which are considered as one of the major transporter families in plants [44]. It has
been reported that the first isolated MATE transporters from in plants (specifically in
Arabidopsis) were involved in the detoxification of xenobiotics [45, 46]. Li and
co-authors [46] succeeded to characterize the first multi-specific MATE transporter
and named it AtDTX1 (for Arabidopsis thaliana detoxification 1). Moreover, they
demonstrated that AtDTX1 serves as an efflux carrier for the antibiotic norfloxacin
during functional screening with Escherichia coli KAM3 mutant. Furthermore, they
suggested that AtDTX1 is localized in the plasma membrane and consequently will
mediate the efflux of exogenous or plant-derived toxic compounds from the cytoplasm. PvOCT1 is the first protein linked to the SLC22 family and has been
identified in Phaseolus vulgaris [47]. The expression of PvOCT1 is upregulated
after exposure to the drought stress, and this presumes that it plays a role in stress
adaption. In 2007, Lelandais-Briere and co-workers [48] discovered AtOCT1
(a PvOCT1 homologous) that is localized in the plasma membrane of Arabidopsis
and can be characterized as carnitine transporter. The other five members of
A. thaliana OCT family (AtOCT2-AtOCT6) are localized in the tonoplast, and
their functions are still unknown; nevertheless, the expression of these genes was
upregulated during the exposure of Arabidopsis plants to drought, cold and salt
stress [49]. In a recent study, it was suggested that OCTs might provide an important
route for delivery of the antidiabetic drug metformin (MET) [50], showing that MET
transport was significantly affected in common cattail (Typha latifolia) roots after
addition of quinidine (OCTs inhibitor in mammals).
2.3 Translocation of Pharmaceuticals Within Different Plant
Parts
After organic contaminants (e.g. pharmaceuticals) entered the root, translocation
might occur to the aerial part of the plant via the vascular tissue. These compounds
can be transported upwards with water and other solutes by transpiration through
vessels and tracheids in the xylem (Fig. 2). Transpiration flow, driven by root
pressure and transpirational pulling, was shown to be the main driving force of the
translocation of pharmaceuticals [51].
During photosynthesis and to protect plants from overheating, stomatal
apparatus – specific ventilation pores – mostly present on the abaxial side of the
leaf are open for gas exchange or evaporative cooling. Mesophyllic cells located
above the stomata are transpiring water, leading to water deficiency and increased
negative water potential. To compensate this effect, the cell takes away water from
neighbouring cells, which results in a spreading suction force towards leaf vessels, to
xylem tracheids and finally to roots to take up water from the surrounding environment. A high light intensity (higher photosynthesis rates), warm temperature (which
increase saturation level of water vapour within leaves) and dry air or wind enhance
transpiration rates. Transpiration rates determine the flux of water and solutes and
Uptake and Translocation of Pharmaceuticals in Plants:. . .
111
been reported that the first isolated MATE transporters from in plants (specifically in
Arabidopsis) were involved in the detoxification of xenobiotics [45, 46]. Li and
co-authors [46] succeeded to characterize the first multi-specific MATE transporter
and named it AtDTX1 (for Arabidopsis thaliana detoxification 1). Moreover, they
demonstrated that AtDTX1 serves as an efflux carrier for the antibiotic norfloxacin
during functional screening with Escherichia coli KAM3 mutant. Furthermore, they
suggested that AtDTX1 is localized in the plasma membrane and consequently will
mediate the efflux of exogenous or plant-derived toxic compounds from the cytoplasm. PvOCT1 is the first protein linked to the SLC22 family and has been
identified in Phaseolus vulgaris [47]. The expression of PvOCT1 is upregulated
after exposure to the drought stress, and this presumes that it plays a role in stress
adaption. In 2007, Lelandais-Briere and co-workers [48] discovered AtOCT1
(a PvOCT1 homologous) that is localized in the plasma membrane of Arabidopsis
and can be characterized as carnitine transporter. The other five members of
A. thaliana OCT family (AtOCT2-AtOCT6) are localized in the tonoplast, and
their functions are still unknown; nevertheless, the expression of these genes was
upregulated during the exposure of Arabidopsis plants to drought, cold and salt
stress [49]. In a recent study, it was suggested that OCTs might provide an important
route for delivery of the antidiabetic drug metformin (MET) [50], showing that MET
transport was significantly affected in common cattail (Typha latifolia) roots after
addition of quinidine (OCTs inhibitor in mammals).
2.3 Translocation of Pharmaceuticals Within Different Plant
Parts
After organic contaminants (e.g. pharmaceuticals) entered the root, translocation
might occur to the aerial part of the plant via the vascular tissue. These compounds
can be transported upwards with water and other solutes by transpiration through
vessels and tracheids in the xylem (Fig. 2). Transpiration flow, driven by root
pressure and transpirational pulling, was shown to be the main driving force of the
translocation of pharmaceuticals [51].
During photosynthesis and to protect plants from overheating, stomatal
apparatus – specific ventilation pores – mostly present on the abaxial side of the
leaf are open for gas exchange or evaporative cooling. Mesophyllic cells located
above the stomata are transpiring water, leading to water deficiency and increased
negative water potential. To compensate this effect, the cell takes away water from
neighbouring cells, which results in a spreading suction force towards leaf vessels, to
xylem tracheids and finally to roots to take up water from the surrounding environment. A high light intensity (higher photosynthesis rates), warm temperature (which
increase saturation level of water vapour within leaves) and dry air or wind enhance
transpiration rates. Transpiration rates determine the flux of water and solutes and
Uptake and Translocation of Pharmaceuticals in Plants:. . .
111