Protein sorting in complex plastids.

Area of Science:

• Cell Biology
• Evolutionary Biology
• Biochemistry

Background:

• Photosynthesis originated in eukaryotes through endosymbiosis with cyanobacteria, forming primary plastids.
• Secondary and tertiary endosymbiosis events have led to the widespread distribution of plastids across diverse eukaryotic lineages.
• Complex plastids, resulting from multiple endosymbioses, are characterized by three or four bounding membranes.

Purpose of the Study:

• To review the mechanisms of protein translocation across the multiple membranes of complex plastids.
• To highlight advances in understanding how nuclear-encoded proteins are imported into the plastid stroma.
• To discuss the significance of gene transfer and protein import in the evolution of plastids.

Main Methods:

• Review of ultrastructural and molecular research over the last two decades.
• Analysis of gene transfer events from endosymbionts to host nuclei.
• Examination of protein import pathways across four membranes.

Main Results:

• Plastids exhibit significant lateral mobility across the eukaryotic tree of life.
• Gene transfer to the host nucleus is a common feature of endosymbiosis, enabling centralized control.
• Understanding protein translocation across four membranes is key to comprehending complex plastid function.

Conclusions:

• The evolution of complex plastids involves intricate protein import pathways essential for their function.
• Studying protein translocation across multiple membranes provides insights into organelle evolution and cellular control.
• This review synthesizes current knowledge on protein import into plastids, particularly within the context of endosymbiosis and organelle biogenesis.