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A possible involvement of autophagy in amyloplast degradation in columella cells during hydrotropic response of Arabidopsis roots
- Source :
- Planta. 236(4)
- Publication Year :
- 2011
-
Abstract
- Seedling roots display not only gravitropism but also hydrotropism, and the two tropisms interfere with one another. In Arabidopsis (Arabidopsis thaliana) roots, amyloplasts in columella cells are rapidly degraded during the hydrotropic response. Degradation of amyloplasts involved in gravisensing enhances the hydrotropic response by reducing the gravitropic response. However, the mechanism by which amyloplasts are degraded in hydrotropically responding roots remains unknown. In this study, the mechanistic aspects of the degradation of amyloplasts in columella cells during hydrotropic response were investigated by analyzing organellar morphology, cell polarity and changes in gene expression. The results showed that hydrotropic stimulation or systemic water stress caused dramatic changes in organellar form and positioning in columella cells. Specifically, the columella cells of hydrotropically responding or water-stressed roots lost polarity in the distribution of the endoplasmic reticulum (ER), and showed accelerated vacuolization and nuclear movement. Analysis of ER-localized GFP showed that ER redistributed around the developed vacuoles. Cells often showed decomposing amyloplasts in autophagosome-like structures. Both hydrotropic stimulation and water stress upregulated the expression of AtATG18a, which is required for autophagosome formation. Furthermore, analysis with GFP-AtATG8a revealed that both hydrotropic stimulation and water stress induced the formation of autophagosomes in the columella cells. In addition, expression of plastid marker, pt-GFP, in the columella cells dramatically decreased in response to both hydrotropic stimulation and water stress, but its decrease was much less in the autophagy mutant atg5. These results suggest that hydrotropic stimulation confers water stress in the roots, which triggers an autophagic response responsible for the degradation of amyloplasts in columella cells of Arabidopsis roots.
- Subjects :
- Autophagosome
Time Factors
Recombinant Fusion Proteins
Gravitropism
Arabidopsis
Autophagy-Related Proteins
Plant Science
Hydrotropism
Vacuole
Endoplasmic Reticulum
Plant Roots
Tropism
Microscopy, Electron, Transmission
Gene Expression Regulation, Plant
Stress, Physiological
Botany
Genetics
Autophagy
Amyloplast
Plastids
Cell Nucleus
Microscopy, Confocal
biology
Dehydration
Arabidopsis Proteins
Endoplasmic reticulum
Cell Polarity
biology.organism_classification
Plants, Genetically Modified
Cell biology
Vacuolization
Seedlings
Mutation
Vacuoles
Transcription Factors
Subjects
Details
- ISSN :
- 14322048
- Volume :
- 236
- Issue :
- 4
- Database :
- OpenAIRE
- Journal :
- Planta
- Accession number :
- edsair.doi.dedup.....63f2e7b8ed7948321b6d4319d2982fde