COLLABORATIVE RESEARCH: Genetic network evolution in grass abscission zones

农业依赖于植物在收获前保持种子，然而野生植物需要在一个被称为破碎或脱落的过程中落下种子。因此，谷类作物如小麦、水稻和玉米的驯化是人类选择自发突变植物的结果，这些植物不会破碎。在一个面临人口快速增长和气候变化的世界中，了解破碎的机制至关重要，以便能够驯化和改进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改善边缘环境中的农业。这个项目将研究粉碎过程，这是由一组专门的细胞称为一个粉碎区（AZ）控制。AZ的细胞发育将在不同的谷类作物及其野生亲缘植物中进行比较，包括珍珠粟和高粱，这两种经济上有价值的耐旱谷物。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饰如何导致不同物种AZ的形态差异。高中生、大学生和中学教师将参与这项研究。为中学教师提供的研究经验将用于制定新的课程计划，并进一步影响下一代的科学教育。基因调控网络在进化过程中不断修改，但修改的速度和变化的性质通常是未知的。该项目解决了控制植物中释放区（AZ）的网络的变化速度和模式，AZ是一种特殊的细胞层，允许植物落下种子，果实，花瓣或叶子。三个远亲草种（杂草稻、短柄草和狗尾草）的AZ由不同的基因组控制，这表明潜在的遗传网络发生了重新布线。该项目将调查禾本科Panicoideae中其他物种之间的AZ网络，包括野生和栽培的珍珠粟（Cenchrus americanus，与Setaria密切相关）和高粱（Sorghum bicolor），一种更远的亲戚。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布线是否来自顺式调控模块的变化，两个保守的转录因子，YAB 2/SH 1和MYB 26的上游和下游调节器，将其特征在于在遗传上易处理的物种狗尾草属和短柄草属，与突变体分析，RNA-seq，DAP-seq和生物信息学的组合。为了确定不同的早期调控网络是否汇聚在一组保守的晚期遗传相互作用上，将在终止之前和之后评估转录组学、酶和细胞壁变化。总之，这些数据将决定如何以及如何快速的基因网络调节AZ形成重塑随着时间的推移。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。

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.