Magnesium is an abundant divalent cation in plant cells and plays a critical role in many physiological processes. We have previously described the identification of a 10-member Arabidopsis gene family encoding putati...Magnesium is an abundant divalent cation in plant cells and plays a critical role in many physiological processes. We have previously described the identification of a 10-member Arabidopsis gene family encoding putative magnesium transport (MGT) proteins. Here, we report that a member of the MGT family, AtMGTS, functions as a dual-functional Mg-transporter that operates in a concentration-dependent manner, namely it serves as a Mg-importer at micromolar levels and facilitates the efflux in the millimolar range. The AtMGT5 protein is localized in the mitochondria, suggesting that AtMGTS mediates Mg-trafficking between the cytosol and mitochondria. The AtMGT5 gene was exclusively expressed in anthers at early stages of flower development. Examination of two independent T-DNA insertional mutants of AtMGT5 gene demonstrated that AtMGT5 played an essential role for pollen development and male fertility. This study suggests a critical role for Mg^2+ transport between cytosol and mitochondria in male gametogenesis in plants.展开更多
Magnesium (Mg^2+) is one of the essential cations in all cells. Although the Mg^2+ transport mechanism has been well- documented in bacteria, less is known about Mg^2+ transporters in eukaryotes. The AtMGT gene f...Magnesium (Mg^2+) is one of the essential cations in all cells. Although the Mg^2+ transport mechanism has been well- documented in bacteria, less is known about Mg^2+ transporters in eukaryotes. The AtMGT gene family encoding putative magnesium transport proteins had been described previously. We report here that one of the Arabidopsis MGT family members, the AtMGT7 gene, encodes two mRNAs that have resulted from alternative splicing variants, designated AtMGT7a and AtMGT7b. Interestingly, the two mRNA variants were expressed with different patterns with AtMG77a expressing in all organs, but AtMGT7b appearing only in root and flowers. The AtMGT7a variant functionally complemented a bacterial mutant lacking Mg^2+ transport capacity, whereas AtMGT7b did not. The 63Ni^2+ tracer uptake analysis in the bacterial model showed that AtMGT7a mediated low-affinity transport of Mg^2+. Consistent with the complementation assay result, 63Ni^2+ tracer uptake analysis revealed that AtMGT7b did not transport Mg^2+. This study therefore has identified from a higher plant the first low-affinity Mg^2+ transporter encoded by a gene with alternatively spliced transcripts that produce proteins with distinct functions.展开更多
基金Acknowledgments We are grateful to Dr Michael E Maguire (Case Western Reserve University, USA) for providing the Salmonella mutant strain MM281 and advice on tracer uptake. This work was supported by grants from National Natural Science Foundation of China (30370794), Hunan Young Scientist Program (03JJY1003), and Hunan Provincial NSFC (08JJ3088).
文摘Magnesium is an abundant divalent cation in plant cells and plays a critical role in many physiological processes. We have previously described the identification of a 10-member Arabidopsis gene family encoding putative magnesium transport (MGT) proteins. Here, we report that a member of the MGT family, AtMGTS, functions as a dual-functional Mg-transporter that operates in a concentration-dependent manner, namely it serves as a Mg-importer at micromolar levels and facilitates the efflux in the millimolar range. The AtMGT5 protein is localized in the mitochondria, suggesting that AtMGTS mediates Mg-trafficking between the cytosol and mitochondria. The AtMGT5 gene was exclusively expressed in anthers at early stages of flower development. Examination of two independent T-DNA insertional mutants of AtMGT5 gene demonstrated that AtMGT5 played an essential role for pollen development and male fertility. This study suggests a critical role for Mg^2+ transport between cytosol and mitochondria in male gametogenesis in plants.
基金Supported by the National Natural Science Foundation of China (30370794)Hunan Provincial Natural Science Foundation for Excellent Youth Scholar (03JJY1003).
文摘Magnesium (Mg^2+) is one of the essential cations in all cells. Although the Mg^2+ transport mechanism has been well- documented in bacteria, less is known about Mg^2+ transporters in eukaryotes. The AtMGT gene family encoding putative magnesium transport proteins had been described previously. We report here that one of the Arabidopsis MGT family members, the AtMGT7 gene, encodes two mRNAs that have resulted from alternative splicing variants, designated AtMGT7a and AtMGT7b. Interestingly, the two mRNA variants were expressed with different patterns with AtMG77a expressing in all organs, but AtMGT7b appearing only in root and flowers. The AtMGT7a variant functionally complemented a bacterial mutant lacking Mg^2+ transport capacity, whereas AtMGT7b did not. The 63Ni^2+ tracer uptake analysis in the bacterial model showed that AtMGT7a mediated low-affinity transport of Mg^2+. Consistent with the complementation assay result, 63Ni^2+ tracer uptake analysis revealed that AtMGT7b did not transport Mg^2+. This study therefore has identified from a higher plant the first low-affinity Mg^2+ transporter encoded by a gene with alternatively spliced transcripts that produce proteins with distinct functions.