Document Detail

A possible involvement of autophagy in amyloplast degradation in columella cells during hydrotropic response of Arabidopsis roots.
MedLine Citation:
PMID:  22532286     Owner:  NLM     Status:  Publisher    
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.
Mayumi Nakayama; Yasuko Kaneko; Yutaka Miyazawa; Nobuharu Fujii; Nahoko Higashitani; Shinya Wada; Hiroyuki Ishida; Kohki Yoshimoto; Ken Shirasu; Kenji Yamada; Mikio Nishimura; Hideyuki Takahashi
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Publication Detail:
Type:  JOURNAL ARTICLE     Date:  2012-4-25
Journal Detail:
Title:  Planta     Volume:  -     ISSN:  1432-2048     ISO Abbreviation:  -     Publication Date:  2012 Apr 
Date Detail:
Created Date:  2012-4-25     Completed Date:  -     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  1250576     Medline TA:  Planta     Country:  -    
Other Details:
Languages:  ENG     Pagination:  -     Citation Subset:  -    
Graduate School of Life Sciences, Tohoku University, Sendai, 980-8577, Japan.
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