Understanding the evolution of dimorphic flowers in maize through combined changes in transcriptional dynamics, hormone levels and genetic networks

考虑到繁殖对进化成功至关重要，支配花发育的生物学规则是至关重要的。虽然大多数开花植物只产生完美的花（具有雄性和雌性结构的花），但大约30%的物种产生不完美的花，其中有雄性（雄花）或雌性（心皮）花。不完美的花与风授粉和增加异交有关。虽然其他农业驯化植物在草（例如。水稻，小麦，小米，高粱）产生完美的花，玉米形成单独的，雄花和心皮花序在同一植株上。单独的雄性和雌性花序使植物育种计划能够产生具有高产雌性花序和F1杂种的优良、适应性玉米品种。这项研究资助将采用多层次的组织来研究玉米的花特征，方法是：1）比较玉米雄花和心皮花序发育过程中转录动力学的保守性与密切相关的物种高粱的完美花序，2）通过分析激素水平和分子生物学来表征新的花突变体，3）通过整合发育转录组学与花反应遗传途径来鉴定参与完美花和不完美花发育的候选基因。从这项工作中获得的知识将提供重要的洞察力，了解谷物物种的生殖结构是如何通过基因、激素和发育进化过程的协调活动产生的，并将允许人们预测哪些基因可用于操纵其他作物的花二型性。通过对具有改变的雄性和雌性花特征的玉米突变体的分析，似乎至少有三种激素，JA，GA，和BR是玉米雄花和心皮花发育所必需的，常调节雄花雌蕊败育。在目标1中，将发育中的玉米穗的转录个体发生与发育中的雄穗和高粱穗的个体发生进行比较。将确定独特的男性和女性方案。在目标2中，将分析两个新的突变体fun和Te2。它们不同于先前描述的花序突变体，并可能为单独的雄性和雌性花序的进化提供新的线索。两者的雄穗比JA、BR或microRNA雄穗突变体具有更多的雌性结构。它们不编码激素途径中的酶或直接涉及microRNA。FUN是一种功能未知的核定位蛋白。 TE2是一种ARF转录因子。通过确定FUN的相互作用伙伴和TE 2的下游靶标，花序决定因子的网络将得到扩展。 目标3的目标是将目标1和目标2的方法与其他公共数据集结合起来，制定协调不完美花朵进化的生命规则。 虽然研究预期不完美花的多个进化起源，但已知的调节器官败育的发育机制是有限的，因此可能存在共同的规格遗传网络。考虑到这一点，协调玉米花二型性的规则可能适用于其他禾本科植物和被子植物。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。

The biological rules that govern floral development are paramount, given that reproduction is critical to evolutionary success. Although most flowering plants produce only perfect flowers (those with both male and female structures), roughly 30% of species produce imperfect flowers, which have with either male (staminate) or female (carpellate) flowers. Imperfect flowers are associated with wind-pollination and increased outcrossing. Although other agriculturally domesticated plants in the grasses (ex. rice, wheat, millet, sorghum) produce perfect flowers, maize forms separate, staminate and carpellate inflorescences on the same plant. Separate male and female inflorescences have allowed plant breeding programs to generate elite, adapted maize varieties with highly productive female inflorescences and F1 hybrids. This research grant will employ multiple levels of organization to investigate floral characteristics in maize by 1) comparing the conservation of transcriptional dynamics during the development of staminate and carpellate inflorescences in maize with the perfect inflorescences of the closely related species, sorghum, 2) characterizing new floral mutants through analysis of hormone levels and molecular biology, 3) identifying candidate genes involved in the development of perfect and imperfect flowers by integrating developmental transcriptomics with hormone-responsive genetic pathways. Knowledge gained from the work will provide important insight into how reproductive structures are generated in cereal species through the coordinated activity of genes, hormones, and developmental evolutionary processes and will allow one to predict which genes can be used for manipulating floral dimorphism in other crops.Through analysis of maize mutants with altered male and female floral characteristics, it appears that at least three hormones, JA, GA, and BR, are necessary for specification of staminate and carpellate flowers in maize, often regulating pistil abortion in male flowers. In Aim 1, a transcriptional ontogeny of developing maize ears will be compared to the ontogeny of developing tassels and sorghum panicles. Unique male and female programs will be identified. In Aim 2, two new mutants, fun and Te2, will be analyzed. They are different than previously described inflorescence mutants and may provide new clues to the evolution of separate male and female inflorescences. The tassels of both have a more female architecture than the JA, BR or microRNA tasselseed mutants. They do not encode enzymes in hormone pathways or directly involve microRNAs. FUN is a nuclear localized protein of unknown function. TE2 is an ARF transcription factor. By identifying the interacting partners of FUN and the downstream targets of TE2, the network of inflorescence determination factors will be expanded. The goal of Aim 3 is to combine the approaches of Aims 1 and 2 alongside other public datasets to formulate rules of life that coordinate the evolution of imperfect flowers. Although research expects multiple evolutionary origins of imperfect flowers, known developmental mechanisms regulating organ abortion are limited and thus common specification genetic networks may be possible. With that in mind, the rules of rule that coordinate floral dimorphism in maize may apply to other grasses and angiosperms in general.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.