LEPS2, a phosphorus starvation-induced novel acid phosphatase from tomato

Phosphate (Pi) is one of the least available plant nutrients found in the s oil. A significant amount of phosphate is bound in organic forms in the rhi zosphere. Phosphatases produced by plants and microbes are presumed to conv ert organic phosphorus into available Pi, which is absorbed by plants. In t his study we describe the isolation and characterization of a novel tomato (Lycoersicon esculentum) phosphate starvation-induced gene (LePS2) represen ting an acid phosphatase. LePS2 is a member of a small gene family in tomat o. The cDNA is 942 bp long and contains an open reading frame encoding a 26 9-amino acid polypeptide. The amino acid sequence of LePS2 has a significan t similarity with a phosphatase from chicken. Distinct regions of the pepti de also share significant identity with the members of HAD and DDDD super f amilies of phosphohydrolases. Many plant homologs of LePS2 are found in the databases. The LePS2 transcripts are induced rapidly in tomato plant and c ell culture in the absence of Pi. However, the induction is repressible in the presence of Pi. Divided root studies indicate that internal Pi levels r egulate the expression of LePS2. The enhanced expression of LePS2 is a spec ific response to Pi starvation, and it is not affected by starvation of oth er nutrients or abiotic stresses. The bacterially (Escherichia coli) expres sed protein exhibits phosphatase activity against the synthetic substrate p -nitrophenyl phosphate. The pH optimum of the enzyme activity suggests that LePS2 is an acid phosphatase.