Molecular evolution of green algae

在过去的几十年里，我的实验室一直在研究绿藻，这是陆地植物的起源。我们的主要工作重点是细胞器基因组，即线粒体和叶绿体中的基因组，它们分别是呼吸和光合作用的位点，但我们也一直在研究小组中解决与核基因组（细胞的主要基因组）相关的问题。我们努力的首要主题是记录和解释绿藻和陆地植物基因组特征的多样性。对于细胞器基因组，这包括一些变量，如完整的还是碎片化的，圆形的还是线性的，富含gc的还是富含at的，紧凑的还是臃肿的，对于核基因组，它的非编码DNA的部分是最近的质体和线粒体起源。我们还估计了绿色植物（藻类和陆生植物）三个遗传区室中沉默（非编码）位点的相对突变率和核苷酸多样性水平，并用这些来解释这一群体成员基因组结构的差异。下一个资助期的工作主要集中在四项主要活动上：(1)对多聚藻枝进行更广泛的采样和表征，多聚藻枝是一组绿藻，现在是无色的，已经失去了光合作用和细胞壁合成的能力——尽管过去曾描述过北美和南美的分离株，但目前所有这一重要属的菌株都来自欧洲；(2)多tomella光合作用次生损失的进化——通过与其近亲多tomella的质体蛋白质组学比较，可以了解模式藻莱茵衣藻的基本光合功能；(3) Volvox和Polytomella线粒体基因组结构的进化；(4)验证突变负担假说可以解释选定的绿藻物种线粒体、叶绿体和核基因组的紧密性差异。近年来，绿藻因其在生物技术，特别是可再生能源方面的潜力而引起了人们的兴趣。本文提出的关于这一组的基础工作可以增加它们在实际应用中的价值。

Over the past several decades my laboratory has studied green algae, the group from which land plants arose. The main focus of our work is on organelle genomes, i.e., those in mitochondria and chloroplasts, which are the sites of respiration and photosynthesis, respectively, but we have also been addressing questions related to the nuclear genome (the main genome of the cell), in the study group. The overriding theme of our efforts has been to document and explain the diversity of green algal and sometimes land plant genome features. For the organelle genomes this includes variables like intact vs. fragmented, circular vs. linear, GC-rich vs. AT-rich, compact vs. bloated, and for the nuclear genome, the fraction of its non coding DNA that is of recent plastid and mitochondrial origin. We have also estimated the relative mutation rate and the level of nucleotide diversity at silent (non-coding) sites in the three genetic compartments of green plants (algae and land plants) and used these to explain the variations in genome architecture in members of this group. The proposed work for the next grant period focuses on four main activities: (1) Wider sampling and characterization of the Polytomella clade, a group of green algae that is now colorless and has lost the capacity for photosynthesis and for cell wall synthesis-all currently maintained strains of this important genus come from Europe although North and South American isolates have been described in the past; (2) Evolution of the secondary loss of photosynthesis in Polytomella - much can be learned about essential photosynthetic functions in the model alga Chlamydomonas reinhardtii by comparative plastid proteomics with its close relative Polytomella; (3) Evolution of mitochondrial genome structure in Volvox and Polytomella; and (4) testing the mutational-burden hypothesis as an explanation for the compactness variation in mitochondrial, chloroplast, and nuclear genomes in selected green algal species. In recent years, the green algae have attracted interest because of their potential in biotechnology, particularly, renewable energy. Fundamental work on this group such as proposed here can increase their value in practical applications.