Genes Sufficient for Synthesizing Peptidoglycan are Retained in Gymnosperm Genomes, and MurE from Larix gmelinii can Rescue the Albino Phenotype of Arabidopsis MurE Mutation.
The endosymbiotic theory states that plastids are derived from a single cyanobacterial ancestor that possessed a cell wall. Peptidoglycan (PG), the main component of the bacteria cell wall, gradually degraded during plastid evolution. PG-synthesizing Mur genes have been found to be retained in the genomes of basal streptophyte plants, although many of them have been lost from the genomes of angiosperms. The enzyme encoded by bacterial MurE genes catalyzes the formation of the UDP-N-acetylmuramic acid (UDP-MurNAc) tripeptide in bacterial PG biosynthesis. Knockout of the MurE gene in the moss Physcomitrella patens resulted in defects of chloroplast division, whereas T-DNA-tagged mutants of Arabidopsis thaliana for MurE revealed inhibition of chloroplast development but not of plastid division, suggesting that AtMurE is functionally divergent from the bacterial and moss MurE proteins. Here, we could identify 10 homologs of bacterial Mur genes, including MurE, in the recently sequenced genomes of Picea abies and Pinus taeda, suggesting the retention of the plastid PG system in gymnosperms. To investigate the function of gymnosperm MurE, we isolated an ortholog of MurE from the larch, Larix gmelinii (LgMurE) and confirmed its presence as a single copy per genome, as well as its abundant expression in the leaves of larch seedlings. Analysis with a fusion protein combining green fluorescent protein and LgMurE suggested that it localizes in chloroplasts. Cross-species complementation assay with MurE mutants of A. thaliana and P. patens showed that the expression of LgMurE cDNA completely rescued the albefaction defects in A. thaliana but did not rescue the macrochloroplast phenotype in P. patens. The evolution of plastid PG and the mechanism behind the functional divergence of MurE genes are discussed in the context of information about plant genomes at different evolutionary stages.
College of Life Sciences, Inner Mongolia University, Hohhot 010021, China.
Xiaofei
X
Lin
College of Life Sciences, Inner Mongolia University, Hohhot 010021, China.
Ningning
N
Li
Graduate School of Science and Technology, Kumamoto University, Kumamoto, 860-8555 Japan.
Hiromi
H
Kudo
College of Biological Science, China Agriculture University, Beijing, 100083, China.
Zhe
Z
Zhang
College of Life Sciences, Inner Mongolia University, Hohhot 010021, China.
Jinyu
J
Li
College of Life Sciences, Inner Mongolia University, Hohhot 010021, China.
Li
L
Wang
College of Forestry, Inner Mongolia Agricultural University, Hohhot 010019, China.
Wenbo
W
Zhang
Faculty of Advanced Science and Technology, Kumamoto University, Kumamoto, 860-8555 Japan.
Katsuaki
K
Takechi
Faculty of Advanced Science and Technology, Kumamoto University, Kumamoto, 860-8555 Japan.|Institute of Pulsed Power Science, Kumamoto University, Kumamoto, 860-8555 Japan.
Hiroyoshi
H
Takano
D017360:Arabidopsis / Q000201:enzymology / Q000235:genetics* / Q000378:metabolism; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism; D001426:Bacterial Proteins / Q000235:genetics; D019068:Bryopsida / Q000235:genetics / Q000378:metabolism; D002473:Cell Wall / Q000235:genetics / Q000378:metabolism; D002736:Chloroplasts / Q000235:genetics / Q000378:metabolism; D000458:Cyanobacteria / Q000235:genetics / Q000378:metabolism; D032462:Cycadopsida / Q000235:genetics* / Q000378:metabolism; D004269:DNA, Bacterial; D018506:Gene Expression Regulation, Plant; D055786:Gene Knockout Techniques; D005798:Genes, Bacterial; D017343:Genes, Plant; D018745:Genome, Plant; D049452:Green Fluorescent Proteins; D028221:Larix / Q000235:genetics* / Q000378:metabolism; D019684:Magnoliopsida / Q000235:genetics; D009154:Mutation; D046915:Penicillin-Binding Proteins / Q000235:genetics* / Q000378:metabolism; D010457:Peptidoglycan / Q000235:genetics* / Q000378:metabolism; D010641:Phenotype; D028222:Picea / Q000235:genetics; D041603:Pinus taeda / Q000235:genetics; D018515:Plant Leaves / Q000235:genetics; D010940:Plant Proteins / Q000235:genetics* / Q000378:metabolism; D018087:Plastids / Q000235:genetics / Q000378:metabolism; D012639:Seeds / Q000235:genetics / Q000378:metabolism
D029681:Arabidopsis Proteins; D001426:Bacterial Proteins; D004269:DNA, Bacterial; D046915:Penicillin-Binding Proteins; D010457:Peptidoglycan; D010940:Plant Proteins; C036483:T-DNA; D049452:Green Fluorescent Proteins
Chloroplast; Evolution; Gymnosperm; Larix gmelinii; MurE; Plastid peptidoglycan