The Role of Cell Cycle Regulation in Leaf Development

归根结底，世界上所有的粮食供应，以及许多其他关键产品，都依赖于植物从阳光中获取的能量。这种阳光被树叶捕捉到，树叶的形状优化了采光能力，同时最大限度地减少了水分损失。一些植物的叶片也适应于生长在极端环境中，如高胁迫或高盐条件，这表明对环境的生长反应存在基因控制。了解树叶如何通过细胞生长来适应环境，将为面对不断变化的环境具有弹性和可持续的农业提供基础信息。叶片一般通过分裂增加细胞数量，然后通过扩张增加细胞大小来生长。目前尚不清楚这两个分裂和扩张过程是如何控制的，从而形成叶子的最终形状。这项研究探索了在遗传模式植物拟南芥中限制细胞分裂并促进向细胞扩张切换的调控因子家族的功能。然后，这些发现被应用于研究如何控制细胞扩张，以应对盐适应植物细小志贺氏菌叶片中的盐暴露。了解植物如何在极端的盐胁迫条件下生长，将提供有关植物如何响应和适应环境的基本信息。下一代科学家将通过在实验室的经验和开发以课程为基础的植物生物学本科研究项目，接受实践研究方面的培训。暹罗相关(SMR)家族最早是在拉金实验室发现的，是从细胞增殖向内复制过渡的关键调节因子，内复制是细胞周期的一个替代版本，DNA复制在这个版本中继续进行，而不是随后的分裂。SMR1和SMR2这两个家族成员对拟南芥的叶细胞数、细胞大小和总叶大小有明显的影响。我们的中心假设是，SMR通过控制叶片发育过程中内复制的时机和程度，在发育和环境信号中作为叶片生长的关键调节因子。这一假说将通过研究SMR1和SMR2基因在叶片发育过程中的调节和功能作用，以及SMRs在小球藻叶片发育对盐处理的响应中的作用来验证。这项工作将有助于识别控制叶片内复制起始的调控网络，并有助于理解内复制在叶片功能和胁迫适应中的作用，并将为极端植物模型小球藻开发资源。拟议的工作将对来自不同背景的三名研究生和几名本科生的教育起到作用。还计划建立一个以课程为基础的本科生研究体验(CURE)实验室，重点研究基因表达，使用SMR启动子：报告融合转基因品系，将作为拟议研究的一部分。该奖项反映了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。

Ultimately, all of the world’s food supply, as well as many other crucial products, depend on energy harvested from sunlight by plants. This sunlight is captured by leaves that have shapes optimized for light harvesting while minimizing water loss. Leaves of some plants are also adapted to growing in extreme environments such as high stress or high salt conditions, showing that there are genetic controls of growth responses to the environment. Understanding how leaves adapt to the environment through cell growth will provide foundational information for a resilient and sustainable agriculture in the face of changing environments. Leaves generally grow by increasing cell number through division followed by an increase in cell size by expansion. It is not clear how these two processes of division and expansion are controlled to give rise to the final shape of a leaf. This research explores the function of a family of regulators that restrict cell division and promote the switch to cell expansion in the genetic model plant Arabidopsis thaliana. The findings are then applied to study how cell expansion is controlled in response to salt exposure in leaves of the salt-adapted plant Schrenkiella parvula. Understanding how plants can grow in extreme salt-stressed conditions will provide basic information about how plants respond and adapt to the environment. The next generation of scientists will be trained in hands-on research through experience in the laboratory and by developing course-based undergraduate research projects in plant biology. The SIAMESE-RELATED (SMR) family of cyclin-dependent kinase inhibitors, first discovered in the Larkin lab, are key regulators of the transition from cell proliferation to endoreplication, an alternate version of the cell cycle in which DNA replication continues without subsequent division. Two family members, SMR1 and SMR2, have distinct effects on leaf cell number, cell size and overall leaf size in Arabidopsis thaliana. Our central hypothesis is that SMRs serve as key regulators of leaf growth for both developmental and environmental cues by controlling the timing and extent of endoreplication during leaf development. This hypothesis will be tested by examining the regulation and functional roles of the SMR1 and SMR2 genes during leaf development, and by examining the role of SMRs in Schrenkiella parvula leaf development in response to salt treatment. This work will contribute to the identification of regulatory networks controlling the onset of endoreplication in leaves, and to understanding the role of endoreplication in leaf function and stress adaptation, and will develop resources for the extremophyte model S. parvula. The proposed work will play a role in the education of three graduate students and several undergraduates from a wide diversity of backgrounds. A course-based undergraduate research experience (CURE) lab focusing on gene expression is also planned, using SMR promoter:reporter fusion transgenic lines that will be produced as part of the proposed research.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.