Molecular Analysis of Chlamydomonas Mating-Type Locus

9513919好，这个项目的长期目标是分析单细胞绿藻莱茵衣藻性别分化的遗传控制。生物体在其生命周期过程中分化为4种不同的细胞类型，其中大部分(如果不是全部)由其交配型(Mt)基因座控制，该基因座以一对明显的等位基因存在。遗传mt+基因的细胞在氮饥饿条件下分化为正配子，只与互补的负等位基因发生交配相互作用和合子形成。这一建议的具体目标是：1.确定MID基因的基因产物是否负责指导配子发生过程中的mt性别分化，并确定它是直接作用还是与其他蛋白质协同作用，在此期间诱导负特定结构基因的转录。2.确定在特定品系中导致MID基因和大约20kb的侧翼DNA移动到常染色体位置的机制。当常染色体进入加性背景时，将进行进一步的工作以确定元素丢失的原因。3.近缘种金龟子MID基因的同源基因已被确定，并将进行实验以确定染色体位置和/或构型的相似性或差异性。将对其他更远亲的物种进行筛选，以保护MID基因的结构域。在配子发生过程中控制mt性别分化的基因已被确定为莱茵哈迪尔锥虫的中间基因，并将对其功能进行研究。该基因的染色体位置的影响也将通过与衣藻属密切相关的物种进行比较来研究，在衣藻属中，该基因位于非性别染色体上。基因的保护程度将通过对更远缘物种的筛选来确定。这些研究将加强我们对“早期”真核生物的性别分化是如何确定的理解。***

9513919 Goodenough The long range goal of this project is to analyze the genetic control of sexual differentiation in the unicellular green alga Chlamydomonas reinhardtii. The organism differentiates into 4 distinct cell types during the course of its life cycle and most, if not all, of these programs are governed by its mating-type (mt) locus which exists as a pair of apparent alleles. Cells inheriting the mt+ locus differentiate as plus gametes in response to nitrogen starvation and are capable of mating interactions and zygote formation only with complementary minus alleles. The specific goals of this proposal are: 1. To determine if the gene product of the mid gene is responsible for directing mt- sexual differentiation during gametogenesis and to determine if it acts directly or in concert with other proteins to elicit the transcription of minus- specific structural genes during that period. 2. To define the mechanisms responsible for the movement of the mid gene and about 20 kb of flanking DNA to an autosomal location in a specific strain of C. reinhardtii. Further work will be done to determine the cause for the loss of the element when the autosome is crossed into a plus background. 3. A homologue of the mid gene has been identified in C. incerta, a close relative and experiments will be done to determine similarities or differences in chromosomal location and or configurations. Other more distantly related species will be screened for conservation of the domains of the mid gene. %%% The mid locus of C. reinhardtii has been characterized as the gene responsible for directing mt- sexual differentiation during gametogenesis will be studied in respect to its function. The effect of chromosomal position of the gene will also be studied by comparison with a closely related species of Chlamydomonas where the gene is located on an non-sex chromosome. The level of conservation of the gene will be determined by screening of more distantly related species. These studies should enhance o ur understanding of how sexual differentiation is determined in an important representative of the "early" eukaryotes. ***