Shoot Removal Induces Chloroplast Development in Roots via Cytokinin Signaling.

Abstract

The development of plant chloroplasts is regulated by various developmental, environmental, and hormonal cues. In Arabidopsis (Arabidopsis thaliana), chloroplast development is repressed in roots via auxin signaling. However, roots develop chloroplasts when they are detached from the shoot. In contrast to auxin, cytokinin positively affects chloroplast development in roots, but the role and signaling pathway of cytokinin in the root greening response remain unclear. To understand the regulatory pathways of chloroplast development in the plant stress response, we examined the mechanisms underlying the conditional greening of detached roots. In wild-type Arabidopsis roots, shoot removal activates type B ARABIDOPSIS RESPONSE REGULATOR (ARR)-mediated cytokinin signaling and induces chlorophyll accumulation and photosynthetic remodeling. ARR1 and ARR12 are essential for up-regulating nucleus- and plastid-encoded genes associated with chloroplast development in detached roots. In this process, WOUND INDUCED DEDIFFERENTIATION1 and class B GATA transcription factors (B-GATAs) act upstream and downstream of ARRs, respectively. Overexpression of B-GATAs promotes root greening, as does shoot removal, dependent on a light signaling transcription factor, LONG HYPOCOTYL5. Auxin represses the root greening response independent of ARR signaling. GNC-LIKE (GNL), a B-GATA, is strongly up-regulated in detached roots via ARR1 and ARR12 but is repressed by auxin, so GNL may function at the point of convergence of cytokinin and auxin signaling in the root greening response.

• Authors: Koichi Kobayashi, Ai Ohnishi, Daichi Sasaki, Sho Fujii, Akira Iwase, Keiko Sugimoto, Tatsuru Masuda, Hajime Wada
• Journal: Plant physiology (Plant Physiol) Vol. 173 Issue 4 Pg. 2340-2355 (04 2017) ISSN: 1532-2548 [Electronic] United States
• PMID: 28193764 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)
• Copyright: © 2017 American Society of Plant Biologists. All Rights Reserved.

Chemical References

• ARR1 protein, Arabidopsis
• ARR12 protein, Arabidopsis
• Arabidopsis Proteins
• Cytokinins
• DNA-Binding Proteins
• Plant Growth Regulators
• Transcription Factors
• Chlorophyll

Topics

• Arabidopsis Proteins (genetics, metabolism)
• Chlorophyll (metabolism)
• Chloroplasts (genetics, metabolism)
• Cytokinins (metabolism, pharmacology)
• DNA-Binding Proteins (genetics, metabolism)
• Electron Transport (drug effects, genetics)
• Gene Expression Regulation, Plant (drug effects)
• Meristem (genetics, metabolism)
• Microscopy, Fluorescence
• Mutation
• Photosynthesis (drug effects, genetics)
• Plant Growth Regulators (metabolism, pharmacology)
• Plant Leaves (genetics, metabolism)
• Plant Roots (genetics, metabolism)
• Reverse Transcriptase Polymerase Chain Reaction
• Signal Transduction
• Transcription Factors (genetics, metabolism)