COLLABORATIVE RESEARCH: Genetic network evolution in grass abscission zones

农业依赖于在收获前保留种子的植物，而野生植物需要在一个被称为破碎或脱落的过程中丢弃种子。因此，小麦、水稻和玉米等谷类作物的驯化是人类选择不会破碎的自发突变植物的结果。在面临人口快速增长和气候变化的世界中，重要的是了解粉碎的机制，以便能够驯化和改良新的野生或较少驯化的谷类作物，从而使食物选择多样化，并在边缘环境中改善农业。这个项目将研究破碎过程，这是由一组特殊的细胞控制的，称为离散区(AZ)。AZ的细胞发育将在不同的谷类作物及其野生近缘作物中进行比较，包括珍珠、小米和高粱这两种具有经济价值和耐旱的谷物。该项目旨在确定功能性AZ所需的基因，并了解这些基因的修改如何导致不同物种AZ的形态差异。高中生、本科生和中学教师将参与进行这项研究。提供给中学教师的研究经验将用于制定新的教案，并进一步影响下一代科学教育。随着进化时间的推移，基因调控网络不断地被修改，但修改的速度和变化的性质通常是未知的。该项目涉及控制植物离区(AZ)的网络的变化速度和模式，AZ是一种特殊的细胞层，允许植物脱落种子、果实、花瓣或叶子。三种远缘关系的草本植物(杂草水稻、短穗狗尾草和狗尾草)的AZ由不同的基因组控制，这表明潜在的遗传网络重新布线。该项目将调查草亚科Panicoideae中其他物种之间的AZ网络，包括野生和栽培珍珠谷子(Cichrus americanus，与狗尾草关系密切)和高粱(高粱)，后者是更远的亲戚。组织学(使用光学和透射电子显微镜)和基因表达模式(RNA-seq)将在发育的几个阶段进行表征。为了确定广泛的重新连接是否来自顺式调控模块的变化，两个保守的转录因子YAB2/SH1和MYB26的上游和下游调控因子将在遗传易受控制的物种狗尾草和Brachypodium中进行表征，结合突变分析、RNA-seq、DAP-seq和生物信息学。为了确定不同的早期调控网络是否收敛于一组保守的晚期遗传相互作用，将在脱落之前和之后评估转录、酶和细胞壁的变化。总而言之，这些数据将决定调控AZ形成的基因网络随着时间的推移如何以及以多快的速度重塑。高中学生和教师将参与植物表型鉴定的许多方面。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。

Agriculture depends on plants that hold on to their seeds until harvest, yet wild plants need to drop their seeds, in a process known as shattering or abscission. Therefore, domestication in cereal crops such as wheat, rice, and corn was the result of human selection for spontaneous mutant plants that did not shatter. In a world facing rapid population growth and changing climates, it is crucial to understand the mechanism of shattering to be able to domesticate and improve new wild or less domesticated cereal crops, thereby diversifying food choices and improving agriculture in marginal environments. This project will examine the shattering process, which is controlled by a specialized set of cells known as an abscission zone (AZ). Cell development of the AZ will be compared in different cereal crops and their wild relatives, including pearl millet and sorghum, two economically valuable and drought tolerant cereals. The project aims to identify genes that are required for a functional AZ, and to understand how modification of these genes causes morphological differences in the AZ in different species. High school students, undergraduates and secondary school teachers will be involved in conducting the research. The research experience provided to secondary school teachers will be used to develop new lesson plans, and further impact next generation education in science. Gene regulatory networks are continually modified over evolutionary time, but the speed of modification and the nature of the changes are generally not known. This project addresses both the tempo and mode of change in the network controlling the abscission zone (AZ) in plants, a specialized cell layer that permits plants to drop seeds, fruits, petals or leaves. The AZ of three distantly related grass species (weedy rice, Brachypodium, and Setaria) is controlled by distinct sets of genes, suggesting rewiring of the underlying genetic network. This project will investigate the AZ networks among additional species in grass subfamily Panicoideae, including wild and cultivated pearl millet (Cenchrus americanus, closely related to Setaria) and sorghum (Sorghum bicolor), a more distant relative. Histology (using light and transmission electron microscopy) and gene expression patterns (RNA-seq) will be characterized at several stages of development. To determine whether the extensive rewiring comes from changes in cis-regulatory modules, the upstream and downstream regulators of two conserved transcription factors, YAB2/SH1 and MYB26, will be characterized in the genetically tractable species Setaria and Brachypodium, with a combination of mutant analysis, RNA-seq, DAP-seq and bioinformatics. To determine if the disparate early regulatory networks converge on a conserved late stage set of genetic interactions, transcriptomic, enzymatic, and cell wall changes will be evaluated right before and after abscission. Together, these data will determine how and how fast the gene network regulating AZ formation is remodeled over time. High school students and teachers will be involved in many aspects of plant phenotyping.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.