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，陆地植物就是从绿藻中生长出来的。我们的工作主要集中在细胞器基因组上，即线粒体和叶绿体中的基因组，它们分别是呼吸作用和光合作用的位置，但在研究组中，我们也一直在解决与核基因组(细胞的主要基因组)相关的问题。我们努力的压倒一切的主题是记录和解释绿藻的多样性，有时还解释陆地植物的基因组特征。对于细胞器基因组，这包括诸如完整与碎裂、环状与线形、富含GC与富含AT、紧凑与膨胀等变量；对于核基因组，这包括其非编码DNA的一部分，即最近起源于质体和线粒体的部分。我们还估计了绿色植物(藻类和陆地植物)三个遗传间隔中沉默(非编码)位置的相对突变率和核苷酸多样性水平，并用这些来解释这一组成员的基因组结构的差异。下一个资助期的拟议工作集中于四个主要活动：(1)更广泛的采样和表征多毛藻分支，这是一组绿藻，现在是无色的，已经失去了光合作用和细胞壁合成的能力--这个重要属的所有目前保存的菌株都来自欧洲，尽管过去已经描述了北美和南美洲的分离株；(2)多毛藻的次生光合作用丧失的进化--可以通过比较叶绿体蛋白质组学和其近缘多毛藻来了解模式藻衣藻的基本光合作用功能；(3)多毛藻和多毛藻线粒体基因组结构的进化；以及(4)检验突变负担假说，以此来解释部分绿藻物种线粒体、叶绿体和核基因组的紧凑性变化。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。关于这一组的基础工作，如这里提出的，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.