Euk Literature Data and Info

Estimations for HGT

Movement from organelle to nucleus:
Avoid mutational effects of oxygen free radicals (Allen & Raven, 1996, JME 42:482-492)
Avoid effects of Muller's ratchet in non-recombining genomes (Martin and Herrmann, 1998, Plant Physiol 118:9-17)
Selective pressure to attain small size to increase replicative speed and metabolic efficiency (Selosse et al 2001, T Ecol and Evol 16:135-141)
Plastid genome reduction with loss of photosynthetic ability: Plasmodium falciparium, Epifagus virginalis, Euglena longa

Why do plastid genomes resist transfer:
Some gene products may be toxic to the cell;
Too hydropholic to be transported through cytosol or plastid membrane (15)
Core photosytemt proteins are under tight regulation to maintain the redox potiential to maintain efficiency and prevent oxygen free radicals, (Selosse et al)

Secondary emdosymbiosis of red algal gave rise to major protist assemblage- chromalveolates: Fast et al 2001, Yoon et al 2002, Nozaki et al 2003

Dinoflagellates (Alveolates)

Dinoflagellate algae are unparalleled in their ability to capture photosynthetic organelles through endosymbiosis. Their plastid genome contains single-gene minicircles which encode an incomplete set of plastid proteins (~15). ESTs from Alexandria tamarense identify 48 photosynthetic genes in the nuclear genome. 15 of these genes are always found on the plastid genome of other algae and plants but have been transferred into this dinoflagellate. The plastid-targeted genes have red and green algal origins.

The dinoflagellates encode the smallest number of plastid genes of any photosynthetic eukaryote. The single DNA-circle configuration of the plastid genome in apicomplexans, which contrasts with the unique minicircle plastid genes in peridinin dinoflagellates and the nuclear location of tufA in A. tamarense, suggests that extensive plastid gene transfer in dinoflagellates probably occurred independently after their split from apicomplexans. The extreme genome reduction evident in apicoplasts surely results from the evolution of an intracellular lifestyle with the loss of genes no longer needed for photosynthesis (e.g., as in the nonphotosynthetic parasitic plant Epifagus[29]). This type of reduction appears, however, to be quite different from that in dinoflagellates, many of which are photosynthetic and have for unknown reasons transformed the plastid genome required for this function into minicircles and undergone wholesale photosynthetic gene transfer to the nucleus.

Hackett et al, 2004 Current Biology 14:213-218

Dinos have been stealing genes through history. 2 separate plastid transpormations in Dino (Bhattacharya) Dino mini circles may be the minimal gene set for a plastid.

Alexandria tamaranse has over 200,000 Mg on 122 chromosomes, may use proteobacter LLP-bact-histones to package DNA (Wong et al 2003)

 

Plastid genomes are typically AT rich
Dinoflagellate minicircles are typically about 4 kilobases (Zhang et al 1999, Nature 400:155-159
48 nuclear encoded in A.tamarense G+C is 61.&%;
2nd and 3rd position codon are 34.8% and 77.4%

Genes typicallay found on minicircles: atpA, atpB, petB, petD, psaA, psaB, psbA-E, ycf16, ycf24, rpl28, rpl23, 16S and 23S rRNA, and non-coding circles

Psudogenes have been found on minicircles,16s, 23S, psbA, psbC, Zhang et al, 2001 MBE 19:1558-1565

Diatoms (Stramenophytes)

Ecology - in oceans 80% are phototrophic picoplankton, 20% are heterotrophs - Massona, Ventner SARS 11 are mostly <0.8, Copy # of rRNA in euks can range forom 1 - 10,000 (prok 1- 13).