ORIGINAL PAPER Variation in the enzyme activity and gene expression of myo-inositol-3-phosphate synthase and phytate accumulation during seed development in common bean (Phaseolus vulgaris L.) Cileide Maria Medeiros Coelho Æ Vagner Augusto Benedito Æ Antonio Figueira Æ Victor Alexandre Vitorello Æ Ricardo Antunes Azevedo Received: 28 June 2006 / Revised: 5 December 2006 / Accepted: 19 December 2006 / Published online: 15 February 2007 Ó Franciszek Go ´ rski Institute of Plant Physiology, Polish Academy of Sciences, Krako ´ w 2007 Abstract The most abundant form in which phos- phorus occurs in seeds is phytate (myo-inositol hexa- kisphosphate), mostly known as an antinutrient for animals, given its ability to complex proteins and minerals, despite its antioxidant and anticarcinogenic properties. However, phytate synthesis is still poorly understood, both in terms of its regulation and metabolic route, and relatively few works have addressed the control mechanism of phytate accumu- lation during seed development. Aiming at under- standing the control mechanism of phytate synthesis, we examined myo-inositol-3-phosphate synthase (MIPS) (EC 5.5.1.4) activity and gene expression dur- ing seed development of common bean. Phytate con- centration was low at the initial stage of seed development, coinciding with a period of the most in- tense seed metabolism, but followed by a period of high enzymatic activity and gene expression of MIPS when a decrease in its specific activity and transcription was detected throughout seed development until 20 days after flowering; however, the specific activity of MIPS dropped more expressively than the gene expression, matching with higher phytate concentra- tion. Hence, we show that there is evidence of one control point regulating phytate synthesis with MIPS enzyme. Keywords Inositol polyphosphate Á Myo-inositol Á Phytic acid Á Protein Á Phosphorus Abbreviations DAF Days after flowering IP Inositol phosphates Ins(3)P, MIPS, EC 5.5.1.4 Myo-inositol-3-phosphate synthase cDNA Deoxyribonucleic acid stand PCR Polymerase chain reaction RT Reverse transcriptase P Phosphorus MI-3P Myo-inositol 3-P MIK Myo-inositol kinase Introduction The most abundant form in which phosphorus occurs in seeds is phytate (myo-inositol hexakisphosphate, IP 6 ) where up to 80% of total seed phosphorus may be stored in this form (Raboy 1990). During seed devel- opment phytic acid is deposited within single-mem- brane storage organelles referred to as protein bodies (Lott et al. 1985) and can form insoluble complexes with minerals such as K, Mg, Mn, Ca, Fe and Zn via ionic associations with negatively charged phosphates, which is known as phytate or phytin (Lonnerdal 2002). Communicated by G. Klobus. C. M. M. Coelho (&) Centro Agroveterina ´ rio, Universidade do Estado de Santa Catarina, Av. Luiz de Camo ˜ es, 2090, Lages, SC CEP 88520-000, Brazil e-mail: a2cmm@cav.udesc.br V. A. Benedito Á A. Figueira Á V. A. Vitorello Centro de Energia Nuclear na Agricultura, Universidade de Sa ˜ o Paulo, Piracicaba, SP, Brazil R. A. Azevedo Escola Superior de Agricultura Luiz de Queiroz, Universidade de Sa ˜ o Paulo, Piracicaba, SP, Brazil 123 Acta Physiol Plant (2007) 29:265–271 DOI 10.1007/s11738-007-0033-6