Evolution of Sexually Dimorphic Germ Cells in Volvox carteri

描述(申请人提供)：摘要。这项工作的长期目标是了解导致发育复杂性的分子遗传机制。在生命的历史上，多细胞生物经历了多次进化，并导致了真核生物多样性的爆炸性增长，包括新的生殖策略。性别二型性和多细胞在几个谱系中共同进化，但导致它们在动物和植物中共同进化的机制存在于遥远的过去，目前尚不清楚。Volvox carteri是一种多细胞绿藻，与其最近的单细胞近亲Chlamydomonas rehardtii有着共同的祖先。从衣藻的单细胞祖先，卡特里弧菌进化出许多后生动物的特征，包括完全的生殖体分离和性别二型性发育。在性别分化过程中，卡氏弧菌雌性产生卵子，雄性产生精子，这一特征由带有两个等位基因的交配型(Mt)基因座控制，mtf(雌性)和mtm(雄性)。编码卡氏弧菌mt的基因组区域已被鉴定和部分鉴定，导致以下目的：(I)克隆和测序mt的两个等位基因；(Ii)使用注释和转录图谱来确定性别决定的关键调控因素；(Iii)鉴定负责性别二态发育的基因，包括vMATS，一种与mt连锁的视网膜母细胞瘤(Rb)肿瘤抑制同源基因，它在Carteri V.carteri雄性和雌性之间高度多态；(Iv)通过异位表达和基因失活实验，直接测试雌性和雄性vMATS亚型和其他潜在的性别决定基因在调节性别分化中的作用。卡特里弧菌交配基因座的发现为剖析性别二型性进化的分子遗传变化和了解性染色体如何进化影响发育编程提供了一个前所未有的机会。关联性。生殖细胞对人类生殖健康至关重要，也与某些形式的人类癌症有关，但人们对它们的生物学了解很少。这里提出的这项工作有望揭示导致在一个简单的模型系统中产生卵子和精子的潜在遗传结构，并已经发现了人类肿瘤抑制因子和生殖细胞形成之间潜在的保守联系。

DESCRIPTION (provided by applicant): SUMMARY. The long-term goal of this work is to understand the molecular genetic mechanisms that underlie developmental complexity. Multicellularity has evolved multiple times in the history of life and has led to an explosion of eukaryotic diversity, including novel reproductive strategies. Sexual dimorphism and multicellularity have coevolved in several lineages, but the mechanisms that led to their co-evolution in animals and plants lie in the distant past and are unknown. Volvox carteri is a multicellular green alga that shares recent common ancestry with its closest unicellular relative, Chlamydomonas reinhardtii. From a single-celled Chlamydomonas ancestor V. carteri has evolved many metazoan-like features including complete germ-soma separation and sexually dimorphic development. During sexual differentiation V. carteri females produce eggs and males produce sperm, a trait that is controlled by a mating type (mt) locus with two alleles, mtf (female) and mtm (male). The genomic region that encodes V. carteri mt has been identified and partially characterized, leading to the following Aims: (i) Clone and sequence both alleles of mt; (ii) Use annotation and transcriptional profiling to identify key regulators of sex determination; (iii) Characterize the genes that are responsible for sexually dimorphic development including vMATS, a mt-linked retinoblastoma (RB) tumor suppressor homolog that is highly polymorphic between V. carteri males and females; (iv) Directly test the role of female and male vMATS isoforms and other potential sex determining genes in regulating sexual differentiation by using ectopic expression and genetic inactivation experiments. The discovery of the V. carteri mating locus provides an unprecedented opportunity to dissect the molecular genetic changes that underlie the evolution of sexual dimorphism and to understand how sex chromosomes evolve to influence developmental programming. RELEVANCE. Germ cells are critical for human reproductive health and are also associated with some forms of human cancer, but their biology is poorly understood. The work proposed here is expected to reveal the underlying genetic architecture that leads to the production of eggs and sperm in a simple model system, and has already uncovered a potentially conserved link between a human tumor suppressor and germ cell formation.