Journal Article

Overexpression of a Type-A Response Regulator Alters Rice Morphology and Cytokinin Metabolism

Naoya Hirose, Nobue Makita, Mikiko Kojima, Tomoe Kamada-Nobusada and Hitoshi Sakakibara

in Plant and Cell Physiology

Published on behalf of Japanese Society of Plant Physiologists

Volume 48, issue 3, pages 523-539
Published in print March 2007 | ISSN: 0032-0781
Published online March 2007 | e-ISSN: 1471-9053 | DOI: http://dx.doi.org/10.1093/pcp/pcm022
Overexpression of a Type-A Response Regulator Alters Rice Morphology and Cytokinin Metabolism

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

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Genome-wide analyses of rice (Oryza sativa L.) cytokinin (CK)-responsive genes using the Affymetrix GeneChip® rice genome array were conducted to define the spectrum of genes subject to regulation by CK in monocotyledonous plants. Application of trans-zeatin modulated the expression of a wide variety of genes including those involved in hormone signaling and metabolism, transcriptional regulation, macronutrient transport and protein synthesis. To understand further the function of CK in rice plants, we examined the effects of in planta manipulation of a putative CK signaling factor on morphology, CK metabolism and expression of CK-responsive genes. Overexpression of the CK-inducible type-A response regulator OsRR6 abolished shoot regeneration, suggesting that OsRR6 acts as a negative regulator of CK signaling. Transgenic lines overexpressing OsRR6 (OsRR6-ox) had dwarf phenotypes with poorly developed root systems and panicles. Increased content of trans-zeatin-type CKs in OsRR6-ox lines indicates that homeostatic control of CK levels is regulated by OsRR6 signaling. Expression of genes encoding CK oxidase/dehydrogenase decreased in OsRR6-ox plants, possibly accounting for elevated CK levels in transgenic lines. Expression of a number of stress response genes was also altered in OsRR6-ox plants.

Keywords: Cytokinin; Gene chip; Microarray; Oryza sativa; Response regulator

Journal Article.  9429 words.  Illustrated.

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

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