Function of the Golgi-located phosphate transporter PHT4;6 is critical for senescence-associated processes in Arabidopsis.
The phosphate transporter PHT4;6 locates to the trans-Golgi compartment, and its impaired activity causes altered intracellular phosphate compartmentation, leading to low cytosolic Pi levels, a blockage of Golgi-related processes such as protein glycosylation and hemicellulose biosynthesis, and a dwarf phenotype. However, it was unclear whether altered Pi homeostasis in pht4;6 mutants causes further cellular problems, typically associated with limited phosphate availability. Here we report that pht4;6 mutants exhibit a markedly increased disposition to induce dark-induced senescence. In control experiments, in which pht4;6 mutants and wild-type plants developed similarly, we confirmed that accelerated dark-induced senescence in mutants is not a 'pleiotropic' process associated with the dwarf phenotype. In fact, accelerated dark-induced senescence in pht4;6 mutants correlates strongly with increased levels of toxic NH4 (+) and higher sensitivity to ammonium, which probably contribute to the inability of pht4;6 mutants to recover from dark treatment. Experiments with modified levels of either salicylic acid (SA) or trans-zeatin (tZ) demonstrate that altered concentrations of these compounds in pht4;6 plants act as major cellular mediators for dark-induced senescence. This conclusion gained further support from the notion that the expression of the pht4;6 gene is, in contrast to genes coding for major phosphate importers, substantially induced by tZ. Taken together, our findings point to a critical function of PHT4;6 to control cellular phosphate levels, in particular the cytosolic Pi availability, required to energize plant primary metabolism for proper plant development. Phosphate and its allocation mediated by PHT4;6 is critical to prevent onset of dark-induced senescence.
Plant Physiology, University of Kaiserslautern, Erwin-Schrödinger-Str., D-67653 Kaiserslautern, Germany.
Sebastian
S
Hassler
Plant Physiology, University of Kaiserslautern, Erwin-Schrödinger-Str., D-67653 Kaiserslautern, Germany.
Benjamin
B
Jung
Plant Physiology, University of Kaiserslautern, Erwin-Schrödinger-Str., D-67653 Kaiserslautern, Germany.
Lilia
L
Lemke
Laboratory of Growth Regulators, Centre of the Region Haná for Biotechnological and Agricultural Research, Palacký University & Institute of Experimental Botany ASCR, Šlechtitelů 11, CZ-78371 Olomouc, Czech Republic.
Ondřej
O
Novák
Laboratory of Growth Regulators, Centre of the Region Haná for Biotechnological and Agricultural Research, Palacký University & Institute of Experimental Botany ASCR, Šlechtitelů 11, CZ-78371 Olomouc, Czech Republic.
Miroslav
M
Strnad
Plant Biology, University of Zürich, Zürich, Switzerland.
Enrico
E
Martinoia
Plant Physiology, University of Kaiserslautern, Erwin-Schrödinger-Str., D-67653 Kaiserslautern, Germany neuhaus@rhrk.uni-kl.de.
H Ekkehard
HE
Neuhaus
D000375:Aging / Q000502:physiology*; D017360:Arabidopsis / Q000378:metabolism / Q000502:physiology*; D029681:Arabidopsis Proteins / Q000502:physiology*; D002734:Chlorophyll / Q000378:metabolism; D003583:Cytokinins / Q000378:metabolism; D018506:Gene Expression Regulation, Plant / Q000502:physiology; D006056:Golgi Apparatus / Q000378:metabolism / Q000502:physiology*; D008027:Light; D028061:Phosphate Transport Proteins / Q000502:physiology*
D029681:Arabidopsis Proteins; D003583:Cytokinins; C580850:PHT4;6 protein, Arabidopsis; D028061:Phosphate Transport Proteins; D002734:Chlorophyll
Ammonium; Golgi; cytokinin; phosphate; salicylic acid; senescence; sugars.