Ectopic overexpression of the transcription factor osglk1 induces chloroplast development in non-green rice cells

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

Research output: Contribution to journalArticlepeer-review

73 Citations (Scopus)

Abstract

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.

Original languageEnglish
Pages (from-to)1933-1949
Number of pages17
JournalPlant and Cell Physiology
Volume50
Issue number11
DOIs
Publication statusPublished - Nov 2009

All Science Journal Classification (ASJC) codes

  • Physiology
  • Plant Science
  • Cell Biology

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