Journal Article

Ectopic Overexpression of The Transcription Factor <i> OsGLK1</i> Induces Chloroplast Development in Non-Green Rice Cells

Hidemitsu Nakamura, Masayuki Muramatsu, Makoto Hakata, Osamu Ueno, Yoshiaki Nagamura, Hirohiko Hirochika, Makoto Takano and Hiroaki Ichikawa

in Plant and Cell Physiology

Published on behalf of Japanese Society of Plant Physiologists

Volume 50, issue 11, pages 1933-1949
Published in print November 2009 | ISSN: 0032-0781
Published online October 2009 | e-ISSN: 1471-9053 | DOI: https://dx.doi.org/10.1093/pcp/pcp138

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For systematic and genome-wide analyses of rice gene functions, we took advantage of the full-length cDNA overexpresser (FOX) gene-hunting system and generated >12 000 independent FOX-rice lines from >25 000 rice calli treated with the rice-FOX Agrobacterium library. We found two FOX-rice lines generating green calli on a callus-inducing medium containing 2,4-D, on which wild-type rice calli became ivory yellow. In both lines, OsGLK1 cDNA encoding a GARP transcription factor was ectopically overexpressed. Using rice expression-microarray and northern blot analyses, we found that a large number of nucleus-encoded genes involved in chloroplast functions were highly expressed and transcripts of plastid-encoded genes, psaA, psbA and rbcL, increased in the OsGLK1-FOX calli. Transmission electron microscopy showed the existence of differentiated chloroplasts with grana stacks in OsGLK1-FOX calli cells. However, in darkness, OsGLK1-FOX calli did not show a green color or develop grana stacks. Furthermore, we found developed chloroplasts in vascular bundle and bundle sheath cells of coleoptiles and leaves from OsGLK1-FOX seedlings. The OsGLK1-FOX calli exhibited high photosynthetic activity and were able to grow on sucrose-depleted media, indicating that developed chloroplasts in OsGLK1-FOX rice calli are functional and active. We also observed that the endogenous OsGLK1 mRNA level increased synchronously with the greening of wild-type calli after transfer to plantlet regeneration medium. These results strongly suggest that OsGLK1 regulates chloroplast development under the control of light and phytohormones, and that it is a key regulator of chloroplast development.

Keywords: Chloroplast development • FOX hunting system • GARP transcription factor • OsGLK1 • Oryza sativa • Rice

Journal Article.  8407 words.  Illustrated.

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

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