Genome of the red alga Porphyridium purpureum

The limited knowledge we have about red algal genomes comes from the highly specialized extremophiles, Cyanidiophyceae. Here, we describe the first genome sequence from a mesophilic, unicellular red alga, Porphyridium purpureum. The 8,355 predicted genes in P. purpureum, hundreds of which are likely to be implicated in a history of horizontal gene transfer, reside in a genome of 19.7 Mbp with 235 spliceosomal introns. Analysis of light-harvesting complex proteins reveals a nuclear-encoded phycobiliprotein in the alga. We uncover a complex set of carbohydrate-active enzymes, identify the genes required for the methylerythritol phosphate pathway of isoprenoid biosynthesis, and find evidence of sexual reproduction. Analysis of the compact, function-rich genome of P. purpureum suggests that ancestral lineages of red algae acted as mediators of horizontal gene transfer between prokaryotes and photosynthetic eukaryotes, thereby significantly enriching genomes across the tree of photosynthetic life

Gene Transfer from Bacteria and Archaea Facilitated Evolution of an Extremophilic Eukaryote

Schoenknecht G, Chen W-H, Ternes CM, et al. Gene Transfer from Bacteria and Archaea Facilitated Evolution of an Extremophilic Eukaryote. Science. 2013;339(6124):1207-1210.Some microbial eukaryotes, such as the extremophilic red alga Galdieria sulphuraria, live in hot, toxic metal-rich, acidic environments. To elucidate the underlying molecular mechanisms of adaptation, we sequenced the 13.7-megabase genome of G. sulphuraria. This alga shows an enormous metabolic flexibility, growing either photoautotrophically or heterotrophically on more than 50 carbon sources. Environmental adaptation seems to have been facilitated by horizontal gene transfer from various bacteria and archaea, often followed by gene family expansion. At least 5% of protein-coding genes of G. sulphuraria were probably acquired horizontally. These proteins are involved in ecologically important processes ranging from heavy-metal detoxification to glycerol uptake and metabolism. Thus, our findings show that a pan-domain gene pool has facilitated environmental adaptation in this unicellular eukaryote

Cation channels by subunit III of the channel portion of the chloroplast H+-ATPase

AbstractThe chloroplast H+-ATPase (CF0CF1) was isolated and reconstituted into lipid vesicles by dialysis technique. Vesicles were fused by dehydration/ rehydration to obtain cell-size liposomes, which were studied by patch-clamp techniques. Single-channel activity was observed with several conductance levels in the range of some 10 pS (100 mM KCl). In contrast to intact CF0, which conducts protons, only (even at pH 8), these channels were permeable for potassium and sodium. Venturicidin, which blocks proton flow through intact CF0, here greatly decreased the single-channel open probability. Subunit III of CF0, alone, yielded cation channels resembling the former. Our tentative interpretation is, that dearrangement or fragmentation of CF0 caused the potassium and sodium permeability, which, however, is suppressed in intact CF0