Ji Chen1,2, Li Wang1, Xiaowan Jin1, Jian Wan1, Lang Zhang1, Byoung Il Je3, Ke Zhao1, Fanlei Kong1, Jin Huang4,5, Mengliang Tian6. 1. College of Agronomy, Sichuan Agricultural University, Chengdu, 611130, China. 2. Division of Applied Life Sciences (BK21+), Graduate School of Gyeongsang National University, Jinju, 660-701, Republic of Korea. 3. College of Ecology and Environment, Chengdu University of Technology, Chengdu, 61005, China. 4. Division of Applied Life Sciences (BK21+), Graduate School of Gyeongsang National University, Jinju, 660-701, Republic of Korea. huangjin18@cdut.edu.cn. 5. College of Ecology and Environment, Chengdu University of Technology, Chengdu, 61005, China. huangjin18@cdut.edu.cn. 6. Institute for New Rural Development, Sichuan Agricultural University, Yaan, 625000, China. secondat@sicau.edu.cn.
Abstract
BACKGROUND: The Spo0B-associated GTP-binding protein (Obg) GTPase, has diverse and important functions in bacteria, including morphological development, DNA replication and ribosome maturation. Homologs of the Bacillus subtilis Obg have been also found in chloroplast of Oryza sativa, but their primary roles remain unknown. RESULTS: We clarify that OsObgC1 is a functional homolog of AtObgC. The mutant obgc1-d1 exhibited hypersensitivity to the DNA replication inhibitor hydroxyurea. Quantitative PCR results showed that the ratio of chloroplast DNA to nuclear DNA in the mutants was higher than that of the wild-type plants. After DAPI staining, OsObgC1 mutants showed abnormal nucleoid architectures. The specific punctate staining pattern of OsObgC1-GFP signal suggests that this protein localizes to the chloroplast nucleoids. Furthermore, loss-of-function mutation in OsObgC1 led to a severe suppression of protein biosynthesis by affecting plastid rRNA processing. It was also demonstrated through rRNA profiling that plastid rRNA processing was decreased in obgc1-d mutants, which resulted in impaired ribosome biogenesis. The sucrose density gradient profiles revealed a defective chloroplast ribosome maturation of obgc1-d1 mutants. CONCLUSION: Our findings here indicate that the OsObgC1 retains the evolutionarily biological conserved roles of prokaryotic Obg, which acts as a signaling hub that regulates DNA replication and ribosome biogenesis in chloroplast nucleoids.
BACKGROUND: The Spo0B-associated GTP-binding protein (Obg) GTPase, has diverse and important functions in bacteria, including morphological development, DNA replication and ribosome maturation. Homologs of the Bacillus subtilis Obg have been also found in chloroplast of Oryza sativa, but their primary roles remain unknown. RESULTS: We clarify that OsObgC1 is a functional homolog of AtObgC. The mutant obgc1-d1 exhibited hypersensitivity to the DNA replication inhibitor hydroxyurea. Quantitative PCR results showed that the ratio of chloroplast DNA to nuclear DNA in the mutants was higher than that of the wild-type plants. After DAPI staining, OsObgC1 mutants showed abnormal nucleoid architectures. The specific punctate staining pattern of OsObgC1-GFP signal suggests that this protein localizes to the chloroplast nucleoids. Furthermore, loss-of-function mutation in OsObgC1 led to a severe suppression of protein biosynthesis by affecting plastid rRNA processing. It was also demonstrated through rRNA profiling that plastid rRNA processing was decreased in obgc1-d mutants, which resulted in impaired ribosome biogenesis. The sucrose density gradient profiles revealed a defective chloroplast ribosome maturation of obgc1-d1 mutants. CONCLUSION: Our findings here indicate that the OsObgC1 retains the evolutionarily biological conserved roles of prokaryotic Obg, which acts as a signaling hub that regulates DNA replication and ribosome biogenesis in chloroplast nucleoids.
Authors: Woo Young Bang; In Sil Jeong; Dae Won Kim; Chak Han Im; Chen Ji; Sung Min Hwang; Se Won Kim; Young Sim Son; Joa Jeong; Takashi Shiina; Jeong Dong Bahk Journal: Plant Cell Physiol Date: 2008-08-04 Impact factor: 4.927
Authors: Thomas J Bollenbach; Heike Lange; Ryan Gutierrez; Mathieu Erhardt; David B Stern; Dominique Gagliardi Journal: Nucleic Acids Res Date: 2005-05-12 Impact factor: 16.971