ARC3, a Chloroplast Division Factor, is a Chimera of Prokaryotic FtsZ and Part of Eukaryotic Phosphatidylinositol-4-phosphate 5-kinase

Abstract

The arc3 (accumulation and replication of chloroplast) mutant of Arabidopsis thaliana has a small number of abnormally large chloroplasts in the cell, suggesting that chloroplast division is arrested in the mutant and ARC3 has an important role in the initiation of chloroplast division. To elucidate the role of ARC3, first we identified the ARC3 gene, and determined the location of ARC3 protein during chloroplast division because the localization and spatial orientation of such division factors are vital for correct chloroplast division. Sequencing analysis showed that ARC3 was a fusion of the prokaryotic FtsZ and part of the eukaryotic phosphatidylinositol-4-phosphate 5-kinase (PIP5K) genes. The PIP5K-homologous region of ARC3 had no catalytic domain but a membrane-occupation-and-recognition-nexus (MORN) repeat motif. Immunofluorescence microscopy, Western blotting analysis and in vitro chloroplast import and protease protection assays revealed that ARC3 protein was soluble, and located on the outer surface of the chloroplast in a ring-like structure at the early stage of chloroplast division. Prokaryotes have one FtsZ as a gene for division but have no ARC3 counterparts, the chimera of FtsZ and PIP5K, suggesting that the ARC3 gene might have been generated from FtsZ as another division factor during the evolution of chloroplast by endosymbiosis.

Unfolding the secrets of coral–algal symbiosis

“…Proteins containing MORN repeats could be involved in cell division, as in the parasite Toxoplasma gondii, where they are located in the cell division apparatus and are proposed to play a role in the cytoskeleton interaction between the parasite and host (Gubbels et al, 2006;Takeshima et al, 2000). In plants, the MORN repeat motif has been discovered in the ARC3 gene that is important for the replication of chloroplasts (Shimada et al, 2004). In addition, the symbiotic interaction and signaling between legumes and rhizobacteria is mediated via phosphatidylinositide-regulated endocytosis (Peleg-Grossman et al, 2007), whereas glycosylphosphatidylinositol is important for the cell recognition and detection of microbes by the host (Davy et al, 2012).…”

CDP1, a novel component of chloroplast division site positioning system in Arabidopsis

“…Although a dozen of Arabidopsis arc mutants relevant to the chloroplast division process have been reported many years ago [35,36], only a few of them are cloned by map-based cloning during a long period of time [22,23,[37][38][39]. Mapping genes for these mutants is laborious, because one has to use microscope for phenotyping [22,38].…”

“…Mutation of ARC3 causes a phenotype of misplacement of chloroplast division site, similar to that of minD mutant or MinE-overexpressing transgenic plants [22,[25][26][27]. So far, the homolog of MinC is still missing in higher plants.…”

“…Many proteins involved in chloroplast division are homologs of bacterial cell di-CDP1, component of chloroplast division site positioning system 878 npg vision proteins, including FtsZ family, MinD, MinE and ARC6 [6,9,20,21]. FtsZ family of proteins in Arabidopsis includes FtsZ1, FtsZ2 subfamily and ARC3 [20,22]. They are all important for chloroplast division, but with distinct roles.…”

Arabidopsis Cotyledon-Specific Chloroplast Biogenesis Factor CYO1 Is a Protein Disulfide Isomerase

“…The sequences of the amplified fragments were confirmed. Expression and purification were performed as described previously (Shimada et al, 2004). E. coli strain BL21(DE3) was used for the expression of recombinant fusion proteins bearing a 6xHis tag.…”