Figure 1.

Schematic view of the cyanobacterial and chloroplast division complexes and distribution of the chloroplast division proteins of cyanobacterial origin. (A) Schematic comparison of the division complex among cyanobacteria, along with the chloroplasts of glaucophytes and those in other lineages. Glaucophyte chloroplasts have a PG between the inner- and the outer-envelope membrane, as do cyanobacteria. To allow the outer envelope membrane constrict, the PG layer at the division site has to be cut from the outermost site (a process called PG splitting), as in bacterial cell division. CM, cytoplasmic membrane; IE, inner envelope membrane; OE, outer envelope membrane; OM, outer membrane; PG, peptidoglycan layer. (B) Domain organization of DipM/NlpD, EnvC, LytE and PG amidases (Ami) which are involved in PG splitting in bacteria. DipM/NlpD and LytE usually contain three to five repeats of the LysM motif, but only one LysM motif is shown. The N-terminal LysM, coiled-coil or Amin domain targets the protein to the septum and the C-terminal LytM/M23, NlpC/P60 or Amidase 3 domain has a hydrolase activity. (C) Distribution of the chloroplast division proteins of cyanobacterial origin (updated from [32]). A certain lineages of photosynthetic eukaryotes possess DipM homologs probably descended from a cyanobacterial ancestor of chloroplasts. The branch lengths do not represent the phylogenetic distance. The red cross marks on the nodes indicate the deduced timing of loss of DipM. The GenBank accession numbers of the amino acid sequences are summarized in Additional file 1: Table S1. EnvC was found in some of the cyanobacterial species (e.g. GI:427708140 in Nostoc sp. PCC 7107), but not in S. elongatus. The data on the charophytes are not based on a single species but a combination of species.