Roles of MicroRNA in Regulation of Plant Phosphate Balance

The presence of microRNA molecules in the plant phloem sap suggests a long-distance control of gene expression. MicroRNAs (miRNA) are small molecules, consisting only of about 20 nucleotides. They are not translated into proteins, unlike other types of RNA. Scientists believe that they can down-regulate gene expression by facilitating the degradation of messenger RNA in a mechanism similar to RNA interference (RNAi) or by blocking the protein-translation machinery. miRNAs themselves are not translated into proteins. A group of scientists from the Max Planck Institute has discovered a particular miRNA responsible for the regulation of plant phosphate balance.

Levels of miRNA399 were found to be increased during inorganic phosphate (Pi) starvation. The miRNA targets a molecule that is critical for the maintenance Pi homeostasis. Inorganic phosphate is one of the most limiting mineral nutrients necessary for plant growth. The scientists hypothesized that during Pi limitation, miRNA accumulates in the roots so as to maintain shoot phosphate balance and thus optimizing shoot growth. Efficient Pi partitioning is important for plant productivity and survival during phosphate limitation. The discovery is among the firsts to functionally implicate an miRNA in an important biological process.

The open-access article is available at http://www.blackwell-synergy.com/doi/full/10.1111/j.1365-313X.2007.03363.x