Mapping the pathway for protein secretion in the secondary endosymbiotic alga Nannochloropsis oceanica

This study presents the identification of signal peptides that direct protein secretion in the seawater microalga Nannochloropsis oceanica, with an efficiency that is highly sensitive to environmental parameters such as light and CO2 availability. This enabled to reconstruct the pathway for protein secretion in this organism. Proteins channelled for export are in fact first targeted to the periplastidial compartment, an exclusive structure of secondary endosymbiotic algae, that act as hub for protein trafficking. Subsequently, proteins are directed through the endoplasmic reticulum into the periplasmic space between the cell membrane and the cell wall, from where they are released upon cell division.