Our Research Topics

Endosymbiosis and plastid evolution

The origin of photosynthetic organelles via endosymbiosis more than 1 Gya ago was a major detonator of eukaryotic diversification.

 

The evolution of a stable endosymbiotic relationship between eukaryotic cells and photosynthetic cyanobacteria involved series of cellular and molecular processes that are not entirely understood. Critical steps toward the evolution of plastids occurred when the host cell gained genetic and metabolic control over the captured cyanobacterium.

Proteins recruited from the host repertoire had major roles initiating the metabolite exchange between both symbiotic partners. Concurrently, the relocation of certain cyanobacterial genes into the host nuclear genome was critical to coordinate the division of the endosymbiotic cells and the transit of nuclear-encoded proteins into the novel organelle.

endosymybiosis and plastids
Key subcellular events involved in the evolution of primary plastids
The genome reduction of the endosymbiotic cyanobacteria (Or) was triggered by both gene losses via deleterious events and endosymbiotic gene transfer (EGT) into the host nucleus (Nu).
The evolution of Metabolic Interdependencies and Protein Import Systems were likely part of the initial steps of the endosymbiotic association.
Archaeplastida

The Archaeplastida hypothesis.

The common origin of the Archaeplastida is a widely accepted idea but there are considerable contradictory phylogenetic results that require further investigation.

Considerable cellular and genomic evidence suggest that the Archaeplastida supergroup, which includes Glaucophyta, Rhodophyta (red algae) and Viridiplantae (green algae and land plants), descended from common ancestors that recruited endosymbiotic cyanobacteria as organelles (i.e., primary plastids) more than a billion years in the past.

 

Testing the common origin of the Archaeplastida  is essential to elucidate and understand the emergence of the first photosynthetic eukaryotes.

 

One avenue to study this hypothesis is through comparative studies of the genomic and protein repertoires from the different Archaeplastida lineages. Green algae and land plants have been thoroughly studied in this respect, but this is not the case for glaucophytes.

References

  • Reyes-Prieto A, Hackett JD, Soares MB, Bonaldo MF, Bhattacharya D. Current Biology. 2006. 16: 2320-2325.

  • Reyes-Prieto A, Bhattacharya D. Molecular Phylogenetics and Evolution. 2007. 45: 384-391.

  • Moustafa A, Reyes-Prieto A, Bhattacharya D. PLoS ONE. 2008 3: e2205.

  • Reyes-Prieto A, Yoon HS, Moustafa A, Yang EC, Andersen RA, Boo SM, Nakayama T, Ishida K, Bhattacharya D. Molecular Biology and Evolution. 2010. 27:1530-1537.

  • Chan CX, Bhattacharya D and Reyes-Prieto A. Mobile Genetic Elements. 2012. 2(2).

  • Reyes-Prieto A, Moustafa A. Scientific Reports2012. 2:955.

  • Slamovits C and Reyes-Prieto A. 2013. Lateral gene transfer and the evolution of photosynthesis in eukaryotes. In , Lateral Gene Transfer in Evolution SE - 2 (pp. 15–53). Springer, New York, USA. U. Gophna Editor.

  • Reyes-Prieto A. Frontiers in Ecology and Evolution. 2015. 3:100.

Glaucophyte algae:  The blue-green plants 
Glaucophyta is one of the three major lineages of photosynthetic eukaryotes united in the presumed monophyletic supergroup Archaeplastida.
 
Glaucophyta is a fundamental lineage to investigate both the origin of primary plastids and the evolution of algae and plants.
The plastids of glaucophytes possess exceptional characteristics retained from their cyanobacterial ancestor: phycobilisome antennas, a vestigial peptidoglycan wall, and carboxysome-like bodies.
 
These latter two traits are unique among the Archaeplastida and have been suggested as evidence that the glaucophytes diverged earliest during the diversification of this supergroup.
The bule-green plants
The characteristic  coloration is given by the presence of chlorophyll a and the blue phycobiliproteins allophycocyanin and c-phycocyanin in the glaucophyte plastids, called as well cyanelles. The micrograph shows four Gloeochaete wittrockiana cells with concetric blue-green cyanelles.
Our research on comprises diverse aspects of the Glaucophyta biology: 
Looking for new glaucophyte species using traditional techniques, FACS flow cytometry and environmental genomics.
We are investigating species distribution, diversity and relationships between different glaucophyte genera to establish the basis for further studies of the ecological diversity of the group.
We use as well comparative genomics to better understand the evolution of this rare group of algae and the origin of Archaplastida
cyanelle
Carboxysome-like bodies (Cbl)
The regular  accumulation of Rubisco in glaucophyte plastids resembles cyanobacterial carboxysomes (Cbl). The Cyanoptyche gloeocystis transmission electron micrography shows as well the thylakoid membranes  (Thy). 
glaucophyta genomes
Comparative genomics
The mitochondrial genomes of Gloeochaete wittrockiana and Cyanoptyche gloeocystis were recently report by our group. The phylogenetic analyses of 14 mitochondrial genes from representative taxa from the major eukaryotic supergroups recover a clade uniting the three Archaeplastida lineages

References

  • Jackson CJ, Clayden S, Reyes-Prieto A. Acta Societatis Botanicorum Poloniae. 2015. 84: 149-165

  • Jackson CJ, Reyes-Prieto A. Genome Biology and Evolution. 2014. 6:2774-2785.

  • Smith DR, Jackson C and Reyes-Prieto A. Molecular Phylogenetics and Evolution. 2014. 79:380-384.

  • Chong J, Jackson C, Kim JI, Yoon HS, Reyes-Prieto A. Molecular Phylogenetics and Evolution. 2014. 76C:181-188.

The loss of photosynthesis

The autotrophic abilities bestowed by plastids are responsible for much of the eukaryotic diversity we observe today. Howver, the presence of numerous plastid-harbouring nonphotosynthetic groups demonstrates that photosynthesis is dispensable under certain ecological conditions and that the loss of photosynthesis is not uncommon among mixotrophic alga.

loss of photosynthesis
Photosynthesis is dispensable in mixotrophic algae
colorless chlamydomonadaceae
Photosynthesis has been lost three times in Chlamydomonadacea

The loss of photosynthesis has occurred at least three independent times in the green algal Order Chlamydomonadales. The colorless cases are represented by diverse species of the genera  Polytoma and  Polytomella

Polytoma and Polytomella are particularly interesting because , in contrast to the well-known parasitic and pathigenic colorless species such as Helicosporidium and Protoheca, they evolved towards non-photosynthetic life styles as free-living organisms.

These colorless algae represent exceptional  lineages for investigating the genomic consequences of the loss of photosynthesis in free-living algae without the confounding effects associated with adopting a parasitic/pathogenic lifestyle.

References

  • Figueroa-Martinez F, Nedelcu AM, Smith DR, Reyes-Prieto A. New Phytologist. 2015. 206:972–982.

  • Del Vasto M, Figueroa-Martinez F, Featherston J, González MA, Reyes-Prieto A, Durand PM, Smith DR. Genome Biology and Evolution. 2015. 7:656-663.

  • Reyes-Prieto A, El-Hafidi M, Moreno-Sánchez R, González-Halphen D. Biochimica et Biophysica Acta. 2002. 1554: 170-179.

Acknowledgments

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© 2016 by Adrian Reyes Prieto.
 

Phylogenetic analysis of Chlamydomonadaceae plastid 16S rRNA