Localization of myo-inositol phosphate synthase (GmMIPS-1) during the early stages of soybean seed development

As a precursor to a large variety of compounds, myo-inositol is a central molecule required for cell metabolism and plant growth. The de novo synthesis of myo-inositol requires the activity of the enzyme D-myo-inositol-3-phosphate synthase (MIPS). MIPS cDNAs encoding one or more isoforms have been cloned from a number of species, nevertheless, little is known about the regulation of MIPS expression in developing seed. Seed-specific expression of a soybean isoform (GmMIPS-1) has been demonstrated, but tissue-specific localization during embryo development has not been reported. Using immunolocalization techniques, a specialized area of GmMIPS-1 expression was identified in the outer integumentary layer during early soybean seed development. In addition, localization data provided evidence that MIPS was associated with oxalate crystal idioblasts.     

ATXR5/6 Forms Alternative Protein Complexes with PCNA and the Nucleosome Core Particle

The proliferating cell nuclear antigen (PCNA) is a sliding clamp associated with DNA polymerases and serves as a binding platform for the recruitment of regulatory proteins linked to DNA damage repair, cell cycle regulation, and epigenetic signaling. The histone H3 lysine-27 (H3K27) mono-methyltransferase Arabidopsis trithorax-related protein 5/6 (ATXR5/6) associates with PCNA, and this interaction has been proposed to act as a key determinant controlling the reestablishment of H3K27 mono-methylation following replication. In this study, we provide biochemical evidence showing that PCNA inhibits ATXR6 enzymatic activity. The structure of the ATXR6 PCNA-interacting peptide (PIP) in complex with PCNA indicates that a trio of hydrophobic residues contributes to the binding of the enzyme to the sliding clamp. Finally, despite the presence of three PIP binding clefts, only two molecules of ATXR6 bind to PCNA likely enabling the recruitment of a third protein to the sliding clamp. Collectively, these results rule out the model wherein PCNA-bound ATXR6 actively reestablishes H3K27 mono-methylation following DNA replication and provides insights into the role of ATXR6 PIP motif in its interaction with PCNA.     

Expression of sucrose: fructan 6-fructosyltransferase (6-SFT) and myo -inositol 1-phosphate synthase (MIPS) genes in barley (Hordeum vulgare) leaves

Fructan is an important class of non-structural carbohydrates present in cool-season grasses. Sucrose: fructan 6-fructosyltransferase (6-SFT, EC 2.4.1.10), one of the enzymes thought to be involved in grass fructan biosynthesis, catalyzes the initiation and extension of 2,6-linked fructans.Myo-inositol is a central component in several metabolic pathways in higher plants.Myo-inositol 1-phosphate synthase (MIPS) (EC 5.5.1.4), the first enzyme in inositolde novo biosynthesis, catalyzes the formation ofmyo-inositol 1-phosphate (MIP) from glucose-6-phosphate. The expression of 6-SFT and MIPS genes is compared in barley (Hordeum vulgare L.) leaves under various conditions. In cool temperature treatments, both 6-SFT and MIPS mRNAs accumulate within two days and then decline after four days. Under warm temperatures and continuous illumination, the amount of 6-SFT and MIPS mRNA gradually accumulated in detached leaves and increased significantly by 8 h. In contrast, we observed no significant changes over time in attached (control) leaves. Treating detached leaves with glucose or sucrose in the dark resulted in accumulations of both 6-SFT and MIPS mRNA. Homologous expression patterns for 6-SFT and MIPS genes suggest that they may be similarly regulated in barley leaves. Although sucrose and glucose may play important roles in the expression of 6-SFT and MIPS genes, regulation likely involves multiple factors.