IPS1, a non?protein coding gene, contains a motif with sequence complementarity to the phosphate (Pi) starvation?induced miRNA miR-399. Pairing of IPS1 and miR-399 is interrupted by a mismatched loop at the expected miRNA cleavage site. IPS1 RNA is not cleaved by miR-399 but instead sequesters miR-399. Overexpression of IPS1 results in increased accumulation of the PHO2 mRNA which is a target of miR-399 (Franco-Zorrilla et al., 2007). In rice two IPS genes, IPS1 and IPS2 has been identified (Huo et al., 2004). IPS1 showed much higher accumulation in rice roots than IPS2. Both the gens are independently responsive to Pi signaling and mainly express in lateral roots and vascular bundle in primary roots (Huo et al., 2004).