Garcia-Molina A.,University of Valencia |
Andres-Colas N.,University of Valencia |
Perea-Garcia A.,University of Valencia |
Del Valle-Tascon S.,University of Valencia |
And 3 more authors.
Plant Journal | Year: 2011
Copper is an essential micronutrient that functions as a redox cofactor in multiple plant processes, including photosynthesis. Arabidopsis thaliana possesses a conserved family of CTR-like high-affinity copper transport proteins denoted as COPT1-5. COPT1, the only family member that is functionally characterized, participates in plant copper acquisition. However, little is known about the function of the other Arabidopsis COPT proteins in the transport and distribution of copper. Here, we show that a functional fusion of COPT5 to the green fluorescent protein localizes in Arabidopsis cells to the prevacuolar compartment. Plants defective in COPT5 do not exhibit any significant phenotype under copper-sufficient conditions, but their growth is compromised under copper limitation. Under extreme copper deficiency, two independent copt5 knockout mutant lines exhibit severe defects in vegetative growth and root elongation, low chlorophyll content, and impairment in the photosynthetic electron transfer. All these phenotypes are rescued when the wild-type copy of the COPT5 gene is retransformed into a copt5 knockout line or when copper, but not other metals, are added to the medium. COPT5 is expressed in vascular tissues, with elevated levels in roots. Taken together, these results suggest that COPT5 plays an important role in the plant response to environmental copper scarcity, probably by remobilizing copper from prevacuolar vesicles, which could act as internal stores or recycling vesicles to provide the metal cofactor to key copper-dependent processes such as photosynthesis. © 2011 The Authors. The Plant Journal © 2011 Blackwell Publishing Ltd.
Calatayud M.,Institute Agroquymica Y Tecnologya Of Alimentos Csic |
Gimeno J.,Institute Agroquymica Y Tecnologya Of Alimentos Csic |
Velez D.,Institute Agroquymica Y Tecnologya Of Alimentos Csic |
Devesa V.,Institute Agroquymica Y Tecnologya Of Alimentos Csic |
Montoro R.,Institute Agroquymica Y Tecnologya Of Alimentos Csic
Chemical Research in Toxicology | Year: 2010
Many toxicological studies have been conducted with arsenic species in target organ cell lines. However, although epithelial gastrointestinal cells constitute the first barrier to the absorption of contaminants, studies using intestinal cells are scarce. The present study examines absorption through the intestinal epithelium of the pentavalent arsenic species most commonly found in foods [arsenate, As(V); monomethylarsonic acid, MMA(V); and dimethylarsinic acid, DMA(V)], using the Caco-2 cell line as a model. Different concentrations (1.3-667.6 μ M) and culture conditions (media, pH, addition of phosphates, and treatment with ethylenediaminetetraacetic acid) were evaluated to characterize such transport. The apparent permeabilities indicate that the methylated species show low absorption, whereas As(V) is a compound with moderate absorption. The kinetic study shows only a saturable component for MMA(V) transport in the range of concentrations assayed. The existence of paracellular transport was shown for all of the species, with greater significance in the case of the methylated forms. As(V) absorption was inhibited by 10 mM phosphate, and a phosphate transporter therefore could take part in intestinal absorption. Acidification of the medium (pH 5.5) resulted in a marked increase in As(V) and DMA(V) permeability (4-8 times, respectively) but not in MMA(V) permeability. This makes it necessary to consider the possible existence of absorption in the proximal intestine and even in the stomach, where the environment is acidic; alternatively, an H+-dependent transporter may be involved. The results obtained constitute the basis for future research on the mechanisms involved in the intestinal absorption of arsenic and its species, a decisive step in relation to their toxic action. © 2010 American Chemical Society.