Regulation of stem cell patterning and activity in Citrus

非技术段落：植物通过干细胞群体的作用而生长，干细胞群体在中轴周围以高度调节的模式产生枝条、叶子和花朵。这种模式被称为叶序。虽然大多数植物都表现出螺旋状的叶序，但柑橘种在叶序上表现出一种不寻常的变异；许多柑橘种不是以螺旋模式出现的单枝原基，而是产生两个相邻的、具有不同发育潜力的原基。一个原基发育成典型的分枝，而另一个原基分化为刺。先前的研究表明，树枝和棘原基以不同的方式调节干细胞的活动。这个项目的目标是了解这种不同寻常的叶系模式是如何在柑橘中形成的，并研究干细胞活动的差异在枝原基和棘原基中是如何调节的相关问题。叶、枝和花的排列是作物产量的关键组成部分。因此，在柑橘上开展这项工作将通过了解控制这种重要经济作物的生长和产量的机制来支持生物经济。此外，这项工作有可能为这种水果商品的工程提供新的工具，以及更广泛地提供有关植物生长和发育的机械方面的信息。该项目还将有助于本科生、研究生和博士后研究人员的职业发展，并为当地纽黑文地区社区和服务不足的高中生提供一种延伸的手段。技术段落：植物激素生长素是以定向方式运输的，原基起始部位的生长素活动被认为定义了叶序和器官发育的模式。了解生长素信号如何与其他信号成分相互作用，以定义两种不同的发育结果，刺和分支原基，将有助于洞察干细胞的模式过程以及它们如何转化为有机体形式。这项拟议的工作包括评估柑橘中生长素的分布和活性，以及扰乱柑橘中生长素作用的多种实验方法。这些实验将得到对刺与分支转录组的全基因组评估，以及对刺IDENTITY1(TI1)全基因组结合位点的评估，TI1编码一种CyC/BRC1类TCP转录因子，通过与干细胞调节因子WUS的启动子结合并下调其表达来确定刺的身份。总的来说，所提出的实验将有助于确定生长素信号如何影响产生刺与枝原基的决定，以及这些信号如何与调控刺与枝身份的基因调控网络的组成部分相互作用。定义调节生长素信号和干细胞活动之间相互作用的机制应该有助于揭示新的调控目标，这些目标可以通过基因操作来改变植物结构和影响作物产量。这一奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Non-technical paragraph:Plants grow by the action of stem cell populations, which give rise to branches, leaves and flowers in a highly regulated pattern around the axis. This pattern is called phyllotaxy. While most plant species show spiral phyllotaxy, citrus species present an unusual variation on phyllotaxy; instead of single branch primordia arising in a spiral pattern, many citrus species instead produce two adjacent primordia with differing developmental potentials. One primordium develops into a typical branch, while the other primordium differentiates as a thorn. Previous work has shown that the branch and the thorn primordia regulate stem cell activity in different ways. The goals of this project are to understand how this unusual phyllotactic pattern is formed in citrus, and to examine the related issue of how differences in stem cell activity are regulated in branch versus thorn primordia. The arrangement of leaves, branches, and flowers is a key component of crop yield. As such, carrying out this work in citrus will support the bioeconomy through knowledge of the mechanisms controlling growth and yield of this economically important crop. In addition, this work has the potential to provide new tools for the engineering of this fruit commodity, as well as providing information on mechanistic aspects of plant growth and development more broadly. This project will also contribute to the career development of undergraduate, graduate student and postdoctoral researchers, as well as provide a means for outreach to the local New Haven area community and underserved high school students.Technical paragraph: The plant hormone auxin is transported in a directional manner and auxin activity at the sites of primordia initiation is thought to define both the pattern of phyllotaxy and organ outgrowth. Understanding how auxin signaling interacts with other signaling components to define two different developmental outcomes, the thorn versus the branch primordium, will provide insight into stem cell patterning processes and how they translate into organismal forms. The proposed work includes assessing auxin distribution and activity in Citrus, as well as multiple experimental approaches to perturb auxin action in Citrus. These experiments will be complemented by genome wide evaluation of the thorn versus branch transcriptome, as well as an assessment of the genome-wide binding sites of THORN IDENTITY1 (TI1), encoding a CYC/BRC1 class TCP transcription factor, that functions to specify thorn identity through binding to the promoter of the stem cell regulator WUS and downregulating its expression. Collectively, the proposed experiments will help to define how auxin signaling influences the decision to produce a thorn versus a branch primordium, and how such signals interface with the components of the gene regulatory network regulating thorn versus branch identity. Defining the mechanisms regulating the interplay between auxin signaling and stem cell activity should help to reveal new regulatory targets that could be genetically manipulated to alter plant architecture and influence crop productivity.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.