Developmental Genetics of Corolla Tube Formation: A Key Morphological Innovation During Angiosperm Evolution

大约30万种开花植物中有三分之一（例如，矮牵牛、金鱼草、报春花、杜鹃花）产生花瓣融合成管状结构（称为花冠筒）的花。花冠筒包围并保护蜜腺和生殖器官。花冠筒的长度、宽度和曲率的差异导致了无穷无尽的不同形状的花朵，吸引了专门的传粉者群体（例如，牛虻、天蛾、蜂鸟、花蜜蝙蝠）。由于其在植物繁殖中的重要性，花冠筒被认为是有助于植物多样化和物种形成的关键形态创新。本研究采用了一种新的遗传模型系统，monkeyflowers（Mimulus lewisii），以确定和表征基因负责花冠筒的发展，包括基因负责协调器官融合和产生的多样性花冠筒形状。该项目产生的花卉图像、授粉视频和互动多媒体插图将被纳入国家和国际公认的Learn.Genetics网站的新植物生物学部分，作为K-16学生的在线教育资源。遗传学、发育和进化方面的多学科培训包括博士后、研究生和本科生，包括参加康涅狄格大学麦克奈尔学者计划的代表性不足群体的成员。这项研究利用最近开发的基因组资源、稳定的转基因工具和化学诱导的突变体猴花（Mimulus）来识别和表征控制花冠管形成的基因。在研究者的实验室的初步工作的结果允许制定一个新的概念模型的发展遗传控制花冠筒的形成。该模型的核心是生长素信号，它介导最初分离的花瓣原基和原始区域之间的协调生长。该核心模块的上游是控制花瓣原基的侧向扩展的遗传调控网络（GRN），基本上与控制叶近轴/远轴极性和叶片生长的GRN相同。这个核心模块的下游是器官边界基因，如果不受生长素信号的抑制，它们会抑制局部组织的生长。两个具体的目标将追求测试这些假设：（一）确定功能的作用，主要调控叶极性的花冠管形成，利用原位杂交，异位基因表达，RNA干扰的模式物种Mimulus lewisii。(ii)通过大量分离分析几个额外的非等位基因突变体的M。Lewisii具不愈合的花冠。新鉴定的基因和已知的叶极性调节基因之间的遗传相互作用将通过产生双或更高阶的组合突变体和转基因株系来确定。该奖项反映了NSF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。

About one third of the ~300,000 flowering plant species (e.g., petunia, snapdragon, primrose, rhododendron) produce flowers with petals fused into a tubular structure referred to as the corolla tube. The corolla tube encloses and protects the nectaries and reproductive organs. Differences in the length, width, and curvature of the corolla tube have led to an endless variety of differently shaped flowers that attract specialized groups of pollinators (e.g., beeflies, hawkmoths, hummingbirds, nectar bats). Because of its importance in plant reproduction, the corolla tube is considered a key morphological innovation that contributes to plant diversification and speciation. This study employs a new genetic model system, monkeyflowers (Mimulus lewisii), to identify and characterize the genes responsible for corolla tube development, including the genes responsible for coordinated organ fusion and the generation of a diversity of corolla tube shape. The flower images, pollination videos, and interactive, multimedia illustrations resulting from this project will be incorporated into a new Plant Biology section on the nationally and internationally recognized Learn.Genetics website as online educational resources for K-16 students. Multi-disciplinary training in genetics, development, and evolution includes post-doctoral associates, graduate students and undergraduate students, including members of under-represented groups enrolled in the McNair Scholars Program at UConn.This study leverages recently developed genomic resources, stable transgenic tools, and chemically induced mutants of monkeyflowers (Mimulus) to identify and characterize genes that control corolla tube formation. Results from preliminary work in the investigator's laboratory allows the formulation of a new conceptual model for the developmental genetic control of corolla tube formation. At the heart of the model is auxin signaling that mediates coordinated growth between the bases of the initially separate petal primordia and the inter-primordial regions. Upstream of this core module is the genetic regulatory network (GRN) controlling lateral expansion of the petal primordia, essentially the same GRN that controls leaf adaxial/abaxial polarity and lamina growth. Downstream of this core module lie the organ boundary genes that suppress localized tissue growth if not repressed by auxin signaling. Two specific aims will be pursued to test these hypotheses: (i) Determine the functional roles of the major regulators of leaf polarity in corolla tube formation using in situ hybridization, ectopic gene expression, and RNA interference in the model species Mimulus lewisii. (ii) Identify additional components of the GRN controlling corolla tube formation by bulk segregant analyses of several additional non-allelic mutants of M. lewisii with unfused corollas. Genetic interactions among the newly identified genes and the known leaf polarity regulators will be determined by generating double or higher order combinatorial mutants and transgenic lines. RNA-Seq analyses of selected regulatory mutants and transgenic lines of the leaf polarity regulators will be conducted to identify downstream genes.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.