The effects of genome size reduction on cellular processes

人类基因组非常大，我们的基因包含非常长的非编码序列，称为内含子。适当的基因表达需要在信使rna翻译成蛋白质之前将内含子从信使rna中移除，而这项任务是由一种叫做剪接体的大型大分子细胞机器完成的。然而，并不是所有的基因组都很大。随着基因组的减少，内含子等非编码序列可能会缩短或丢失，复杂的细胞机器的尺寸也会缩小，组成成分也会减少。我建议用已知最小的核基因组来研究真核生物的剪接过程。识别不相关生物中减少剪接系统的共同特征可以预测剪接体的功能核心，并识别系统中的其他限制（如内含子序列特征），否则这些限制可能在更复杂的系统中被掩盖。

The human genome is very large, and our genes contain very long stretches of non-coding sequences called introns. Proper gene expression requires that introns be removed from messenger RNAs prior to their translation into proteins, and this task is carried out by a large, macromolecular, cellular machine called the spliceosome. However, not all genomes are large. As genomes are reduced, non-coding sequences such as introns can be shortened, or lost, and complex cellular machines are reduced in size and have fewer components. I propose to examine the process of splicing in eukaryotes with the smallest nuclear genomes known. Identifying common features of reduced splicing systems in unrelated organisms allows for predicting a functional core of the spliceosome, and identifies other constraints in the system (such as intron sequence features) that might otherwise be obscured in more complex systems. Microsporidia are unicellular, eukaryotic parasites that possess Nature's smallest non-organelle genomes and are my main study group. Although common parasites of animals, genomes are characterized for only a small number of species. In an attempt to increase our understanding of genome diversity within the group, and broaden our understanding of host-parasite relationships, I propose to characterize the infection pattern, and genome and transcript architecture of a new microsporidian parasite of nematodes (microscopic round worms). Understanding organismal diversity is key to comprehending life on this planet, and understanding the underlying diversity at the cellular level is just as crucial. By investigating the flexibility of a key eukaryotic process in a cellular system that is highly reduced, yet still functions, we can gain mechanistic understanding. This research impacts the fields of evolutionary genetics, molecular parasitology, splicing biochemistry and microbial genomics.