Synergetic Innovation Center of Henan Grain Crops and National Key Laboratory of Wheat and Maize Crop Science, Henan Agricultural University, Zhengzhou, 450046, Henan, China.
Agronomy Department, Faculty of Agriculture, Assiut University, Assiut, Egypt.
BMC Plant Biol. 2021 Oct 6;21(1):453. doi: 10.1186/s12870-021-03231-y.
Appropriate flowering time is very important to the success of modern agriculture. Maize (Zea mays L.) is a major cereal crop, originated in tropical areas, with photoperiod sensitivity. Which is an important obstacle to the utilization of tropical/subtropical germplasm resources in temperate regions. However, the study on the regulation mechanism of photoperiod sensitivity of maize is still in the early stage. Although it has been previously reported that ZmCCT is involved in the photoperiod response and delays maize flowering time under long-day conditions, the underlying mechanism remains unclear.
Here, we showed that ZmCCT overexpression delays flowering time and confers maize drought tolerance under LD conditions. Implementing the Gal4-LexA/UAS system identified that ZmCCT has a transcriptional inhibitory activity, while the yeast system showed that ZmCCT has a transcriptional activation activity. DAP-Seq analysis and EMSA indicated that ZmCCT mainly binds to promoters containing the novel motifs CAAAAATC and AAATGGTC. DAP-Seq and RNA-Seq analysis showed that ZmCCT could directly repress the expression of ZmPRR5 and ZmCOL9, and promote the expression of ZmRVE6 to delay flowering under long-day conditions. Moreover, we also demonstrated that ZmCCT directly binds to the promoters of ZmHY5, ZmMPK3, ZmVOZ1 and ZmARR16 and promotes the expression of ZmHY5 and ZmMPK3, but represses ZmVOZ1 and ZmARR16 to enhance stress resistance. Additionally, ZmCCT regulates a set of genes associated with plant development.
ZmCCT has dual functions in regulating maize flowering time and stress response under LD conditions. ZmCCT negatively regulates flowering time and enhances maize drought tolerance under LD conditions. ZmCCT represses most flowering time genes to delay flowering while promotes most stress response genes to enhance stress tolerance. Our data contribute to a comprehensive understanding of the regulatory mechanism of ZmCCT in controlling maize flowering time and stress response.
合适的开花时间对现代农业的成功非常重要。玉米（Zea mays L.）是一种主要的谷类作物，起源于热带地区，对光周期敏感。这是利用温带地区热带/亚热带种质资源的一个重要障碍。然而，关于玉米光周期敏感性的调节机制的研究仍处于早期阶段。尽管先前已经报道 ZmCCT 参与光周期反应并在长日照条件下延迟玉米开花时间，但潜在的机制仍不清楚。
在这里，我们表明 ZmCCT 的过表达会延迟开花时间，并在 LD 条件下赋予玉米耐旱性。实施 Gal4-LexA/UAS 系统鉴定出 ZmCCT 具有转录抑制活性，而酵母系统显示 ZmCCT 具有转录激活活性。DAP-Seq 分析和 EMSA 表明 ZmCCT 主要结合含有新型基序 CAAAAATC 和 AAATGGTC 的启动子。DAP-Seq 和 RNA-Seq 分析表明，ZmCCT 可以直接抑制 ZmPRR5 和 ZmCOL9 的表达，并促进 ZmRVE6 的表达，以在长日照条件下延迟开花。此外，我们还证明 ZmCCT 直接结合 ZmHY5、ZmMPK3、ZmVOZ1 和 ZmARR16 的启动子，并促进 ZmHY5 和 ZmMPK3 的表达，但抑制 ZmVOZ1 和 ZmARR16 以增强抗逆性。此外，ZmCCT 调节与植物发育相关的一组基因。
ZmCCT 在 LD 条件下具有调节玉米开花时间和应激反应的双重功能。ZmCCT 负调控开花时间，增强 LD 条件下玉米的耐旱性。ZmCCT 抑制大多数开花时间基因以延迟开花，同时促进大多数应激反应基因以增强应激耐受性。我们的数据有助于全面了解 ZmCCT 调节玉米开花时间和应激反应的调控机制。
