Hwan Su Yoon

The appearance of photosynthetic eukaryotes (algae and plants) dramatically altered the Earth's ecosystem, making possible all vertebrate life on land, including humans. Dating algal origin is, however, frustrated by a meager fossil record. We generated a plastid multi-gene phylogeny with Bayesian inference and then used maximum likelihood molecular clock methods to estimate algal divergence times. The plastid tree was used as a surrogate for algal host evolution because of recent phylogenetic e

The most widely distributed dinoflagellate plastid contains chlorophyll c(2) and peridinin as the major carotenoid. A second plastid type, found in taxa such as Karlodinium micrum and Karenia spp., contains chlorophylls c(1) + c(2) and 19'-hexanoyloxy-fucoxanthin and/or 19'-butanoyloxy-fucoxanthin but lacks peridinin. Because the presence of chlorophylls c(1) + c(2) and fucoxanthin is typical of haptophyte algae, the second plastid type is believed to have originated from a haptophyte tertiary e

Algae include a diverse array of photosynthetic eukaryotes excluding land plants. Explaining the origin of algal plastids continues to be a major challenge in evolutionary biology. Current knowledge suggests that plastid primary endosymbiosis, in which a single-celled protist engulfs and "enslaves" a cyanobacterium, likely occurred once and resulted in the primordial alga. This eukaryote then gave rise through vertical evolution to the red, green, and glaucophyte algae. However, some modern alga

Whole-genome shotgun sequence data from three individual cells isolated from seawater, followed by analysis of ribosomal DNA, indicated that the cells represented three divergent clades of picobiliphytes. In contrast with the recent description of this phylum, we found no evidence of plastid DNA nor of nuclear-encoded plastid-targeted proteins, which suggests that these picobiliphytes are heterotrophs. Genome data from one cell were dominated by sequences from a widespread single-stranded DNA vi

Previous phylogenetic studies of the Rhodophyta have provided a framework for understanding red algal phylogeny, but there still exists the need for a comprehensive analysis using a broad sampling of taxa and sufficient phylogenetic information to clearly define the major lineages. In this study, we determined 48 sequences of the PSI P700 chl a apoprotein A1 ( psa A) and rbc L coding regions and established a robust red algal phylogeny to identify the major clades. The tree included most of the

Dinoflagellates are important aquatic primary producers and cause "red tides." The most widespread plastid (photosynthetic organelle) in these algae contains the unique accessory pigment peridinin. This plastid putatively originated via a red algal secondary endosymbiosis and has some remarkable features, the most notable being a genome that is reduced to 1-3 gene minicircles with about 14 genes (out of an original 130-200) remaining in the organelle and a nuclear-encoded proteobacterial Form II

BACKGROUND: Our understanding of the eukaryotic tree of life and the tremendous diversity of microbial eukaryotes is in flux as additional genes and diverse taxa are sampled for molecular analyses. Despite instability in many analyses, there is an increasing trend to classify eukaryotic diversity into six major supergroups: the 'Amoebozoa', 'Chromalveolata', 'Excavata', 'Opisthokonta', 'Plantae', and 'Rhizaria'. Previous molecular analyses have often suffered from either a broad taxon sampling u

Abstract Phylogenetic comparisons suggest that plastid primary endosymbiosis, in which a single‐celled protist engulfs and ‘enslaves’ a cyanobacterium, likely occurred once and resulted in the primordial alga. This photosynthetic cell diversified, through vertical evolution, into the ubiquitous green (Chlorophyta) and red (Rhodophyta) algae, and the more scarce Glaucophyta. However, some modern algal lineages have a more complicated evolutionary history involving a secondary endosymbiotic event,

Red algae (Rhodophyta) underwent two phases of large-scale genome reduction during their early evolution. The red seaweeds did not attain genome sizes or gene inventories typical of other multicellular eukaryotes. We generated a high-quality 92.1 Mb draft genome assembly from the red seaweed Gracilariopsis chorda, including methylation and small (s)RNA data. We analyzed these and other Archaeplastida genomes to address three questions: 1) What is the role of repeats and transposable elements (TE

BACKGROUND: The red algae (Rhodophyta) diverged from the green algae and plants (Viridiplantae) over one billion years ago within the kingdom Archaeplastida. These photosynthetic lineages provide an ideal model to study plastid genome reduction in deep time. To this end, we assembled a large dataset of the plastid genomes that were available, including 48 from the red algae (17 complete and three partial genomes produced for this analysis) to elucidate the evolutionary history of these organelle