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

鉴于生殖是进化成功的关键，支配花发育的生物学规则是至高无上的。虽然大多数开花植物只开出完好的花(既有雄花又有雌花的花)，但大约30%的物种产生不完美的花，其中有雄花(雄花)或雌花(有心皮)。不完美的花与风媒授粉和异交增加有关。尽管其他农业驯化的草本植物(例如，水稻、小麦、谷子、高粱)开出完美的花朵，玉米在同一植株上形成分开的雄花和有心皮的花序。分离的雄花序和雌花序使植物育种计划能够产生具有高产雌花序和F1杂交种的优秀、适应性强的玉米品种。这项研究拨款将通过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近缘物种高粱的完美花序，2)通过激素水平和分子生物学的分析来鉴定新的花突变体，3)通过将发育转录与激素反应遗传途径相结合来鉴定参与完美和不完美花发育的候选基因，从而采用多层次的组织来研究玉米的花特征。从这项工作中获得的知识将为通过基因、激素和发育进化过程的协调活动在谷类物种中如何产生生殖结构提供重要的见解，并将使人们能够预测哪些基因可以用于操纵其他作物的花的二型性。通过对雄花和雌花特征改变的玉米突变体的分析，似乎至少有三种激素JA、GA和BR对玉米雄花和心皮花的指定是必需的，通常调节雄花中的雌蕊败育。在目标1中，玉米穗发育的转录个体发育将与雄穗和高粱圆锥花序发育的个体发育进行比较。将确定独特的男性和女性节目。在目标2中，将分析两个新的突变体，FUN和TE2。它们与先前描述的花序突变体不同，可能为分离的雄花序和雌花序的进化提供新的线索。与JA、BR或microRNA的雄穗突变体相比，这两个突变体的雄穗具有更多的雌性结构。它们不编码荷尔蒙途径中的酶，也不直接涉及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TE2的下游靶标，将扩大花序决定因子的网络。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相结合，以制定协调不完美花朵进化的生命规则。尽管研究预计不完美的花有多种进化起源，但已知的调节器官流产的发育机制是有限的，因此共同规范的遗传网络可能是可能的。考虑到这一点，协调玉米花卉二形性的规则可能适用于其他草本植物和被子植物。这一奖项反映了NSF的法定使命，并通过使用基金会的智力优势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.