RESEARCH-PGR: Dissecting the Genetic Networks Underlying Kranz Anatomy in C4 Grasses

Pi：Thomas Brutnell[唐纳德·丹福斯植物科学中心(DDPSC)]Copis：Elizabeth Kellogg和Todd Mockler(DDPSC)，Kimberly Gallagher(宾夕法尼亚大学)，Chris Myers(康奈尔大学)和Joyce Van Eck(博伊斯·汤普森植物科学研究所)高级人员：Robert Turjo，齐Sun和Klaas van Wijk(康奈尔大学)产量下降，人口增长和气候变化汇聚在一起，为农业创造了一场完美的风暴。迫在眉睫的粮食安全威胁要求农业进行革命性创新，以推动第二次绿色革命。玉米是美国最重要的经济作物，为全球经济提供食物、饲料和生物能源。它也是地球上光合作用生产率最高的植物之一。这种生产力是由与C4光合作用相关的生化和解剖适应驱动的。一个被提出的重大挑战是将C4特性引入C3作物，如水稻和许多温带牧草。通过发现根内胚层细胞命运模块被增选来驱动叶片特异的细胞分化程序，在理解C4光合作用的发展方面实现了重大的概念性突破。重要的是，这个模型的预测表明，有限数量的基因变化可能会导致叶细胞命运的重大重新编程。这个项目将验证这一预测，并扩大我们对基因调控网络的理解，这些基因调控网络驱动与C4光合作用相关的生化和解剖创新。这些研究结果不仅将为将C4性状导入C3作物提供候选基因，还将为玉米、甘蔗、高粱等现有C4作物的改良提供新的靶点。在培训和外联方面，该项目将继续扩大DDPSC的MutantMillets外联方案。MutantMillets提供植物科学实践活动的教学模块和教学资源，以吸引圣路易斯大都市区的高中生。重要的是，通过该方案开发的所有资源将可通过项目网站和由教育和推广中心在DDPSC建立的教育网络移植到其他学校系统。利用C4光合作用的草包括玉米、高粱、甘蔗和芒属。C4草使用两种不同的细胞类型来创建二氧化碳泵，该泵提高了Rubisco酶附近的二氧化碳水平，有效地消除了浪费的光呼吸。在炎热、干燥的条件下，与水稻和小麦等C3作物相比，C4系统表现出显著的生产力提高。该项目旨在确定控制玉米两种光合作用细胞类型--束鞘(BS)和叶肉(M)--分化的基本遗传和调控网络。这项工作扩展了最近的发现，将SHR/SCR/IDD调控模块与玉米BS和M细胞的分化联系起来，并提供了新的机会，通过综合系统生物学方法更全面地探索这一调控网络在C4草中的功能。这些研究将包括几项新兴技术的开发和实施，包括细胞类型特定蛋白质组学、CRISPR/Cas9基因编辑技术、基于机器人的酵母一号杂交筛选、芯片序列、转化组学、X射线计算机断层成像、新的信息学/网络分析算法，以及发育表型和机制调控网络的建模。该项目产生的所有数据和资源将通过项目网站和长期储存库向公众开放。

PI: Thomas Brutnell [Donald Danforth Plant Science Center, (DDPSC)]CoPIs: Elizabeth Kellogg and Todd Mockler (DDPSC), Kimberly Gallagher (University of Pennsylvania), Chris Myers (Cornell University) and Joyce Van Eck (Boyce Thompson Institute for Plant Science)Senior Personnel: Robert Turgeon, Qi Sun, and Klaas van Wijk (Cornell University)Declining yields, increasing population growth and shifting climates are converging to create a perfect storm for agriculture. The looming threats to food security demand transformative innovations in agriculture that will drive the second green revolution. Maize is the most economically important crop in the U.S providing food, feed and bioenergy to the global economy. It is also one of the most photosynthetically productive plants on the planet. This productivity is driven by biochemical and anatomical adaptations associated with C4 photosynthesis. One proposed grand challenge is to introduce C4 traits into C3 crops such as rice and many temperate grasses. A major conceptual breakthrough in the understanding of the development of C4 photosynthesis was realized through the discovery that a root endodermal cell fate module was co-opted to drive a leaf specific cellular differentiation program. Importantly, a prediction from this model suggests that a limited number of changes in genes could lead to a major reprogramming of leaf cell fates. This project will test this prediction and expand on our understanding of the gene regulatory networks that drive both biochemical and anatomical innovations associated with C4 photosynthesis. The results of these studies will not only provide candidate genes for engineering C4 traits into C3 crops, but also provide novel targets for improvement of existing C4 crops such as maize, sugarcane and sorghum. With regard to training and outreach, the project will continue to expand on the MutantMillets outreach program at the DDPSC. MutantMillets provides teaching modules and teaching resources with hands-on activities in the plant sciences to engage high school students in the St. Louis metropolitan region. Importantly, all resources developed through this program will be portable to other school systems through the project website and through the educational networks established by the Education and Outreach Center at the DDPSC. Grasses that utilize C4 photosynthesis include maize, sorghum, sugarcane and Miscanthus. C4 grasses use two distinct cell types to create a CO2 pump that elevates the levels of CO2 in the vicinity of the enzyme Rubisco, effectively eliminating wasteful photorespiration. Under hot, dry conditions C4 systems display significantly increased productivity relative to C3 crops such as rice and wheat. This project aims to identify the foundational genetic and regulatory networks that control the differentiation of the two photosynthetic cell types in maize - the bundle sheath (BS) and mesophyll (M). This work expands on recent discoveries that has linked the SHR/SCR/IDD regulatory module to the differentiation of the BS and M cells of maize and provides new opportunities to more fully explore the function of this regulatory network in C4 grasses through an integrated systems biology approach. These studies will include the development and implementation of several emerging technologies including cell-type specific proteomics, CRISPR/Cas9 gene editing technologies, robotics-based yeast one hybrid screens, ChIP-seq, translatomics, X-ray computed tomography, novel informatics/network analysis algorithms, and modeling of both developmental phenotypes and mechanistic regulatory networks. All data and resources generated in this project will be made accessible to the public through the project website and through long-term repositories.