The YlmG protein has a conserved function related to the distribution of nucleoids in chloroplasts and cyanobacteria

Abstract

BackgroundReminiscent of their free-living cyanobacterial ancestor, chloroplasts proliferate by division coupled with the partition of nucleoids (DNA-protein complexes). Division of the chloroplast envelope membrane is performed by constriction of the ring structures at the division site. During division, nucleoids also change their shape and are distributed essentially equally to the daughter chloroplasts. Although several components of the envelope division machinery have been identified and characterized, little is known about the molecular components/mechanisms underlying the change of the nucleoid structure.ResultsIn order to identify new factors that are involved in the chloroplast division, we isolated Arabidopsis thaliana chloroplast division mutants from a pool of random cDNA-overexpressed lines. We found that the overexpression of a previously uncharacterized gene (AtYLMG1-1) of cyanobacterial origin results in the formation of an irregular network of chloroplast nucleoids, along with a defect in chloroplast division. In contrast, knockdown of AtYLMG1-1 resulted in a concentration of the nucleoids into a few large structures, but did not affect chloroplast division. Immunofluorescence microscopy showed that AtYLMG1-1 localizes in small puncta on thylakoid membranes, to which a subset of nucleoids colocalize. In addition, in the cyanobacterium Synechococcus elongates, overexpression and deletion of ylmG also displayed defects in nucleoid structure and cell division.ConclusionsThese results suggest that the proper distribution of nucleoids requires the YlmG protein, and the mechanism is conserved between cyanobacteria and chloroplasts. Given that ylmG exists in a cell division gene cluster downstream of ftsZ in gram-positive bacteria and that ylmG overexpression impaired the chloroplast division, the nucleoid partitioning by YlmG might be related to chloroplast and cyanobacterial division processes.

Isolation, Purification and Characterization of Nucleoids from <i>Synechococcus elongatus</i> PCC 7942

“…However, during purification, a huge amount of genomic DNA was released together with the thylakoid membranes (data not shown). Therefore, we conclude that the thylakoid membrane is a part of se-nucleoid, because se-genomic DNA is tightly associated with thylakoid membranes as suggested previously [48]- [50].…”

Modified Clp Protease Complex in the ClpP3 Null Mutant and Consequences for Chloroplast Development and Function in Arabidopsis

“…Finally, a DEAD box DNA helicase likely involved in DNA folding and YMLG1 were up-regulated. YMLG1 (Kabeya et al, 2010) is involved in the distribution of nucleoids in chloroplast. Together, these results suggest that the loss of Clp protease function has an impact on the plastid chromosome.…”

Dual targeting of a mature plastoglobulin/fibrillin fusion protein to chloroplast plastoglobules and thylakoids in transplastomic tobacco plants

“…After blocking with 3 % skim milk in PBS for 30 min, the samples were incubated for 16 h at 4°C with the anti-streptavidin antibody with StrepMAB-Immo Oyster 488 diluted 1:200. Chloroplasts were then washed twice with 3 % skim milk in PBS and then once with PBS buffer (Kabeya et al 2010). Fluorescence was detected using the FITC (488 nm) laser line from a LEICA TSC SP5 microscope (LEICA Microsystems).…”