Molecular Analysis of Chlamydomonas Mating-Type Locus

减数分裂真核生物的性行为被认为起源于至少6亿年前。 它最常见的表现形式发生在多细胞植物和动物的生殖系组织中，但大多数现代单细胞真核生物，包括酵母，纤毛虫和藻类，也参与减数分裂性，并且假定减数分裂性首先出现在单细胞中，并为多细胞的进化提供了基础。 由于性和物种形成是密切交织在一起的，对生物多样性的理解在很大程度上取决于对性策略如何运作和进化的理解。 该项目的重点是两种密切相关的单细胞绿色藻类，莱茵衣藻和不定衣藻，具有非常相似的“管家基因”，但其性别相关基因是高度分歧的。 NSF先前的支持使该实验室能够鉴定和克隆这些生物体中控制性分化和受精卵成熟的基因，包括关键交配型基因座中的基因。 本项目将继续分析它们的功能及其演变。 该项目的重点是三个基因。 1)Mid基因产物诱导细胞分化为交配型负分化途径并抑制正分化途径;设计实验以鉴定参与Mid蛋白影响这种转录调控的蛋白质。 2)Iso 1基因编码ISWI家族中的一种染色质重塑因子，该因子在氮饥饿（启动性分化的环境信号）时上调，并且是配子相关基因表达所必需的;实验旨在了解其调控模式、靶基因及其与Mid表达的关系。 3)Gsp 1基因产物参与配子细胞融合后合子特异性基因的表达;实验旨在了解这种转录调控是如何影响的。

Meiotic eukaryotic sex is thought to have originated at least 600 million years ago. Its most familiar manifestations occur in the germ-line tissues of multicellular plants and animals, but most modern single-celled eukaryotes, including yeasts, ciliates, and algae, also engage in meiotic sex, and it is assumed that meiotic sex first arose in unicells and provided the basis for the evolution of multicellularity. Since sex and speciation are intimately intertwined, an understanding of biodiversity is critically dependent on an understanding of how sexual strategies operate and evolve. This project is focused on two closely related species of unicellular green algae, Chlamydomonas reinhardtii and Chlamydomonas incerta, that have very similar "housekeeping genes" but whose sex-related genes are highly divergent. Previous support from the NSF has enabled this laboratory to identify and clone genes that govern sexual differentiation and zygote maturation in these organisms, including genes resident in the key mating-type locus. The current project will continue the analysis of their function and their evolution. The project focuses on three genes. 1) The Mid gene product induces cells to differentiate as mating-type minus and suppresses the plus differentiation pathway; experiments are designed to identify proteins that participate with the Mid protein in effecting this transcriptional regulation. 2) The Iso1 gene encodes a chromatin-remodeling factor in the ISWI family that is up-regulated in response to nitrogen starvation -- the environmental signal that initiates sexual differentiation -- and is necessary for expression of gamete-related genes; experiments are designed to understand its mode of regulation, its target genes, and its relationship to Mid expression. 3) The Gsp1 gene product is involved in the expression of zygote-specific genes following gametic cell fusion; experiments are designed to understand how this transcriptional regulation is effected.