Co-option of cell cycle regulation for multicellular evolution

多细胞生物的进化是生物体形态的一个重大转变。然而，在任何生物群体中，多细胞的遗传基础还没有得到很好的理解。这个项目将利用多细胞绿色藻类作为模型真核生物，它们经历了最近已知的多细胞进化的例子。团藻是其中一种，它经常出现在大学课本和博物馆里，作为多细胞进化的主要例子。尽管多细胞进化对地球上的生命很重要，但这些生物中任何一种多细胞的遗传基础都是未知的。该项目的目标是通过研究这些生物体的细胞周期如何进化为多细胞生物来解决我们对多细胞进化知识的根本差距。 更广泛的影响活动将包括年轻的科学家的培训，从代表性不足的群体沿着与第一代大学生。该项目的中心假设是，从单细胞衣原体细胞周期调节已增选演变成多细胞在其未分化的多细胞相对生殖器。以前的实验表明，来自生殖细胞的视网膜母细胞瘤（RB）细胞周期阻遏物，当在单细胞衣原体中表达时，导致衣原体变成多细胞的，这表明细胞周期调控的进化协同选择对于多细胞性的进化是重要的。将采用两种方法来检验中心假设。首先，如何RB控制的细胞周期已经从单细胞衣原体发展到未分化的多细胞生殖器将被确定，以确定不同的调控基因相比，衣原体生殖器RB。第二，从第一种方法和比较基因组学中鉴定的生殖器中的候选多细胞性基因将在衣原体中功能获得和生殖器中功能丧失进行功能测试。总之，从方法的组合，该项目将推进我们对多细胞进化的遗传决定因素的理解。

The evolution of multicellularity is a major transition in organismal form. However, the genetic basis of multicellularity, in any group of organisms, is not well understood. This project will utilize multicellular green algae as model eukaryotes that have undergone the most recent known example of multicellular evolution. One member, Volvox, often appear in undergraduate texts and in museums as prime examples of multicellular evolution. Despite the importance of multicellular evolution for life on Earth, the genetic basis of multicellularity in any of these organisms is unknown. The goal of this project is to address this fundamental gap in our knowledge of multicellular evolution by examining how the cell cycles of these organisms have evolved for multicellularity. Broader Impact activities will include the training of young scientists from underrepresented groups along with first generation college students.The central hypothesis of this project is that cell cycle regulation from unicellular Chlamydomonas has been co-opted to evolve multicellularity in its undifferentiated multicellular relative Gonium. Previous experiments show that the retinoblastoma (RB) cell cycle repressor from Gonium, when expressed in unicellular Chlamydomonas, causes Chlamydomonas to become multicellular suggesting that evolutionary co-option of cell cycle regulation is important for the evolution of multicellularity. Two approaches will be used to test the central hypothesis. First, how RB control of the cell cycle has evolved from unicellular Chlamydomonas to undifferentiated multicellular Gonium will be determined to identify genes that are differently regulated by RB in Gonium compared to Chlamydomonas. Second, candidate multicellularity genes in Gonium identified from the first approach and from comparative genomics will be functionally tested for gain-of-function in Chlamydomonas and by loss-of-function in Gonium. In sum, from a combination of approaches, this project will advance our understanding of genetic determinants of multicellular evolution.