In vivo effects of NbSiR silencing on chloroplast development in Nicotiana Benthamiana

Yong Won Kang, Jae Yong Lee, Young Jeon, Gang Won Cheong, Moonil Kim, Hyun Sook Pai

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20 Citations (Scopus)


Sulfite reductase (SiR) performs dual functions, acting as a sulfur assimilation enzyme and as a chloroplast (cp-) nucleoid binding protein. In this study, we examined the in vivo effects of SiR deficiency on chloroplast development in Nicotiana benthamiana. Virus-induced gene silencing of NbSiR resulted in leaf yellowing and growth retardation phenotypes, which were not rescued by cysteine supplementation. NbSiR:GFP fusion protein was targeted to chloroplasts and colocalized with cp-nucleoids. Recombinant full-length NbSiR protein and the C-terminal half of NbSiR possessed cp-DNA compaction activities in vitro, and expression of full-length NbSiR in E. coli caused condensation of genomic DNA. NbSiR silencing differentially affected expression of plastid-encoded genes, inhibiting expression of several genes more severely than others. In the later stages, depletion of NbSiR resulted in chloroplast ablation. In NbSiR-silenced plants, enlarged cp-nucleoids containing an increased amount of cp-DNA were observed in the middle of the abnormal chloroplasts, and the cp-DNAs were predominantly of subgenomic sizes based on pulse field gel electrophoresis. The abnormal chloroplasts developed prolamellar body-like cubic lipid structures in the light without accumulating NADPH:protochlorophyllide oxidoreductase proteins. Our results suggest that NbSiR plays a role in cp-nucleoid metabolism, plastid gene expression, and thylakoid membrane development.

Original languageEnglish
Pages (from-to)569-583
Number of pages15
JournalPlant Molecular Biology
Issue number6
Publication statusPublished - 2010

Bibliographical note

Funding Information:
Acknowledgments The authors wish to thank Dr. Gregory A. Armstrong (Ohio State University, USA) for providing anti-POR antibodies. This research was supported by grants from the National Research Foundation of Korea (NRF) (No. 2009-0078406), from the BioGreen21 Program (RDA, Korea), and from the Plant Signaling Network Research Center (at Korea University) of the Science Research Center Program (No. 2009-0079421).

All Science Journal Classification (ASJC) codes

  • Agronomy and Crop Science
  • Genetics
  • Plant Science


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