Myo-inositol hexakisphosphate, isolated from female gametophyte tissue of loblolly pine, inhibits growth of early-stage somatic embryos.

• Myo-inositol hexakisphosphate (InsP(6)), abundant in animals and plants, is well known for its anticancer activity. However, many aspects of InsP(6) function in plants remain undefined. We now report the first evidence that InsP(6) can inhibit cellular proliferation in plants under growth conditions where phosphorus is not limited. • A highly anionic molecule inhibitory to early-stage somatic embryo growth of loblolly pine (LP) was purified chromatographically from late-stage LP female gametophytes (FGs), and then characterized structurally using mass spectrometry (MS) and nuclear magnetic resonance (NMR) analyses. • Exact mass and mass spectrometry-mass spectrometry (MS-MS) fragmentation identified the bioactive molecule as an inositol hexakisphosphate. It was then identified as the myo-isomer (i.e. InsP(6)) on the basis of (1)H-, (31)P- and (13)C-NMR, (1)H-(1)H correlation spectroscopy (COSY), (1)H-(31)P heteronuclear single quantum correlation (HSQC) and (1)H-(13)C HSQC. Topical application of InsP(6) to early-stage somatic embryos indeed inhibits embryonic growth. • Recently evidence has begun to emerge that InsP(6) may also play a regulatory role in plant cells. We anticipate that our findings will help to stimulate additional investigations aimed at elucidating the roles of inositol phosphates in cellular growth and development in plants.