Role of TCP transcription factors on the regulation of the circadian clock function in plants

农业集约化和生产区的扩大预计将提高作物产量，以满足未来对粮食和能源的需求。为了实现最佳的生长性能，植物强烈依赖于它们与环境适当相互作用的能力。事实上，大多数植物的反应都表现出昼夜节律（每24小时重复一次的振荡），与环境线索（如光照和温度）的每日节律同步。一个计时机制，被称为昼夜节律钟，是至关重要的，以保持节奏的反应，根据振荡的外部线索。值得注意的是，有人建议微调时钟节奏，使作物品种能够适应不同纬度的生长。植物的生物钟功能受多种环境因素的调节，这些因素在自然界中是同时存在的。然而，在大多数研究中，不同线索的作用是孤立的。因此，组合信号如何调节植物生物钟仍然是一个很大程度上未探索的领域，可以提供关键的见解，了解植物的反应是如何在自然环境中进行调节。该项目旨在通过探索在光和温度循环组合下生长的植物中的时钟调节的新机制来填补这一知识空白。特别是，以前未被识别的时钟组件，差异响应这些环境线索的作用将进行调查。此外，该项目将实施一个系统的培训计划，将提供特殊的学生研究机会。最后，鉴于植物物种之间保守的时钟结构，该项目的结果也可以阐明在未来农业环境中改善作物的新方法。在分子水平上，时钟功能依赖于高度整合的转录网络。转录因子（TF）CCA1和LHY是该网络的核心组成部分，CCA1和LHY表达的时间对于设定时钟节奏至关重要。尽管CCA1和LHY的重要作用，但通过光周期以外的环境信号调节其表达的机制仍然难以捉摸。通过开发一种开创性的策略，主要研究人员从TCP家族中鉴定出一种TF，称为CHE，它调节CCA 1启动子活性，并对时钟功能起着重要作用。初步结果表明，其他TCP与CCA 1启动子和CHE蛋白，以及LHY启动子相互作用。此外，当植物生长在组合的光和温度循环中时，一些鉴定的TCP表现出差异表达模式。因此，本项目的总体假设是，植物时钟功能依赖于TCP TF的协调作用来调节CCA1和LHY的表达。这些研究有望揭示植物生物钟调节的新机制，并通过结合光和温度循环，对植物生物钟在自然界中的功能进行前所未有的评估。最后，这项研究将为改进TF筛选方法的能力提供原则证明，该方法不仅可用于了解植物中的转录机制，还可用于了解其他物种的转录机制。该奖项反映了NSF的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Agriculture intensification and expansion of production areas are expected to provide higher crop yields needed to accommodate future demands of food and energy. To achieve optimal growth performance, plants strongly rely on their ability to properly interact with their environment. In fact, most plant responses exhibit circadian rhythms (oscillations repeated every 24 hours) that are in synchrony with daily rhythms in environmental cues, such as light and temperature. A timekeeping mechanism, known as the circadian clock, is critical to maintain the pace of circadian responses according to oscillations in external cues. Notably, fine-tuning the clock pace was suggested to allow adaptation of crop species to grow at different latitudes. The plant clock function is regulated by multiple environmental cues, which in nature are present simultaneously. However, in most studies the role of different cues was investigated in isolation. Thus, how combined signals modulate the plant clock remains a largely unexplored area that could provide critical insights to understanding how plant responses are regulated in a natural setting. This project aims at filling this gap-in-knowledge by exploring novel mechanisms of clock regulation in plants grown under combined light and temperature cycles. In particular, the role of previously unrecognized clock components that differentially respond to these environmental cues will be investigated. Furthermore, this project will implement a systematic training program that will offer exceptional student research opportunities. Finally, given the conserved clock architecture among plant species, results from this project could also illuminate novel approaches to improve crops in future agricultural settings. At the molecular level, the clock function relies on a heavily integrated transcriptional network. The transcription factors (TFs) CCA1 and LHY are core components of this network and the timing of CCA1 and LHY expression is critical to set the clock pace. Despite their important role, the mechanisms that regulate CCA1 and LHY expression by environmental signals other than light cycles have remained elusive. By developing a pioneering strategy, the principal investigator identified a TF from the TCP family, called CHE, that regulates the CCA1 promoter activity and plays an important role for the clock function. Preliminary results indicate that other TCPs interact with the CCA1 promoter and CHE protein, as well as the LHY promoter. Furthermore, some of the identified TCPs exhibit a differential expression pattern when plants are grown in combined light and temperature cycles. Thus, the overall hypothesis of this project is that the plant clock function relies on the coordinated role of TCP TFs to regulate CCA1 and LHY expression. The proposed studies are expected to reveal novel mechanistic insights of the clock regulation in plants and, by including combined light and temperature cycles, to provide an unprecedented assessment of how the plant clock functions in nature. Finally, this research will provide proof of principle for the power of improved TF screening approaches that could be used to understand transcriptional mechanisms not only in plants but also other species.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.