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Journal of Experimental Botany 2008 59(4):729-737; doi:10.1093/jxb/erm359
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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

Altered stomatal dynamics in ascorbate oxidase over-expressing tobacco plants suggest a role for dehydroascorbate signalling

Vasileios Fotopoulos1, Mario C. De Tullio2, Jeremy Barnes3 and Angelos K. Kanellis1,*

1Group of Biotechnology of Pharmaceutical Plants, Laboratory of Pharmacognocy, Department of Pharmaceutical Sciences, Aristotle University of Thessaloniki, 541 24 Thessaloniki, Greece
2Dipartimento di Biologia e Patologia Vegetale, Universita‘ di Bari, Via E. Orabona 4, I-70125 Bari, Italia
3Institute for Research on the Environment and Sustainability, Devonshire Bldg., Newcastle University, Newcastle upon Tyne NE1 7RU, UK

* To whom correspondence should be addressed. E-mail: kanellis{at}pharm.auth.gr

Control of stomatal aperture is of paramount importance for plant adaptation to the surrounding environment. Here, we report on several parameters related to stomatal dynamics and performance in transgenic tobacco plants (Nicotiana tabacum L., cv. Xanthi) over-expressing cucumber ascorbate oxidase (AO), a cell wall-localized enzyme of uncertain biological function that oxidizes ascorbic acid (AA) to monodehydroascorbic acid which dismutates yielding AA and dehydroascorbic acid (DHA). In comparison to WT plants, leaves of AO over-expressing plants exhibited reduced stomatal conductance (due to partial stomatal closure), higher water content, and reduced rates of water loss on detachment. Transgenic plants also exhibited elevated levels of hydrogen peroxide and a decline in hydrogen peroxide-scavenging enzyme activity. Leaf ABA content was also higher in AO over-expressing plants. Treatment of epidermal strips with either 1 mM DHA or 100 µM hydrogen peroxide resulted in rapid stomatal closure in WT plants, but not in AO-over-expressing plants. This suggests that signal perception and/or transduction associated with stomatal closure is altered by AO over-expression. These data support a specific role for cell wall-localized AA in the perception of environmental cues, and suggest that DHA acts as a regulator of stomatal dynamics.

Key words: ABA, apoplast, ascorbic acid, ascorbate oxidase, dehydroascorbic acid (DHA), hydrogen peroxide, Nicotiana tabacum L., cv. Xanthi, stomata, transgenic plants, water stress

Received 26 September 2007; Revised 11 December 2007 Accepted 12 December 2007


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