An endoplasmic reticulum magnesium transporter is essential for pollen development in Arabidopsis

Magnesium is one of the essential macro-elements for plant growth and development, participated in photosynthesis and various metabolic processes. The Mg-transport abilities of the AtMGT (Magnesium Transporter) genes were identified in bacteria or yeast mutant system. In our previous studies, both the AtMGT5 and AtMGT9 were found essential for pollen development in Arabidopsis. Here we report another AtMGT member, AtMGT4, which was localized to the endoplasmic reticulum, was essential for pollen development as well. AtMGT4 expressed notably in pollen grains from bicellular pollen stage to mature pollen stage. A T-DNA insertional mutant of the gene, named mgt4-1, showed pollen abortive phenotype, thus we could not get any homozygous mutant from progenies of self-crossed +/mgt4-1 plants. Meanwhile, nearly half of pollens in AtMGT4-RNAi transgenic lines were sterile, consistent with the phenotype of +/mgt4-1 mutant. Transgenic plants expressing AtMGT4 in the mgt4-1 background could recover the pollen fertility to the wild type. Together, our findings demonstrated that the disruption of AtMGT4 in Arabidopsis could cause a defect of pollen development. The visible pollen abortion appeared at bicellular pollen stage in +/mgt4-1.