Collaborative Research: Dynamic zonation in the plant root

植物的根在土壤中生长，从而在寻找营养和水分的同时固定植物。生长中的根尖分为两个主要区域：分生组织区，为根体产生新细胞;伸长区，细胞迅速伸长，从而推动根尖穿过土壤。分离成这些功能性生长区是复杂的，因为这些区的边缘处的细胞改变了身份;也就是说，分生组织细胞变成伸长细胞，伸长细胞变成成熟细胞。因此，这些区域本质上是动态的，但保持其位置。此外，由于根对温度等因素作出反应，这些区域的长度、生长速度和细胞数量都会发生变化。一个有趣的问题是，根如何保持区域的完整性和稳定性，尽管潜在的细胞动力学。这个问题正在通过实验解决，使用遗传方法和温度变化来研究根部的反应，对生长进行成像并量化过程。这些研究将有助于解释这些区域是如何建立和调节的，提供有关根系生长机制和恢复力的基础知识。这些结果可以提供新的工具，通过培育更具弹性的根系反应来修改根系生长，并可以为预测温度变化对根系行为的影响提供基线信息。本科生将接受培训，并将获得跨学科方法的技能和经验，将工程学与生物学相结合，以解决科学问题。为了了解稳定区如何从动态细胞中出现，该项目使用拟南芥适应温度。在研究根的热形态发生时，首席研究员巴斯金发现，尽管根在25ºC下比在15º C下生长得更快，但生长区的长度相同，皮层以相同的速度产生细胞。因此，生长区长度和皮层细胞生产速率适应以抵消温度对反应的加速。有趣的是，适应的细胞生产率是特定于皮层：表皮产生细胞在温暖的温度更快。此外，当细胞分裂抑制剂在皮质中表达而在其他组织中不表达时，生长区被截短。该项目的目的首先是阐明热形态建成过程中调节根分区的途径。通过比较15 ℃和25 ℃，研究小组将筛选现存的突变体，确定相关基因是否直接作用于根，并获得特异性用于表皮和皮层的转录组。第二个目的是阐明皮层在根的分区中的作用。抑制细胞分裂的基因将从特定组织中的诱导型启动子表达;然后，分裂、延伸和核内复制将被定量为温度的函数。第三个目标将使用先进的图像分析来量化两种温度下整个分生组织的细胞分裂速率，显然是第一次解决不同组织中的分裂行为。总体而言，该项目结合了生长调节途径的分子解剖和细胞行为的定量分析，以表征生命系统的层次结构。该奖项反映了NSF的法定使命，并通过使用基金会的智力价值和更广泛的影响审查标准进行评估，被认为值得支持。

Plant roots grow through the soil, thereby anchoring the plant while foraging for nutrients and water. The growing root tip is divided into two main regions: the meristem zone, which produces new cells for the root body, and the elongation zone, where cells elongate rapidly, thus propelling the root tip through the soil. The separation into these functional growth zones is complicated by the fact that cells at the edges of the zones change identity; that is, meristem cells become elongating cells and elongating cells become mature cells. These zones are therefore inherently dynamic, yet retain their location. In addition, as the root responds to factors such as temperature, the zones change in length, growth rate, and cell number. An intriguing question is how the root maintains the integrity and stability of the zones despite the underlying cell dynamics. This question is being addressed experimentally using genetic methods and temperature changes to study responses of the root, image the growth and quantify the processes. These studies will help explain how the zones are established and regulated, providing fundamental knowledge about the mechanisms and resilience of root growth. The outcomes could provide access to new tools for modifying root growth through breeding more resilient root responses and could provide baseline information for predicting impacts of temperature change on root behavior. Undergraduate students will be trained and will gain skills and experience in interdisciplinary approaches that integrate engineering with biology to solve scientific problems.To understand how stable zones emerge from dynamic cells, this project uses Arabidopsis thaliana acclimating to temperature. Investigating thermomorphogenesis in roots, principal investigator Baskin found that although the root grows faster at 25ºC compared to 15ºC, the growth zone has the same length and the cortex produces cells at the same rate. Thus, growth zone length and cortical cell production rate acclimate to counteract the acceleration of reactions by temperature. Interestingly, acclimated cell production rate is specific to cortex: epidermis produces cells faster at the warmer temperature. Also, the growth zone is truncated when an inhibitor of cell division is expressed in the cortex but not when expressed in other tissues. The project aims first to elucidate the pathway regulating root zonation during thermomorphogenesis. Comparing 15 and 25ºC, the team will screen extant mutants, determine whether implicated genes act in the root directly, and obtain transcriptomes specifically for epidermis and cortex. The second aim is to elucidate the role of the cortex in root zonation. Genes that inhibit cell division will be expressed from inducible promoters in specific tissues; then, division, elongation, and endoreduplication will be quantified as a function of temperature. The third aim will use advanced image analysis to quantify cell division rates throughout the meristem at both temperatures, resolving, apparently for the first time, division behavior in separate tissues. Overall, the project unites molecular dissection of growth-regulating pathways with quantitative analysis of cellular behavior to characterize the hierarchical organization of a living system.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.