RNAi-Mediated Silencing of ITPK Gene Reduces Phytic Acid Content,Alters Transcripts of Phytic Acid Biosynthetic Genes,and Modulates Mineral Distribution in Rice Seeds

Phytic acid is the principal storage form of phosphorus in plant seeds and an essential signalling molecule in several regulatory processes of plant development.However,it is known as an anti-nutrient compound owing to its potent chelating property.Thus,reducing the phytic acid content in crops is desirable.Studies involving regulation of MIPS and IPK1 genes to generate low phytate rice have been reported earlier.However,the functional significance of OsITPK and the effect of its down-regulation on phytic acid content and the associated pleiotropic effects on rice have not yet been investigated.In this study,tissue specific RNA interference(RNAi)-mediated down-regulation of a major ITPK homolog(OsITP5/6K-1)resulted in 46.2%decrease in phytic acid content of T2 transgenic seeds with a subsequent 3-fold enhancement in the inorganic phosphorus content.Silencing of OsITP5/6K-1 altered the transcript levels of essential phytic acid pathway genes,without significantly affecting the transcript levels of other OsITPK homologs.Furthermore,the mapping of elements through X-ray microfluorescence analysis revealed significant changes in the spatial distribution pattern and translocation of elements in low phytate seeds.Additionally,low phytate polished seeds exhibited 1.3-fold and 1.6-fold enhancement in iron and zinc content in the grain endosperm,respectively.Silencing of OsITP5/6K-1 also altered the amino acid and myo-inositol content of the transgenic seeds.Our results successfully established that RNAi-mediated silencing of OsITP5/6K-1 gene significantly reduced the phytate levels in seeds without hampering the germination potential of seeds and plant growth.The present study provided an insight into the mechanism of phytic acid biosynthesis pathway.

An Experimental Study on the Mechanism of Anisodamini Hydrobromidum in Treating Acute Ischemic Renal Failure

In order to explore the mechanism of anisodamini hydrobromidum (654-2) in treating acute ischemic renal failure, the model of acute ischemic renal failure in white New Zealand rabbits was established to dynamically observe and statistically analyze the intracellular concentration changes of free calcium([Ca(2+)]i) and inositol triphosphate (IP3). The results showed that the levels of [Ca(2+)], and IP3 in acute renal failure group were higher than those in control group (P<0. 01). However, the levels of [Ca(2+)]i and IP3 in 654-2 treated group were significantly lower than those in acute renal failure group (P<0. 001). It was concluded that 654-2 could alleviate Ca(2+)-overload in renal histocytes in acute ischemic renal failure. The protective mechanism is associated with intracellular reduction of IP3.

Isoflurane-induced neuronal apoptosis in developing hippocampal neurons

We hypothesized that the P2X7 receptor may be the target of isoflurane, so we investigated the roles of the P2X7 receptor and inositol triphosphate receptor in calcium overload and neuronal apoptosis induced by isoflurane in cultured embryonic rat hippocampal neurons. Results showed that isoflurane induced widespread neuronal apoptosis and significantly increased cytoplasmic Ca^2＋ Blockade of P2X7 receptors or removal of extracellular Ca^2＋ combined with blockade of inositol triphosphate receptors completely inhibited apoptosis or increase in cytoplasmic Ca^2＋. Removal of extracellular Ca^2＋ or blockade of inositol triphosphate receptor alone could partly inhibit these effects of isoflurane. Isoflurane could directly activate P2X7-gated channels and induce inward currents, but did not affect the expression of P2X7 receptor protein in neurons. These findings indicate that the mechanism by which isoflurane induced neuronal apoptosis in rat developing brain was mediated by intracellular calcium overload, which was caused by P2X7 receptor mediated calcium influx and inositol triphosphate receptor mediated calcium release.

Department of Etiology and Department of Pharmacology

In order to understand the role of transmembrane signal transduction of host cells in the early steps of infection,the adherence of E. coli to HEp 2 cells and the change of activity of phospholipase C γ (PLC γ) induced by the adherence were investigated.The adherence of enteropathogenic E.coli (EPEC), strain E.7, induced a significant increase of inositol triphosphat (IP 3) level in HEp 2 cells. The adherence of the bacteria and the increase of IP 3 was kinetically correlated. Whereas the increase of IP 3 level induced by the adherence of the control strain EPEC (H511), a non piliated strain, was much meager than that by E7, a piliated strain. The results highlighted an important role of transmembrane signals like IP 3 in the pathogenesis of EPEC.