖掘及光周期适应性的遗传基础研究还十分滞后。本项目中 1）我们克隆了重要玉米花期QTL的候选基因ZmELF3.1，证明其在玉米开花调控方面发挥着关键作用，且ZmELF3.1和ZmELF3.2基因之间存在着部分功能冗余。2）建立了ZmELF3.1/ZmELF3.2通过介导ZmELF4.1/ZmELF4.2和ZmLUX1/ZmLUX2形成EC复合体来抑制下游开花抑制基因ZmCCT9、ZmCOL3、ZmPRR37a和ZmPRR73的表达，从而解除对下游成花素基因ZCN8、ZCN7、ZCN12的抑制，最终促进玉米开花的遗传通路。3）通过群体遗传学手段挖掘了位于ZmELF3.1启动子区的功能性自然变异，证明了ZmELF3.1启动子区两个紧密连锁的逆转座子的插入可促进玉米早花，并在玉米由热带向温带的适应过程中受到正向选择、对玉米种植区域的扩张和拓展具有重要作用。研究结果将加深我们对玉米开花遗传调控基础的理解，并为玉米花期和地域适应性育种提供重要的理论指导和基因资源。

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