Role of miR156-targeted SQUAMOSA PROMOTER BINDING PROTEIN-LIKE transcription factors in floral transition

开花是植物生命周期中的主要决定之一，是产生种子和果实所必需的，这些种子和果实支持着地球上的生命。了解这一过程的机制非常重要，这样才能找到应对气候变化挑战和不断增长的人口给农业带来的压力的方法。在许多物种中，植物在开花之前会长出一种独特的叶子。这一阶段是生殖发育的初始阶段，在一年生植物中可能相当短，但在长寿命的多年生植物中延长，其中许多具有相当大的生态和经济重要性。该项目将研究一组被称为SPB盒转录因子的蛋白质如何在模式遗传系统拟南芥（Arabidopsis thaliana）中指定生殖发育的初始阶段。模型系统中的发现可以提供关键信息，这些信息可以在未来转化为农作物。除了提供开花机制的新见解外，该项目还将为博士后研究员，研究生和本科生提供培训机会。本项目研究的一些突变体具有可见的表型，可用于研究K-12教室中的遗传学和植物发育。每年夏天，来自南卡罗来纳州的一到两名K-12学校教师将参与这个项目，并指导他们如何将项目中的一些材料应用到他们的课堂上。在植物的生长过程中，茎尖分生组织产生具有不同发育特性的侧生器官（叶和腋芽）——幼叶、成年叶、茎生叶和花。拟南芥幼苗营养期（V1）和成年营养期（V2）的过渡由miR156及其靶基因SQUAMOSA启动子结合蛋白样（SPL）转录因子调控，而茎生叶期（V3）和花期(R)的过渡由花分生组织识别基因LEAFY和APETALA1调控。花期基因调控V2到V3的转化（花诱导），但指定V3器官（茎叶、次生花序）身份的基因在很大程度上仍然未知。SPL2/SPL9/SPL13/SPL15的突变产生莲座状茎叶，表明这些靶向mir156的SPLs通过指定V3器官身份在促进V2向V3转变中发挥关键作用。该项目将使用分子、遗传和生化方法的组合来确定这些SPLs的上游调节因子和下游目标，这些SPLs参与指定V3器官身份。该项目由植物、真菌和微生物发育机制计划和促进竞争研究的既定计划（EPSCoR）共同资助。该奖项反映了美国国家科学基金会的法定使命，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。

Flowering is one of the major decisions in a plant’s life cycle and is required for producing the seeds and fruits that support life on earth. It is important to understand the mechanism of this process so that ways can be found to respond to the challenges of climate change and to the pressures on agriculture from an ever-increasing population. In many species, plants make a unique type of leaf before making flowers. This phase is the initial stage of reproductive development, and may be quite short in an annual plant, but is extended in long-lived perennial plants, many of which are of considerable ecological and economic importance. This project will investigate how a group of proteins, known as SPB box transcription factors, specify this initial stage of reproductive development in the model genetic system, Arabidopsis thaliana. Discoveries in model systems can provide key information that can be translated to crop plants in the future. In addition to providing new insights into the mechanism of flowering, this project will provide training opportunities for a postdoctoral researcher, a graduate student, and undergraduate students. Some of the mutants studied in this project have visible phenotypes and could be used to study genetics and plant development in K-12 classrooms. One to two K-12 schoolteachers from South Carolina will be engaged in this project each summer, with guidance on how to apply some materials from the project in their classrooms. As a plant grows, the shoot apical meristem produces lateral organs (leaves and axillary buds) with different developmental identities—juvenile leaves, adult leaves, cauline leaves and flowers. In Arabidopsis, the transition between the juvenile vegetative (V1) and adult vegetative (V2) phase is regulated by miR156 and its targets, SQUAMOSA PROMOTER BINDING PROTEIN-LIKE (SPL) transcription factors, whereas the transition between the cauline leaf (V3) and floral (R) phase is regulated by the floral meristem identity genes, LEAFY and APETALA1. Flowering-time genes regulate the V2 to V3 transition (floral induction), but genes that specify the identity of V3 organs (cauline leaves, secondary inflorescences) are still largely unknown. Mutations in SPL2/SPL9/SPL13/SPL15 produce rosette-like cauline leaves, suggesting that these miR156-targeted SPLs play a key role in promoting the V2 to V3 transition by specifying the V3 organ identity. This project will use a combination of molecular, genetic and biochemical approaches to identify the upstream regulators and downstream targets of these SPLs involved in specifying V3 organ identity. This project is jointly funded by the Plant, Fungal and Microbial Developmental Mechanisms Program and the Established Program to Stimulate Competitive Research (EPSCoR).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.