Journal Article

The Bacterial Stringent Response, Conserved in Chloroplasts, Controls Plant Fertilization

Shinji Masuda, Kazuki Mizusawa, Takakuni Narisawa, Yuzuru Tozawa, Hiroyuki Ohta and Ken-ichiro Takamiya

in Plant and Cell Physiology

Published on behalf of Japanese Society of Plant Physiologists

Volume 49, issue 2, pages 135-141
Published in print February 2008 | ISSN: 0032-0781
Published online February 2008 | e-ISSN: 1471-9053 | DOI: http://dx.doi.org/10.1093/pcp/pcm177
The Bacterial Stringent Response, Conserved in Chloroplasts, Controls Plant Fertilization

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  • Biochemistry
  • Molecular and Cell Biology
  • Plant Sciences and Forestry

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The chloroplast, an essential organelle for plants, performs a wide variety of metabolic processes for host cells, which include photosynthesis as well as amino acid and fatty acid biosynthesis. The organelle conserves many bacterial systems in its functions, implicating its origin from symbiosis of a photosynthetic bacterium. In bacterial cells, the stringent response acts as a global regulatory system for gene expression mediated by a small nucleotide, guanosine 5′-diphosphate 3′-diphosphate (ppGpp), that is necessary for cell adaptation to diverse environmental stimuli such as amino acid starvation. Recent studies indicated that proteins similar to the bacterial ppGpp synthase/hydrolyase are conserved in plants, although their precise roles are not known. Here we show that the stringent response in chloroplasts is crucial for normal plant fertilization. Specifically, one of the Arabidopsis ppGpp synthase homologs, CRSH (Ca2+-activated RelA/SpoT homolog), exhibits calcium-dependent ppGpp synthesis activity in vitro, and is localized in chloroplasts in vivo. A knockdown mutation of CRSH in Arabidopsis results in a significant reduction in silique size and seed production, indicating that plant reproduction is under the control of chloroplast function through a ppGpp-mediated stringent response.

Keywords: Arabidopsis; Chloroplast; ppGpp; RelA; SpoT; Stringent response

Journal Article.  3937 words.  Illustrated.

Subjects: Biochemistry ; Molecular and Cell Biology ; Plant Sciences and Forestry

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