Phytate Transport by MRPs

Phytic acid is the main storage form for phosphate in plant seeds. From a nutritional point of view it decreases the seed value by chelating important minerals, such as iron, zinc, magnesium, and calcium. Therefore, the isolation of low phytic acid (lpa) mutants is considered a highly desirable objective in the genetic improvement of the nutritional quality of grain crops. On the other side phytic acid is a very important signaling molecule involved in development and hormonal regulation. The only phytic acid transporters characterized so far are proteins of the ABCC type. Some lpa mutants affected in these transporters have been isolated and characterized in Arabidopsis and in crops. Here we review advances in the characterization of these proteins and on the corresponding mutants. Moreover we propose an explanation on how mutations in these transporters may affect different aspects of cellular metabolism not only strictly related to phytic acid biosynthesis.