Exodermis Differentiation and Function

美国各地的气候越来越难以预测，气温不断上升，水资源供应的极端变化（如干旱和洪水）持续时间更长。这些事件改变了可耕地的可用性，降低了作物产量。植物根部的细胞负责将水分和矿物质营养物质输送到植物的其他部分，它们的细胞是对水分可用性变化的第一个反应者。其中一种细胞类型是外表皮，它在细胞壁上产生屏障，帮助植物变得耐旱。然而，人们对控制其发育或对环境反应的基因知之甚少。在这个项目中，经典的发育生物学方法结合单细胞基因组学和CRISPR-Cas9基因编辑将用于绘制产生根外表皮及其屏障的途径，并确定这种屏障如何帮助番茄植物耐受干旱。这项研究的结果可以直接用于生产能够更好地应对水分供应变化的植物，并促进更可持续的农业。这项研究将完全整合到加州大学戴维斯分校本科生和研究生的教育工作中，并将为他们提供尖端的培训和专业知识。这些学生将进一步建立植物为应对恶劣环境而产生的根细胞屏障纲要。这将使科学家能够利用自然解决方案进行未来的植物育种。植物学研究报告，高达93%的植物物种具有外表皮细胞类型，它位于根表皮之下，并产生屏障。在番茄中，外表皮首先形成极化木质素帽，限制细胞间的被动扩散。调节外皮层木质素屏障形成的基因与调节内皮层发育和Casparian条屏障产生的基因不同。该项目的目标是绘制产生外表皮及其屏障的遗传途径，显示屏障如何调节特定矿物离子的运输，并确定屏障如何发挥作用，帮助植物耐受干旱胁迫。现有的外表皮分化基因将在发育遗传学的遗传途径中排序。CRISPR-Cas9基因编辑将用于有针对性的方法，产生富含外表皮的转录因子和信号基因的成对突变，以确定哪些促进木质素屏障的形成。这种方法将直接整合为加州大学戴维斯分校的基于课程的本科生研究机会，并将形成长期本科生研究项目的基础。单细胞转录组测序将用于鉴定通过其干细胞前体的不对称细胞分裂控制外表皮规格的基因。最后，外皮层和内皮层木质素屏障将在遗传上解耦，以便使用电感耦合等离子体质谱法确定这些屏障如何直接促进植物干旱响应和矿物离子运输。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。

The climate across the United States is increasingly unpredictable, with rising temperatures and longer stretches of extreme changes in water availability such as drought and flooding. These events change arable land availability and reduce crop yield. Cells in the plant root are responsible for transporting water and mineral nutrients to the rest of the plant and their cells are the first responders to changes in water availability. One of these cell types is the exodermis, which is known to produce a barrier in its cell wall that is proposed to aid plants in becoming drought tolerant. However, little is known regarding the genes that control its development or response to the environment. In this project, classical developmental biology approaches coupled with single cell genomics and CRISPR-Cas9 gene editing will be used to map the pathways that produce the root exodermis and its barrier, and to determine how this barrier helps tomato plants tolerate drought. The results of this research can be directly used to generate plants better able to respond to changes in water availability and facilitate more sustainable agriculture. The research will be fully integrated into education efforts for undergraduate and graduate students at the University of California, Davis and will provide them with cutting-edge training and expertise. These students will further establish a compendium of root cell barriers that plants produce to counter a harsh environment. These will enable scientists to harness natural solutions for future plant breeding.Botanical studies report that up to 93% of plant species have an exodermis cell type that underlies the root epidermis and which produces a barrier. In tomato, the exodermis first forms a polarized lignin cap that restricts passive diffusion between cells. The genes that regulate formation of the exodermis lignin barrier are distinct from those that regulate endodermis development and production of the Casparian Strip barrier. The goals of this project are to map the genetic pathway that produces the exodermis and its barrier, to show how the barrier regulates the transport of specific mineral ions and to determine how the barrier functions to help a plant tolerate drought stress. Existing exodermis differentiation genes will be ordered in a genetic pathway using developmental genetics. CRISPR-Cas9 gene editing will be used in a targeted approach to generate pair-wise mutations of exodermis-enriched transcription factors and signaling genes to determine which of these promote formation of the lignin barrier. This approach will be directly integrated as a Course-Based Undergraduate Research opportunity at UC Davis and will form the basis of long-term undergraduate research projects. Single cell transcriptome sequencing will be used to identify genes that control exodermis specification via asymmetric cell divisions of its stem cell precursors. Finally, the exodermis and endodermis lignin barriers will be genetically uncoupled in order to determine how each of these directly contribute to plant drought responses and mineral ion transport using inductively coupled plasma mass spectrometry.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.