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

在大约30万种开花植物中，约有三分之一（如矮牵牛、金鱼龙、报春花、杜鹃花）的花瓣融合成管状结构，称为花冠管。花冠管包围和保护蜜腺和生殖器官。花冠管的长度、宽度和曲率的差异导致了各种各样形状各异的花朵，吸引了专门的传粉者群体（例如，猛犸象、飞蛾、蜂鸟、花蜜蝙蝠）。由于其在植物繁殖中的重要作用，花冠筒被认为是植物多样化和物种形成的关键形态创新。本研究利用猴花（Mimulus lewisii）这一新的遗传模式系统，对花冠管发育的相关基因进行了鉴定和表征，包括花冠管协调融合和花冠管形状多样性产生的相关基因。从这个项目产生的花图像、授粉视频和交互式多媒体插图将被纳入国内和国际公认的植物生物学部分。遗传学网站作为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助理、研究生和本科生，包括康涅狄格大学麦克奈尔学者项目中代表性不足的群体的成员。本研究利用最近开发的基因组资源、稳定的转基因工具和猴花（Mimulus）的化学诱导突变体来鉴定和表征控制花冠管形成的基因。研究人员实验室的初步工作结果为花冠管形成的发育遗传控制提供了一个新的概念模型。该模型的核心是生长素信号，它介导了最初分离的花瓣原基基部和原基间区域之间的协调生长。该核心模块的上游是控制花瓣原基横向扩展的遗传调控网络（GRN），本质上与控制叶的正面/背面极性和叶片生长的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。为了检验这些假设，将追求两个具体目标：(i)利用原位杂交、异位基因表达和RNA干扰模式物种Mimulus lewisii，确定叶片极性在花冠管形成过程中的主要调节因子的功能作用。（ii）通过对几个具有未融合花冠的路易斯菊非等位基因突变体的整体分离分析，确定控制花冠筒形成的GRN的其他成分。新发现的基因和已知的叶片极性调节因子之间的遗传相互作用将通过产生双或高阶组合突变体和转基因系来确定。对叶片极性调节基因的调控突变体和转基因系进行RNA-Seq分析，鉴定下游基因。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。

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.