Collaborative Research: The Aquilegia Petal as a Model for the Elaboration and Evolution of Organ Shape

植物的身体只由几个重复产生的结构组成，如叶和茎。然而，无论是在个体内部还是在不同物种之间，这些结构的形状都可能以可预测的、一致的方式发生巨大变化。这种形状的变化由细胞分裂和细胞形状的组合控制，而细胞分裂和细胞形状又必须由基因表达的变化控制。这项拟议的研究试图确定复杂的形状是如何在发育过程中产生的，以及控制这些过程的基因。因此，这项研究将解决生物体如何实现其身体形状的基本问题，这对它们的生存至关重要。这项研究还将通过培训年轻科学家，包括本科生、研究生和博士后研究员，通过外联努力招募女性和代表性不足的少数群体，从而产生更广泛的影响。花蜜刺是一种复杂的三维结构，是最近衍生出来的，在物种之间高度可变，因此可以作为一个强大的模型来研究复杂器官形状的控制和进化。花蜜刺通过局部定向细胞分裂的早期阶段发展，形成预先形成图案的刺杯，随后是一段高度不稳定的细胞伸长阶段，最终形成刺的长度和形状。在近缘种和干扰种中，短刺长度和形状的变化是通过改变几个发育参数来产生的：长度主要由细胞各向异性控制，而细胞各向异性又由细胞伸长的持续时间控制；曲率是通过改变短刺远端和近端之间的细胞伸长来产生的；周长是由细胞各向异性和细胞数量在径向方向上的变化控制的。因此，了解侧枝的发育和进化将提供对侧器官发育的所有这些基本方面的洞察，这可以为更广泛地研究被子植物的侧器官的进化提供新的视角。这项拟议的研究试图整合来自发育遗传学、进化基因组学/遗传学和生物物理学领域的多个研究方向。具体地说，该项目将阐明花瓣短刺发育的基本遗传控制，探索激素信号和生物力学应变在控制短枝发育中的作用，使用基于QTL的方法来确定与短枝形状多样化有关的基因，并使用比较基因组方法来确定与花蜜短刺起源相关的选择性扫描。

The body of a plant is made of just a few repeatedly produced structures, such as leaves and stems. However, these structures can vary tremendously in their shape both within an individual and between different species in predictable, consistent ways. This variation in shape is controlled by a combination of cell division and cell shape, which in turn must be controlled by variation in gene expression. The proposed research seeks to determine how complex shapes arise through development and the genes that control these processes. Thus this research will address the fundamental question of how organisms achieve the shapes of their bodies, which is critical to their survival. This research will also have broader impacts through the training of young scientists including undergraduates, graduate students and postdoctoral fellows with outreach efforts to recruit female and underrepresented minorities. The nectar spur of Aquilegia is a complex three-dimensional structure that is recently derived and highly variable among species and, thus, can serve as a powerful model for investigating the control and evolution of complex organ shape. Nectar spurs develop via an early phase of localized, oriented cell divisions that create the prepatterned spur cup, which is then followed by a period of highly anisotopic cell elongation that gives rise to the final length and shape of the spur. Among the closely related and interfertile species of Aquilegia, variation in spur length and shape is generated by changing several developmental parameters: length is primarily controlled by cell anisotropy, which is in turn controlled by the duration of cell elongation; curvature is generated by varying cell elongation between the distal vs. proximal compartments of the spur; and circumference is controlled both by changes in cell anisotropy and cell number in the radial orientation. Thus, understanding the development and evolution of Aquilegia spurs will provide insight into all of these fundamental aspects of lateral organ development, which can provide new perspectives on the evolution of lateral organs more broadly across the angiosperms. The proposed research seeks to integrate multiple lines of study drawn from the fields of developmental genetics, evolutionary genomics/genetics, and biophysics. Specifically, the project will elucidate the fundamental genetic control of petal spur development, explore the roles of hormonal signaling and biomechanical strain in controlling spur development, use QTL-based approaches to identify the genes involved in the diversification of spur shape and use comparative genomic approaches to identify selective sweeps associated with the origin of nectar spurs.