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Glutathione peroxidases (EC 1.11.1.9 and EC 1.11.1.12) catalyze the reduction of H2O2 or organic hydroperoxides to water or corresponding alcohols using reduced glutathione. Some glutathione peroxidase isozymes have a selenium‐dependent glutathione peroxidase activity and present a selenocysteine encoded by the opal TGA codon. In the present study, insights into the evolution of the whole glutathione peroxidase gene family were obtained after a comprehensive phylogenetic analysis using the improved number of glutathione peroxidase sequences recorded in the PeroxiBase database (http://peroxidase.isb-sib.ch/index.php). The identification of a common ancestral origin for the diverse glutathione peroxidase clusters was not possible. The complex relationships and evolutionary rates of this gene family suggest that basal glutathione peroxidase classes, present in all kingdoms, have originated from independent evolutionary events such as gene duplication, gene losses, lateral gene transfer among invertebrates and vertebrates or plants. In addition, the present study also emphasizes the possibility of some members being submitted to strong selective forces that probably dictated functional convergences of taxonomically distant groups.

Most multicellular organisms regulate developmental transitions by microRNAs, which are generated by an enzyme, Dicer. Insects and fungi have two Dicer-like genes, and many animals have only one, yet the plant, Arabidopsis, has four. Examining the poplar and rice genomes revealed that they contain five and six Dicer-like genes, respectively. Analysis of these genes suggests that plants require a basic set of four Dicer types which were present before the divergence of mono-and dicotyledonous plants (200 million years ago), but after the divergence of plants from green algae. A fifth type of Dicer seems to have evolved in monocots.

BackgroundSmall RNAs (19-24 nt) are key regulators of gene expression that guide both transcriptional and post-transcriptional silencing mechanisms in eukaryotes. Current studies have demonstrated that microRNAs (miRNAs) act in several plant pathways associated with tissue proliferation, differentiation, and development and in response to abiotic and biotic stresses. In order to identify new miRNAs in soybean and to verify those that are possibly water deficit and rust-stress regulated, eight libraries of small RNAs were constructed and submitted to Solexa sequencing.ResultsThe libraries were developed from drought-sensitive and tolerant seedlings and rust-susceptible and resistant soybeans with or without stressors. Sequencing the library and subsequent analyses detected 256 miRNAs. From this total, we identified 24 families of novel miRNAs that had not been reported before, six families of conserved miRNAs that exist in other plants species, and 22 families previously reported in soybean. We also observed the presence of several isomiRNAs during our analyses. To validate novel miRNAs, we performed RT-qPCR across the eight different libraries. Among the 11 miRNAs analyzed, all showed different expression profiles during biotic and abiotic stresses to soybean. The majority of miRNAs were up-regulated during water deficit stress in the sensitive plants. However, for the tolerant genotype, most of the miRNAs were down regulated. The pattern of miRNAs expression was also different for the distinct genotypes submitted to the pathogen stress. Most miRNAs were down regulated during the fungus infection in the susceptible genotype; however, in the resistant genotype, most miRNAs did not vary during rust attack. A prediction of the putative targets was carried out for conserved and novel miRNAs families.ConclusionsValidation of our results with quantitative RT-qPCR revealed that Solexa sequencing is a powerful tool for miRNA discovery. The identification of differentially expressed plant miRNAs provides molecular evidence for the possible involvement of miRNAs in the process of water deficit- and rust-stress responses.

The present study demonstrates that blood samples can be used as a source of miRNA identification associated to Parkinson's disease (PD). A set of six differentially expressed microRNAs were identified. They form two groups according to their expression profile in control, non-treated, early-onset and treated Parkinson's disease subjects. While miR-1, miR-22* and miR-29 expression levels allowed to distinguish non-treated PD from healthy subjects, miR-16-2*, miR-26a2* and miR30a differentiated treated from untreated patients. This study is innovative in contributing to the development of effective PD biomarkers.

Aerobic organisms evolved a complex antioxidant system, which protect the cells against oxidative damage caused by partially reduced oxygen intermediates, also known as reactive oxygen species. In plants, ascorbate peroxidases (EC, 1.11.1.11) catalyze the conversion of H(2)O(2) to H(2)O, using ascorbate as the specific electron donor in this enzymatic reaction. Previously, eight APx genes were identified in the rice (Oryza sativa L.) genome through in silico analysis: two cytosolic isoforms, two putative peroxisomal isoforms, and four putative chloroplastic ones. Using gene-specific probes, we confirmed the presence of the eight APx genes in the rice genome by Southern blot hybridization. Transcript accumulation analysis showed specific expression patterns for each member of the APx family according to developmental stage and in response to salt stress, revealing the complexity of the antioxidant system in plants. Finally, the subcellular localization of rice APx isoforms was determined using GFP-fusion proteins in BY-2 tobacco cells. In agreement with the initial prediction, OSAPX3 was localized in the peroxisomes. On the other hand, the OSAPX6-GFP fusion protein was found in mitochondria of the BY-2 cells, in contrast to the chloroplastic location predicted by sequence analysis. Our findings reveal the functional diversity of the rice APx genes and suggest complementation and coordination of the antioxidant defenses in different cellular compartments during development and abiotic stress.

Ascorbate peroxidase (APx) is a class I peroxidase that catalyzes the conversion of H(2)O(2) to H(2)O and O(2) using ascorbate as the specific electron donor. This enzyme has a key function in scavenging reactive oxygen species (ROS) and the protection against toxic effects of ROS in higher plants, algae, and Euglena. Here we report the identification of an APx multigene family in rice and propose a molecular evolutionary relationship between the diverse APx isoforms. In rice, the APx gene family has eight members, which encode two cytosolic, two putative peroxisomal, and four chloroplastic isoforms, respectively. Phylogenetic analyses were conducted using all APx protein sequences available in the NCBI databases. The results indicate that the different APx isoforms arose by a complex evolutionary process involving several gene duplications. The structural organization of APx genes also reflects this process and provides evidence for a close relationship among proteins located in the same subcellular compartment. A molecular evolutionary pathway, in which cytosolic and peroxisomal isoforms diverged early from chloroplastic ones, is proposed.

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