In Posidonia oceanica cadmium induces changes in DNA methylation and chromatin patterning

In mammals, cadmium is widely considered as a non-genotoxic carcinogen acting through a methylation-dependent epigenetic mechanism. Here, the effects of Cd treatment on the DNA methylation patten are examined together with its effect on chromatin reconfiguration in Posidonia oceanica. DNA methylation level and pattern were analysed in actively growing organs, under short- (6 h) and long- (2 d or 4 d) term and low (10 μM) and high (50 μM) doses of Cd, through a Methylation-Sensitive Amplification Polymorphism technique and an immunocytological approach, respectively. The expression of one member of the CHROMOMETHYLASE (CMT) family, a DNA methyltransferase, was also assessed by qRT-PCR. Nuclear chromatin ultrastructure was investigated by transmission electron microscopy. Cd treatment induced a DNA hypermethylation, as well as an up-regulation of CMT, indicating that de novo methylation did indeed occur. Moreover, a high dose of Cd led to a progressive heterochromatinization of interphase nuclei and apoptotic figures were also observed after long-term treatment. The data demonstrate that Cd perturbs the DNA methylation status through the involvement of a specific methyltransferase. Such changes are linked to nuclear chromatin reconfiguration likely to establish a new balance of expressed/repressed chromatin. Overall, the data show an epigenetic basis to the mechanism underlying Cd toxicity in plants

Involvement of nitric oxide (NO) and auxin in signal transduction of copper induced morphological responses in Arabidopsis seedlings

Background and Aims Plants are able to adapt to the environment dynamically through regulation of their growth and development. Excess copper (Cu2+ ), a toxic heavy metal, induces morphological alterations in plant organs; however, the underlying mechanisms are still unclear. With this in mind, the multiple signalling functions of nitric oxide (NO) in plant cells and its possible regulatory role and relationship with auxin were examined during Cu2+ -induced morphological responses. Methods Endogenous auxin distribution was determined by microscopic observation of X-Gluc-stained DR5::GUS arabidopsis, and the levels of NO, superoxide and peroxynitrite were detected by ¿uorescence microscopy. As well as wild-type, NO-overproducer (nox1) and -de¿cient (nia1nia2 and nia1nia2noa1-2) arabidopsis plants were used. Key Results Cu2+ at a concentration of 50mM resulted in a large reduction in cotyledon area and hypocotyl and primary root lengths, accompanied by an increase in auxin levels. In cotyledons, a low Cu2+ concentration promoted NO accumulation, which was arrested by nitric oxide synthase or nitrate reductase inhibitors. The 5-mM Cu2+ -induced NO synthesis was not detectable in nia1nia2 or nia1nia2noa1-2 plants. In roots, Cu2+ caused a decrease of the NO level which was not associated with superoxide and peroxynitrite formation. Inhibition of auxin transport resulted in an increase in NO levels, while exogenous application of an NO donor reduced DR5::GUS expression. The elongation processes of nox1 were not sensitive to Cu2+ , but NO-de¿cient plants showed diverse growth responses. ConclusionsIn plant organs, Cu2+ excess results in severe morphological responses during which the endogenous hormonal balance and signal transduction are affected. Auxin and NO negatively regulate each other¿s level and NO intensi¿es the metal-induced cotyledon expansion, but mitigates elongation processes under Cu2+ exposurePetó, A.; Lehotai, N.; Lozano Juste, J.; Leon Ramos, J.; Tari, I.; Erdei, L.; Kolbert, Z. (2011). Involvement of nitric oxide (NO) and auxin in signal transduction of copper induced morphological responses in Arabidopsis seedlings. Annals of Botany. 108(3):449-457. doi:10.1093/aob/mcr176S449457108

Microarchitectural study of the augmented bone following ridge preservation with a porcine xenograft and a collagen membrane: preliminary report of a prospective clinical, histological, and micro-computed tomography analysis.

Socket preservation using a combination of porcine xenograft and collagen membrane maintains the vertical and horizontal dimensions of the ridge. The aim of this study was to evaluate the microarchitecture of the grafted area by histological analysis and micro-computed tomography. Patients in the test group (group 1; nine patients) underwent socket preservation, while the sockets in the control group (group 2; eight patients) were allowed to heal without preservation. After a 6-month healing period, bone core biopsy samples were obtained and implants were placed in the augmented sites in the test group (12 biopsy samples) and the non-augmented sockets of the control group (12 biopsy samples). Analysis of the biopsy samples obtained from group 1 revealed that particles of the graft were surrounded by newly formed bone in eight cases and by granulation tissue in four cases. Micromorphometric data showed statistically significant differences in several parameters between the microarchitecture of the native bone and the newly formed bone within the augmented sites, which suggests that the xenograft particles interfere with the bony healing of the alveoli