Shi Yong, Zhao Xiyong, Guo Sha, Dong Shifeng, Wen Yanpeng, Han Zanping, Jin Weihuan, Chen Yanhui
College of Agronomy/National Key Laboratory of Wheat and Maize Crop Science, Henan Agricultural University, Zhengzhou, China.
Crop Research Institute, Anhui Academy of Agricultural Sciences, Hefei, China.
Front Plant Sci. 2020 Feb 20;11:78. doi: 10.3389/fpls.2020.00078. eCollection 2020.
Maize () is a major cereal crop that originated at low latitudes, and thus photoperiod sensitivity is an important barrier to the use of tropical/subtropical germplasm in temperate regions. However, studies of the mechanisms underlying circadian regulation in maize are at an early stage. In this study we cloned on chromosome 10 of maize by map-based cloning. The gene is homologous to the Myb transcription factor genes / in ; the deduced Myb domain of ZmCCA1a showed high similarity with that of AtCCA1/AtLHY and ZmCCA1b. Transiently or constitutively expressed ZmCCA1a-YFPs were localized to nuclei of mesophyll protoplasts, agroinfiltrated tobacco leaves, and leaf and root cells of transgenic seedlings of . Unlike AtCCA1/AtLHY, ZmCCA1a did not form homodimers nor interact with ZmCCA1b. Transcripts of showed circadian rhythm with peak expression around sunrise in maize inbred lines CML288 (photoperiod sensitive) and Huangzao 4 (HZ4; photoperiod insensitive). Under short days, transcription of in CML288 and HZ4 was repressed compared with that under long days, whereas the effect of photoperiod on expression was moderate in HZ4. In overexpressing () lines, the circadian rhythm was disrupted under constant light and flowering was delayed under long days, but the hypocotyl length was not affected. In addition, expression of endogenous and the downstream genes , , and was repressed in seedlings. The present results suggest that the function of is similar, at least in part, to that of and , implying that is likely to be an important component of the circadian clock pathway in maize.
玉米（）是一种起源于低纬度地区的主要谷类作物，因此光周期敏感性是温带地区利用热带/亚热带种质的一个重要障碍。然而，玉米中昼夜节律调控潜在机制的研究尚处于早期阶段。在本研究中，我们通过图位克隆在玉米第10号染色体上克隆了。该基因与中的Myb转录因子基因/同源；推导的ZmCCA1a的Myb结构域与AtCCA1/AtLHY和ZmCCA1b的Myb结构域具有高度相似性。瞬时或组成型表达的ZmCCA1a-YFPs定位于玉米叶肉原生质体、农杆菌浸润的烟草叶片以及转基因幼苗的叶和根细胞的细胞核中。与AtCCA1/AtLHY不同，ZmCCA1a不形成同二聚体，也不与ZmCCA1b相互作用。在玉米自交系CML288（光周期敏感）和黄早4（HZ4；光周期不敏感）中，的转录本呈现昼夜节律，在日出前后表达量达到峰值。在短日照条件下，与长日照相比，CML288和HZ4中的转录受到抑制，而光周期对HZ4中表达的影响适中。在过表达（）的株系中，在持续光照下昼夜节律被破坏，在长日照下开花延迟，但下胚轴长度不受影响。此外，在幼苗中，内源性和下游基因、、和的表达受到抑制。目前的结果表明，的功能至少部分类似于和，这意味着可能是玉米昼夜节律途径的一个重要组成部分。
