The H3K9me2-binding protein AGDP3 limits DNA methylation and transcriptional gene silencing in Arabidopsis.

DNA methylation, a conserved epigenetic mark, is critical for tuning temporal and spatial gene expression. The Arabidopsis thaliana DNA glycosylase/lyase REPRESSOR OF SILENCING 1 (ROS1) initiates active DNA demethylation and is required to prevent DNA hypermethylation at thousands of genomic loci. However, how ROS1 is recruited to specific loci is not well understood. Here, we report the discovery of Arabidopsis AGENET Domain Containing Protein 3 (AGDP3) as a cellular factor that is required to prevent gene silencing and DNA hypermethylation. AGDP3 binds to H3K9me2 marks in its target DNA via its AGD12 cassette. Analysis of the crystal structure of the AGD12 cassette of AGDP3 in complex with an H3K9me2 peptide revealed that dimethylated H3K9 and unmodified H3K4 are specifically anchored into two different surface pockets. A histidine residue located in the methyllysine binding aromatic cage provides AGDP3 with pH-dependent H3K9me2 binding capacity. Our results uncover a molecular mechanism for the regulation of DNA demethylation by the gene silencing mark H3K9me2.

Molecular characterization of AwSox2 from bivalve Anodonta woodiana: Elucidating its player in the immune response.

Sox2 is an embryonal stem cell Ag essential for early embryonic development, tissue homeostasis and immune regulation. In the current study, one complete Sox2 cDNA sequence was cloned from freshwater bivalve Anodonta woodiana and named AwSox2. Histological changes of testis derived from Bisphenol A (BPA) treatment were analyzed by hematoxylin and eosin staining. Expressions of AwSox2 derived from BPA, LPS and polyinosinic:polycytidylic (Poly I:C) challenge were measured by quantitative real-time PCR. The full-length cDNA of AwSox2 contained an open reading frame of 927 nucleotides bearing the typical structural features of Sox2 family. Obvious degeneration, irregular arrangement of spermatids, and clotted dead and intertwined spermatids were observed in BPA-treated groups. Administration of BPA could result in a dose-dependent up-regulation of AwSox2 expression in the male gonadal tissue of A. woodiana. In addition, expression of AwSox2 was significantly induced by LPS and Poly I:C treatment in the hepatopancreas, gill and hemocytes, compared with that of control group. These results indicated that up-regulations of AwSOx2 are closely related to apoptosis of spermatogonial stem cells derived from BPA treatment as well as enhancement of immune defense against LPS and Poly I:C challenge in A. woodiana.

Role of Eclipta prostrata extract in improving spatial learning and memory deficits in D-galactose-induced aging in rats.

OBJECTIVE: To investigate the role of Eclipta prostrata (E. prostrata) extract in improving spatial learning and memory deficits in D-galactose-induced aging in rats. METHODS: Rats were divided into five groups, with 10 animals in each group. Aging rats were produced by treatment with 100 mg·kg-1·d-1 of D-galactose for 6 weeks. Rats in the E. prostrata treatment groups received an aqueous extract of E. prostrata orally at a concentration of 50, 100, or 200 mg·kg-1·d-1 for 3 weeks. Animals in both the normal and model groups were treated with similar volumes of saline. Spatial memory performance was measured using the Morris water maze. The mRNA levels and enzyme activities of superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx) and glutathione reductase (GR) were analyzed using real-time quantitative PCR and spectrophotometry, respectively. The levels of induced nitric oxide synthase (iNOS), nitric oxide (NO), dopamine (DA), norepinephrine (NE), and serotonin (5-HT) were determined using enzyme-linked immunosorbent assay and spectrophotometry. RESULTS: Compared with the normal group, rats in the D-galactose-treated model group exhibited significant memory loss. There was severe damage to the hippocampal CA1 area, and expression levels of SOD, CAT, GPx, and GR were significantly decreased in the model group compared with the normal group. In the model group, levels of iNOS and NO were significantly increased compared with the normal group. However, treatment with E. prostrata extract reversed the conditions caused by D-galactose-induced aging, especially in the groups with higher treatment concentrations. Compared with the normal group, the levels of DA, NE, and 5-HT were significantly lower in the D-galactose-treated model group. In the E. prostrata extract-treated groups, however, there was a dose-dependent upregulation of DA, NE, and 5-HT expression. CONCLUSION: Our results suggest that administration of E. prostrata extract can result in an improvement in the learning and memory impairments that are induced by D-galactose treatment in rats. This improvement may be the result of enhanced antioxidative ability, decreased iNOS and NO levels, and the induction of DA, NE, and 5-HT expression in the brain.

Inositol Pyrophosphate InsP8 Acts as an Intracellular Phosphate Signal in Arabidopsis.

The maintenance of cellular phosphate (Pi) homeostasis is of great importance in living organisms. The SPX domain-containing protein 1 (SPX1) proteins from both Arabidopsis and rice have been proposed to act as sensors of Pi status. The molecular signal indicating the cellular Pi status and regulating Pi homeostasis in plants, however, remains to be identified, as Pi itself does not bind to the SPX domain. Here, we report the identification of the inositol pyrophosphate InsP8 as a signaling molecule that regulates Pi homeostasis in Arabidopsis. Polyacrylamide gel electrophoresis profiling of InsPs revealed that InsP8 level positively correlates with cellular Pi concentration. We demonstrated that the homologs of diphosphoinositol pentakisphosphate kinase (PPIP5K), VIH1 and VIH2, function redundantly to synthesize InsP8, and that the vih1 vih2 double mutant overaccumulates Pi. SPX1 directly interacts with PHR1, the central regulator of Pi starvation responses, to inhibit its function under Pi-replete conditions. However, this interaction is compromised in the vih1 vih2 double mutant, resulting in the constitutive induction of Pi starvation-induced genes, indicating that plant cells cannot sense cellular Pi status without InsP8. Furthermore, we showed that InsP8 could directly bind to the SPX domain of SPX1 and is essential for the interaction between SPX1 and PHR1. Collectively, our study suggests that InsP8 is the intracellular Pi signaling molecule serving as the ligand of SPX1 for controlling Pi homeostasis in plants.