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JXB Advance Access published online on October 3, 2008
Journal of Experimental Botany, doi:10.1093/jxb/ern244
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© 2008 The Author(s).
This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/2.0/uk/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited. This paper is available online free of all access charges (see http://jxb.oxfordjournals.org/open_access.html for further details)

RESEARCH PAPER

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

Silvia Slavikova *, Shai Ufaz *, Tamar Avin-Wittenberg, Hanna Levanony and Gad Galili{dagger}

Department of Plant Sciences, The Weizmann Institute of Science, Rehovot 76100, Israel

{dagger} To whom correspondence should be addressed. E-mail: gad.galili{at}weizmann.ac.il

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.

Key words: Atg8, autophagy, cytokinin, cytokinin signalling, GFP, root architecture

* These authors contributed equally to this work

Received 24 June 2008; Revised 27 August 2008 Accepted 8 September 2008


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