Characterized right here. Nevertheless, our calculations suggest that the estimated vacuolar ABA-GE
Characterized here. Nevertheless, our calculations recommend that the estimated vacuolar ABA-GE accumulation would be reached inside two h in the assumed continuous cytosolic ABA-GE concentration. Moreover, ABA-GE levels in leaves had been shown to be somewhat continual and only to substantially boost through repeated drought pressure cycles (Boyer and Zeevaart, 1982). Therefore, in spite of the low affinity for ABA-GE, the identified vacuolar ABA-GE import mechanisms are possiblyPlant Physiol. Vol. 163,Vacuolar Abscisic Acid Glucosyl Ester Import Mechanismsadequate for the maintenance of vacuolar ABA-GE levels in vivo beneath typical circumstances and presumably also can accommodate increasing cytosolic ABA-GE levels that take place (e.g. during drought tension situations). The energized transport of CYP1 Molecular Weight glucosides of secondary metabolites and xenobiotics into plant vacuoles is nicely documented. The anthocyanin malvidin-3-O-glucoside is transported into vacuoles of grape (Vitis vinifera) berries by the ABCC transporter ABCC1 from grape (Francisco et al., 2013). Proton gradient-dependent vacuolar transport mechanisms had been reported for diverse flavonoid glucosides (Klein et al., 1996; Frangne et al., 2002; Zhao and Dixon, 2009; Zhao et al., 2011). Furthermore, the vacuolar import mechanism of certain Glc conjugates was located to become species or tissue distinct. Salicylic acid glucoside is transported into vacuoles from Akt2 medchemexpress tobacco (Nicotiana tabacum) culture cells by protondependent transport mechanisms and into vacuoles from soybean (Glycine max) hypocotyls by ABC-type transport mechanisms (Dean and Mills, 2004; Dean et al., 2005). The glucoside of coniferyl alcohol was shown to become transported into endomembrane-enriched vesicles isolated from differentiating xylem of poplar (Populus spp.) by means of proton antiporters and into Arabidopsis leaf mesophyll vacuoles by means of ABC transporters (Miao and Liu, 2010; Tsuyama et al., 2013). Moreover, concurrent ABC-type and proton-dependent vacuolar transport mechanisms have been shown for the flavone diglucoside saponarin (Frangne et al., 2002). Hence, our findings on the simultaneous transport of ABA-GE by proton-dependent and ABC-type mechanisms are in agreement with previous reports on the vacuolar import of glucosides. The reported Km values of those vacuolar transports have been in range of 10 to 100 mM, that is 10- to 100-fold reduced than the apparent Km of the ABA-GE import. However, the Vmax with the ABA-GE uptake was higher compared with some reported glucoside transports, including that of saponarin (Frangne et al., 2002). The vacuolar membrane localization of Arabidopsis ABCC-type transporters and also the recent demonstration that grape ABCC1 mediates the vacuolar transport of anthocyanidin glucosides (Kang et al., 2011; Francisco et al., 2013) recommended the participation of ABCC-type transporters in vacuolar ABA-GE accumulation. The Arabidopsis AtABCC1 and in particular AtABCC2 mediate the transport of structurally diverse metabolites, which include phytochelatins, folates, and conjugates of chlorophyll catabolite and xenobiotics (Liu et al., 2001; Frelet-Barrand et al., 2008; Raichaudhuri et al., 2009; Song et al., 2010). We expressed AtABCC2 in yeast and observed a distinct MgATP-dependent ABA-GE transport activity of isolated membrane vesicles (Fig. six). This transport was nearly completely abolished within the presence of ABC transporter inhibitors (Table II). We additionally tested AtABCC1, the closest paralog of AtABCC2. Additionally, it mediated MgATP-dependent.