This review will discuss recent progress in understanding the many roles of transporters in the whole-plant physiological processes that maintain iron (Fe) homeostasis. These processes include uptake from the soil via roots, control of transport from roots to above-ground parts of the plant, unloading of Fe from the xylem in above-ground parts, loading of Fe into mitochondria and plastids, transport of Fe to reproductive parts of the plant, and Fe mobilization during seed germination. In addition, we will discuss the mechanisms that plants use to cope with an apparently unintended consequence of Fe acquisition: the uptake of toxic heavy metals via Fe transporters. Rapid progress has been made in understanding the transport processes involved in each of these areas in the last 5 years and this review will focus on this recent progress. We will also highlight the key questions regarding transport steps that remain to be elucidated.
Widespread antibiotic resistance is a major public health concern, and plants represent an emerging antibiotic exposure route. Recent studies indicate that crop plants fertilized with antibiotic-laden animal manure accumulate antibiotics; however, the molecular mechanisms of antibiotic entry and subcellular partitioning within plant cells remain unknown. Here, we report that mutations in the Arabidopsis (Arabidopsis thaliana) locus Multiple Antibiotic Resistance1 (MAR1) confer resistance, while MAR1 overexpression causes hypersensitivity to multiple aminoglycoside antibiotics. Additionally, yeast expressing MAR1 are hypersensitive to the aminoglycoside G418. MAR1 encodes a protein with 11 putative transmembrane domains with low similarity to ferroportin1 from Danio rerio. A MAR1:yellow fluorescent protein fusion localizes to the chloroplast, and chloroplasts from plants overexpressing MAR1 accumulate more of the aminoglycoside gentamicin, while mar1-1 mutant chloroplasts accumulate less than the wild type. MAR1 overexpression lines are slightly chlorotic, and chlorosis is rescued by exogenous iron. MAR1 expression is also down-regulated by low iron. These data suggest that MAR1 is a plastid transporter that is likely to be involved in cellular iron homeostasis and allows opportunistic entry of multiple antibiotics into the chloroplast.
Background and objectives BK virus reactivation in kidney transplant recipients can lead to progressive allograft injury. Reduction of immunosuppression remains the cornerstone of treatment for active BK infection. Fluoroquinolone antibiotics are known to have in vitro antiviral properties, but the evidence for their use in patients with BK viremia is inconclusive. The objective of the study was to determine the efficacy of levofloxacin in the treatment of BK viremia.Design, setting, participants, & measurements Enrollment in this prospective, multicenter, double-blinded, placebo-controlled trial occurred from July 2009 to March 2012. Thirty-nine kidney transplant recipients with BK viremia were randomly assigned to receive levofloxacin, 500 mg daily, or placebo for 30 days. Immunosuppression in all patients was adjusted on the basis of standard clinical practices at each institution. Plasma BK viral load and serum creatinine were measured monthly for 3 months and at 6 months.Results At the 3-month follow-up, the percentage reductions in BK viral load were 70.3% and 69.1% in the levofloxacin group and the placebo group, respectively (P=0.93). The percentage reductions in BK viral load were also equivalent at 1 month (58% versus and 67.1%; P=0.47) and 6 months (82.1% versus 90.5%; P=0.38). Linear regression analysis of serum creatinine versus time showed no difference in allograft function between the two study groups during the follow-up period.Conclusions A 30-day course of levofloxacin does not significantly improve BK viral load reduction or allograft function when used in addition to overall reduction of immunosuppression.
PS secretion by brachypodium parallels that of related crop species such as barley and wheat. A single grass species-specific YSL clade is present, and expression of the BdYSL members of this clade could not be detected in shoots or roots, suggesting grass-specific functions in reproductive tissues. Finally, the Fe-responsive expression profiles of several YSLs suggest roles in Fe homeostasis.
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