Understanding the rules of life

Bioscience for sustainable agriculture and food

Bioscience for renewable resources and clean growth

Category: Standard Studentships

Illuminating chloroplast origin and function through a discovery of novel protein transport route

Project No.2257

Primary Supervisor

Associate Prof Ivo Tews  – University of Southampton


Dr Anastasios Tsaousis  – University of Kent

Dr Jan Janouškovec – University of Southampton


The major protein transport routes into mitochondria and chloroplasts are thought to be well understood. 

However, new discoveries challenge current textbook models. We have recently discovered a novel protein translocator in red algae. The so far unannotated gene, which encodes for a membrane OMP85 family protein, is encoded directly in the chloroplast genome.  

The aims are of the project are to investigate whether the new translocator can transport protein substrates into the chloroplast and whether its substrate-recognition domain is oriented outwards from the embedding membrane as in plant chloroplasts or inwards as in cyanobacteria. To ascertain the directionality and function of the translocator, a three-pronged approach will be used, which combines evolutionary studies (bioinformatics), cell biology and biochemistry, as well as structural biology techniques contributed by the three host laboratories / PIs. You will use: 

  • microscopy and molecular cell biology to localise the translocator in the chloroplast membrane, determine its orientation by immunolabeling, and test its functionality by conditional gene knockout in the model algal species Porphyridium purpureum; 
  • biochemistry and crystallography to study the 3D structure of the membrane translocator and understand the mechanics of protein transport through studying its cargo recognition POTRA domains;  
  • bioinformatics to determine the distribution and phylogeny of the translocon to update existing models on how chloroplasts have become integrated into eukaryotic cells. 

Study of translocon substrates and expression patterns describe the translocon function and its phylogenetic distribution and allow gaining insights into the origin and evolution of the chloroplast organelle. The findings will reshape our views on how plants and algae became photosynthetic and underwent massive reduction in their chloroplast genomes by acquiring the ability to translocate proteins.