Journal Article

An autophagy-associated Atg8 protein is involved in the responses of <i>Arabidopsis</i> seedlings to hormonal controls and abiotic stresses

Silvia Slavikova, Shai Ufaz, Tamar Avin-Wittenberg, Hanna Levanony and Gad Galili

in Journal of Experimental Botany

Published on behalf of Society for Experimental Biology

Volume 59, issue 14, pages 4029-4043
Published in print October 2008 | ISSN: 0022-0957
Published online October 2008 | e-ISSN: 1460-2431 | DOI:

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Eukaryotes contain a ubiquitous family of autophagy-associated Atg8 proteins. In animal cells, these proteins have multiple functions associated with growth, cancer, and degenerative diseases, but their functions in plants are still largely unknown. To search for novel functions of Atg8 in plants, the present report tested the effect of expression of a recombinant AtAtg8 protein, fused at its N-terminus to green fluorescent protein (GFP) and at its C-terminus to the haemagglutinin epitope tag, on the response of Arabidopsis thaliana plants to the hormones cytokinin and auxin as well as to salt and osmotic stresses. Expression of this AtAtg8 fusion protein modulates the effect of cytokinin on root architecture. Moreover, expression of this fusion protein also reduces shoot anthocyanin accumulation in response to cytokinin feeding to the roots, implying the participation of AtAtg8 in cytokinin-regulated root–shoot communication. External application of cytokinin leads to the formation of novel GFP–AtAtg8-containing structures in cells located in the vicinity of the root vascular system, which are clearly distinct in size and dynamic movement from the GFP–AtAtg8-containing autophagosome-resembling structures that were observed in root epidermis cells. Expression of the AtAtg8 fusion construct also renders the plants more sensitive to a mild salt stress and to a lesser extent to a mild osmotic stress. This sensitivity is also associated with various changes in the root architecture, which are morphologically distinct from those observed in response to cytokinin. The results imply multiple functions for AtAtg8 in different root tissues that may also be regulated by different mechanisms.

Keywords: Atg8; autophagy; cytokinin; cytokinin signalling; GFP; root architecture

Journal Article.  8311 words.  Illustrated.

Subjects: Plant Sciences and Forestry

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