Molecular evolution of green algae

在过去的几十年里，我的实验室一直在研究绿色藻类，这是陆地植物的起源。我们工作的主要重点是细胞器基因组，即，线粒体和叶绿体中的那些，它们分别是呼吸和光合作用的场所，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）有关的问题。我们努力的首要主题是记录和解释绿色藻类的多样性，有时是陆地植物的基因组特征。对于细胞器基因组，这包括变量，如完整与片段化，圆形与线性，富含GC与富含AT，紧凑与膨胀，对于核基因组，其非编码DNA的部分是最近的质体和线粒体起源。我们还估计了相对突变率和水平的核苷酸多样性在沉默（非编码）的位点在三个遗传隔室的绿色植物（藻类和陆地植物），并用这些来解释基因组结构的变化，在这个组的成员。下一个资助期的拟议工作集中在四个主要活动上：（1）对Polytomella进化枝进行更广泛的取样和表征，Polytomella进化枝是一组绿色藻类，现在已经无色，并且已经失去了光合作用和细胞壁合成的能力--尽管过去已经描述了北美和南美的分离株，但目前这一重要属的所有菌株都来自欧洲;（2）Polytomella光合作用次生损失的进化--通过与其近缘种Polytomella的质体蛋白质组学比较，可以了解到模式种莱茵衣藻（Chlamyeliumreinhardtii）光合作用的基本功能;（3）团藻和Polytomella线粒体基因组结构的进化;以及（4）测试突变负担假说作为选择的绿色藻类物种中线粒体、叶绿体和核基因组的紧凑性变化的解释。近年来，绿色藻类由于其在生物技术，特别是可再生能源方面的潜力而引起了人们的兴趣。对这一群体的基础工作，如这里提出的，可以增加其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.