Chloroplast division and peptidoglycan walls in streptophytes

Abstract

The acquisition of chloroplasts was an important event in the evolution of plant cells. It is widely accepted that plastids (chloroplasts) evolved from engulfed endosymbiotic cyanobacteria. The plastids of green plants are thought to have lost their ability to produce peptidoglycan during evolution. However, we found that the moss Physcomitrella (Physcomitrium patens) possesses 11 genes required to generate peptidoglycan in plastids, and that single-gene knockouts of these genes trigger defects in chloroplast division. Moreover, we used a click chemistry-based metabolic labelling method to target peptidoglycan, and found that peptidoglycan surrounded the chloroplasts of P. patens. Recent results suggest that the chloroplasts of several streptophytes have a peptidoglycan wall. The evolution of chloroplasts with peptidoglycan walls is discussed.