<p>NatA binds inositol hexakisphosphate and other ligands, and exhibits conformational flexibility dependent on the ligand bound.</p> / Dissertation

Phosphorus (P), a necessary plant and animal nutrient, can also lead to eutrophication of fresh waters when in excess. Appropriate P management is necessary to prevent fresh water pollution. Mineralogy of soil clays has been shown to affect P adsorption, desorption, and movement through soils. Specifically, hydroxy-interlayered minerals have been shown to adsorb and retain inorganic P in soil systems. This study was designed to determine the sorption and desorption characteristics of inorganic, organic, and mixed forms of P interacting with soil hydroxy-interlayered vermiculites (HIV) and smectites (HIS), and compare the findings to sorption and desorption processes of natural aluminum (Al) and Iron (Fe) hydroxide minerals. Results indicate natural Al and Fe hydroxide minerals sorbed and retained P more strongly than hydroxy-interlayered minerals in our samples and inositol hexakisphosphate was more highly sorbed and retained than inorganic P.

Thèse numérisée par la Division de la gestion de documents et des archives de l'Université de Montréal.

Thèse numérisée par la Division de la gestion de documents et des archives de l'Université de Montréal

myo-Inositol-1,2,3,4,5,6-hexakisphosphate (InsP6), also called phytic acid, is ubiquitous in eukaryotic cells and the most abundant inositol phosphate derivative. Loblolly pine (LP, Pinus taeda) constitutes the primary commercial species in the southern forest of U.S. Somatic embryogenesis (SE) is an effective technique to maintain the desirable genetic composition of the progeny and to accomplish the efficiency of propagation. SE can also serve as a tool for study of plant development. Unlike angiosperm embryos with attached cotyledons as seed storage organs, the diploid conifer embryo is surrounded by the unattached haploid female gametophyte (FG). In LP SE, FG tissue is absent in the embryogenic tissue culture. We found that extracts from early-stage FG stimulate growth and multiplication of early-stage somatic embryos, whereas FG water extracts from late stage contain substance(s) inhibitory to early-stage somatic embryo growth (DeSilva et al., 2007). We now present the isolation and identification of the inhibitory substance as InsP6 by means of water extraction, two gel filtrations and two ion exchange FPLC chromatographies. The results represent the first complete structural characterization of InsP6 from a natural product using LC/MS, LC/MS/MS, exact MS, 1D- and 2D-NMR analyses. We also report that there is a good correlation between the amount of InsP6 purified from FG tissue (1.3 nmoles per full-term FG) and the amount of InsP6 which inhibits somatic embryo growth. This novel approach of isolating and characterizing InsP6 from plant tissue, and investigating its role on SE can allow us to improve SE technology by circumventing current bottleneck, to elucidate enigmatic functions of InsP6 in plants, and most importantly, to utilize this molecule properly.