Poster: Organelle Biogenesis

Abs # 1159: Relationship between bacterial peptidoglycan synthesis pathway and chloroplast biogenesis

Presenter:	Takano, Hiroyoshi , takano@kumamoto-u.ac.jp
Authors	Takano, Hiroyoshi  (A)   Machida, Mariko  (A)   Katayama, Nami  (A)   Izumi, Yoshihiro  (B)   Takio, Susumu  (C)   Fujita, Tomomichi  (D)   Hasebe, Mitsuyasu  (D)
Affiliations:	(A): Graduate School of Science and Technology, Kumamoto University, Japan (B): Faculty of Education and Welfare Science, Oita University, Japan (C): Center for Marine Environment Studies, Kumamoto University, Japan (D): National Institute for Basic Biology, Japan
Web Site:	http://www.sci.kumamoto-u.ac.jp/bio.iden/takano/english.html

The endosymbiotic theory states that all chloroplasts are derived from a single cyanobacterial ancestor. It is widely agreed that the chloroplasts of red algae and higher plants have no peptidoglycan layer. Therefore, the evolution from endocytobiont into a wall-less, photosynthetic organelle involved a reduction in and loss of the cyanobacterial cell wall. In the moss Physcomitrella patens, treatment with ampicillin, b-lactam antibiotic, which binds penicillin-binding proteins to inhibit peptidoglycan synthesis, resulted in a few giant chloroplasts per cell. Treatment with ampicillin also led to a decrease in the number of chloroplasts in the mosses Funaria hygrometrica and Polytrichum commune. Moreover, ampicillin caused the appearance of macrochloroplasts in the liverwort Marchantia polymorpha and the pteridophyte Selaginella nipponica. On the other hand, b-lactams do not appear to affect chloroplast morphology in seed plants. Antibiotics that inhibit bacterial peptidoglycan synthesis at positions different from b-lactams also affected the size and number of chloroplasts per cell in P. patens. D-cycloserine caused a rapid decrease in chloroplast number and its effect was similar to that of b-lactam antibiotics. Fosfomycin affected half of the cells, while vancomycin affected a few cells. These findings suggest that genes derived from the bacterial peptidoglycan synthesis pathway are retained in moss and are involved in morphology and division of chloroplasts. We isolated four genes that were related to peptidoglycan synthesis from the P. patens EST database, and are now using the gene-targeting technique developed for P. patens cells to resolve the relationship between the eukaryotic peptidoglycan synthesis pathway and chloroplast biogenesis.