Plant Physiology Preview Published on June 28, 2007; 10.1104/pp.107.103762
OPEN ACCESS ARTICLE
Received June 12, 2007
Accepted June 22, 2007
Expression of a Constitutively Activated Plasma Membrane H+-ATPase Alters Plant Development and Increases Salt Tolerance
Frédéric Gévaudant , Geoffrey Duby , Erik von Stedingk , Rongmin Zhao , Pierre Morsomme , and Marc Boutry *
Unité de Biochimie Physiologique, Institut des Sciences de la Vie, Université catholique de Louvain, Croix du Sud 5-15, B-1348 Louvain-La-Neuve, Belgium
* Corresponding author; email: boutry{at}fysa.ucl.ac.be.
The plasma membrane proton pump ATPase (H+-ATPase) plays a major role in the activation of ion and nutrient transport and has been suggested to be involved in several physiological processes, such as cell expansion and salt tolerance. Its activity is regulated by a C-terminal auto-inhibitory domain that can be displaced by phosphorylation and the binding of regulatory 14-3-3 proteins, resulting in an activated enzyme. To better understand the physiological consequence of this activation, we have analyzed transgenic tobacco plants expressing either wild-type plasma membrane H+-ATPase 4 (wtPMA4) or a PMA4 mutant lacking the auto-inhibitory domain ( PMA4), generating a constitutively activated enzyme. Plants showing four-fold higher expression of wtPMA4 than untransformed plants did not display any unusual phenotype and their leaf and root external acidification rates were not modified, while their in vitro H+-ATPase activity was markedly increased. This indicates that, in vivo, H+-ATPase overexpression is compensated by downregulation of H+-ATPase activity. In contrast, plants that expressed PMA4 were characterized by a lower apoplastic and external root pH, abnormal leaf inclination and twisted stems, suggesting alterations in cell expansion. This was confirmed by in vitro leaf extension and curling assays. These data therefore strongly support a direct role of H+-ATPase in plant development. The PMA4 plants also displayed increased salt tolerance during germination and seedling growth, supporting the hypothesis that H+-ATPase is involved in salt tolerance.
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