Machida Mariko, Takechi Katsuaki, Sato Hiroshi, Chung Sung Jin, Kuroiwa Haruko, Takio Susumu, Seki Motoaki, Shinozaki Kazuo, Fujita Tomomichi, Hasebe Mitsuyasu, Takano Hiroyoshi
Graduate School of Science and Technology, Kumamoto University, Kumamoto 860-8555, Japan.
Proc Natl Acad Sci U S A. 2006 Apr 25;103(17):6753-8. doi: 10.1073/pnas.0510693103. Epub 2006 Apr 17.
The general consensus is that a cyanobacterium phagocytosed by a host cell evolved into the plastids of red and green algae, land plants, and glaucophytes. In contrast to the plastids of glaucophytes, which retain a cyanobacterial-type peptidoglycan layer, no wall-like structures have been detected in plastids from other sources. Although the genome of Arabidopsis thaliana contains five genes that are essential for peptidoglycan synthesis, MurE, MurG, two genes for D-Ala-D-Ala ligase (Ddl), and the gene for translocase I (MraY), their functions have not been determined. We report that the moss Physcomitrella patens has nine homologous genes related to peptidoglycan biosynthesis: MurA, B, C, D, E, and F, Ddl, genes for the penicillin-binding protein Pbp, and dd-carboxypeptidase (Dac). Corroborating a computer prediction, analysis of the GFP fusion proteins with the N terminus of PpMurE or of PpPbp suggests that these proteins are located in the chloroplasts. Gene disruption of the PpMurE gene in P. patens resulted in the appearance of macrochloroplasts both in protonema and in leaf cells. Moreover, gene knockout of the P. patens Pbp gene showed inhibition of chloroplast division in this moss; however, no Pbp gene was found in A. thaliana.
普遍的共识是，被宿主细胞吞噬的蓝细菌进化成了红藻、绿藻、陆地植物和灰胞藻的质体。与保留蓝细菌型肽聚糖层的灰胞藻质体不同，在其他来源的质体中未检测到类似壁的结构。尽管拟南芥的基因组包含五个对肽聚糖合成至关重要的基因，即MurE、MurG、两个D - Ala - D - Ala连接酶（Ddl）基因和转位酶I（MraY）基因，但其功能尚未确定。我们报道，小立碗藓有九个与肽聚糖生物合成相关的同源基因：MurA、B、C、D、E和F、Ddl、青霉素结合蛋白Pbp基因和D - 羧肽酶（Dac）。对带有PpMurE或PpPbp N端的绿色荧光蛋白融合蛋白的分析证实了计算机预测，表明这些蛋白位于叶绿体中。小立碗藓中PpMurE基因的基因破坏导致原丝体和叶细胞中出现大叶绿体。此外，小立碗藓Pbp基因的基因敲除显示该苔藓的叶绿体分裂受到抑制；然而，在拟南芥中未发现Pbp基因。
