Hypothesis for the evolution of three-helix Chl a/b and Chl a/c light-harvesting antenna proteins from two-helix and four-helix ancestors

The nuclear-encoded Chl a/b and Chl a/c antenna proteins of photosynthetic eukaryotes are part of an extended family of proteins that also includes the early light-induced proteins (ELIPs) and the 22 kDa intrinsic protein of PS II (encoded by psb S gene). All members of this family have three transmembrane helices except for the psb S protein, which has four. The amino acid sequences of these proteins are compared and related to the three-dimensional structure of pea LHC II Type I (Kühlbrandt and Wang, Nature 350: 130–134, 1991). The similarity of psb S to the three-helix members of the family suggests that the latter arose from a four-helix ancestor that lost its C-terminal helix by deletion. Strong internal similarity between the two halves of the psb S protein suggests that it in turn arose as the result of the duplication of a gene encoding a two-helix protein. Since psb S is reported to be present in at least one cyanobacterium, the ancestral four-helix protein may have been present prior to the endosymbiotic event or events that gave rise to the photosynthetic eukaryotes. The Chl a/b and Chl a/c antenna proteins, and the immunologically-related proteins in the rhodophytes may have had a common ancestor which was present in the early photosynthetic eukaryotes, and predated their division into rhodophyte, chromophyte and chlorophyte lineages. The LHC I-LHC II divergence probably occurred before the separation of higher plants from chlorophyte algae and euglenophytes, and the different Types of LHC I and LHC II proteins arose prior to the separation of angiosperms and gymnosperms.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/43538/1/11120_2004_Article_BF00029382.pd

Biodiesel from aquatic species. Project report: FY 1993

Researchers in the Biodiesel/Aquatic Species Project focus on the use of microalgae as a feedstock for producing renewable, high-energy liquid fuels. The program`s basic premise is that microalgae, which have been called the most productive biochemical factories in the world, can produce up to 30 times more oil per unit of growth area than land plants. It is estimated that 150 to 400 barrels of oil per acre per year (0.06 to 0.16 million liters/hectar) could be produced with microalgal oil technology. Initial commercialization of this technology is envisioned for the desert Southwest because this area provides high solar radiation and offers flat land that has few competing uses (hence low land costs). Similarly, there are large saline aquifers with few competing uses in the region. This water source could provide a suitable, low-cost medium for the growth of many microalgae. The primary area of research during FY 1993 was the effort to genetically improve microalgae in order to control the timing and magnitude of lipid accumulation. Increased lipid content will have a direct effect on fuel price, and the control of lipid content is a major project goal. The paper describes progress on the following: culture collection; molecular biology of lipid biosynthesis; microalgal transformation; and environmental, safety, and health and quality assurance