The mitochondrial oxidation resistance protein AtOXR2 increases plant biomass and tolerance to oxidative stress.

This study demonstrates the existence of the oxidation resistance (OXR) protein family in plants. There are six OXR members in Arabidopsis that contain the highly conserved TLDc domain that is characteristic of this eukaryotic protein family. AtOXR2 is a mitochondrial protein able to alleviate the stress sensitivity of a yeast oxr1 mutant. It was induced by oxidative stress and its overexpression in Arabidopsis (oeOXR2) increased leaf ascorbate, photosynthesis, biomass, and seed production, as well as conferring tolerance to methyl viologen, antimycin A, and high light intensities. The oeOXR2 plants also showed higher ABA content, changes in ABA sensitivity, and modified expression of ABA- and stress-regulated genes. While the oxr2 mutants had a similar shoot phenotype to the wild-type, they exhibited increased sensitivity to stress. We propose that by influencing the levels of reactive oxygen species (ROS), AtOXR2 improves the efficiency of photosynthesis and elicits basal tolerance to environmental challenges that increase oxidative stress, allowing improved plant growth and biomass production.

Differential hormonal and gene expression dynamics in two inbred sunflower lines with contrasting dormancy level.

Seed germination and dormancy are tightly regulated by hormone metabolism and signaling pathway. We investigated the endogenous content of abscisic acid (ABA), its catabolites, and gibberellins (GAs), as well as the expression level of certain ABA and GAs metabolic and signaling genes in embryo of dry and imbibed cypselas of inbred sunflower (Helianthus annuus L., Asteraceae) lines: B123 (dormant) and B91 (non-dormant). Under our experimental conditions, the expression of RGL2 gene might be related to the ABA peak in B123 line at 3 h of imbibition. Indeed, RGL2 transcripts are absent in dry and early embedded cypselas of the non-dormant line B91. ABA increase was accompanied by a significant ABA-Glucosyl ester (ABA-GE) and phaseic acid (PA) (two ABA catabolites) decrease in B123 line (3 h) which indicates that ABA metabolism seems to be more active in this line, and that it would be involved in the imposition and maintenance of sunflower seed dormancy, as it has been reported for many species. Finally, an increase of bioactive GAs (GA1 and GA3) occurs at 12 h of imbibition in both lines after a decrease in ABA content. This study shows the first report about the RGL2 tissue-specific gene expression in sunflower inbred lines with contrasting dormancy level. Furthermore, our results provide evidence that ABA and GAs content and differential expression of metabolism and signaling genes would be interacting in seed dormancy regulation through a mechanism of action related to embryo itself.

Early perception of stink bug damage in developing seeds of field-grown soybean induces chemical defences and reduces bug attack.

BACKGROUND: Southern green stink bugs (Nezara viridula L.) invade field-grown soybean crops, where they feed on developing seeds and inject phytotoxic saliva, which causes yield reduction. Although leaf responses to herbivory are well studied, no information is available about the regulation of defences in seeds. RESULTS: This study demonstrated that mitogen-activated protein kinases MPK3, MPK4 and MPK6 are expressed and activated in developing seeds of field-grown soybean and regulate a defensive response after stink bug damage. Although 10-20 min after stink bug feeding on seeds induced the expression of MPK3, MPK6 and MPK4, only MPK6 was phosphorylated after damage. Herbivory induced an early peak of jasmonic acid (JA) accumulation and ethylene (ET) emission after 3 h in developing seeds, whereas salicylic acid (SA) was also induced early, and at increasing levels up to 72 h after damage. Damaged seeds upregulated defensive genes typically modulated by JA/ET or SA, which in turn reduced the activity of digestive enzymes in the gut of stink bugs. Induced seeds were less preferred by stink bugs. CONCLUSION: This study shows that stink bug damage induces seed defences, which is perceived early by MPKs that may activate defence metabolic pathways in developing seeds of field-grown soybean. © 2015 Society of Chemical Industry.

Influence of different test parameters on the microshear bond strength of two simplified etch-and-rinse adhesives.

PURPOSE: To evaluate the effect of different test parameters on the resin-dentin microshear bond strength (µSBS). MATERIALS AND METHODS: A 1.5-mm-thick dentin disk was prepared in each of 140 human molars. The disks were divided into five groups to test the following variables: time of adhesive light polymerization (n = 20), storage time (n = 40), bonding area (n = 40), Tygon tube removal (n = 20), and time of composite placement (n = 20). The adhesives were applied and each specimen was subjected to µSBS testing. All fractured specimens were observed with SEM. The data from each experiment were subjected to two-way ANOVA and Tukey's test (α = 0.05). RESULTS: The storage time, bonding area, and Tygon tube removal did not influence the µSBS. Higher µSBS values were found when empty Tygon tubes were filled after positioning and when the adhesive was light polymerized before Tygon tube placement (p < 0.05). CONCLUSIONS: Differences in test parameters affected the µSBS of adhesives, especially the time of adhesive light polymerization and composite placement.

Do the microshear test variables affect the bond strength values?

Little is known about the effect of specimen preparation and testing protocols on the micro-shear bond strength (µSBS) results. To evaluate whether variations in polyethylene rod use affect (µSBS)). Human dentin disks were randomly distributed into six groups (n = 5): polyethylene tube (3 levels) and adhesive system (2 levels). In Group 1, polyethylene tubes filled with polymerized composite) were placed on adhesive covered surfaces. Tubes were removed 24 h after water storage, leaving the rods only. In Group 2, the same procedure was performed; however, tubes were kept in place during testing. In Group 3, composite rods without tubes were placed on adhesive covered dentin. In all groups, adhesives were photoactivated after positioning filled tubes/rods on adhesive covered surfaces. Specimens were tested under shear mode and the data subjected to a two-way ANOVA and Tukey's tests. Groups 1 and 2 resulted in statistically similar mean µSBS (P > 0.05); however, a greater number of pretest failures were observed for Group 1. Higher µSBS values were detected for Group 3, irrespective of adhesive system used (P < 0.05). Removing the polyethylene tube before composite rod is placed on dentin affects µSBS values.

Avaliação do diagnóstico da leishmaniose visceral canina com a utilização de teste rápido com antígeno recombinante K39 em regiões endêmicas do estado de São Paulo / Assessment of canine visceral leishmaniasis diagnosis by means of a rapid test using recombinant antigen K39 in endemic regions of São Paulo state, Brazil

Em inquéritos caninos, realizados em municípios paulistas com autoctonia de leishmaniose visceral americana (LVA), o desempenho do teste rápido imunocromatográfico (formato “dipstick”) empregando antígeno recombinante K39 (rK39) foi realizado em amostras de sangue total e soro de cães. Este teste foi comparado com a técnica de RIFI e com ELISA as quais foram realizadas em amostras de soro. As amostras foram colhidas de 1.333 cães, sendo 1199 selecionados por sorteio em municípios com transmissão de LVA. O grupo controle foi constituído de amostras de 134 cães portadores de outras patologias ou residentes em áreas indenes para LVA, para avaliar a especificidade do teste rápido antirK39. Nos cães selecionados por sorteio, a positividade do teste rápido anti-rK39 foi de 31,3% nas amostras de soro e de 17,4% no sangue total; a RIFI e o ELISA detectaram anticorpos anti-Leishmania em 25,1% e 27,2% das amostras, respectivamente. Todas amostras do grupo controle apresentaram resultados negativos no teste rápido. O teste rápido realizado em amostras de soro apresenta-se como ensaio simples, rápido, de baixo custo e, portanto, adequado para ser empregado como técnica alternativa de triagem diagnóstica em função de sua especificidade para as espécies do complexo Leishmania donovani, responsáveis pela leishmaniose visceral.

Canine visceral leishmaniasis (CVL) coexists with human visceral leishmaniasis (HVL) in Brazil. Dogs play an important role as reservoir of etiological agent, and for CVL dissemination. For diagnosing CVL, IFA and ELISA have been routinely employed. These assays have not been suitable for diagnosis studies owing to low sensitivity and/or specificity. The CVL diagnosis in different regions of São Paulo was assessed, comparing the performance of a immunochromatographic dipstick – based rapid test using K39 recombinant antigen (rK39RT) on whole blood and serum samples, and with IFI and ELISA on serum samples. The 1,333 samples dogs were tested including 1,199 samples from randomly selected dogs from eight municipalities with CVL transmission. The control group was comprised by samples from 134 animals living VL-free area or from dogs with other diseases. Of 1,199 samples, 31.3% were positive by rK39RT on sera, and 17.4% on whole blood. Anti-Leishmania antibodies were detected in 25.1% and 27.2% of samples on IFA and ELISA, respectively. rK39RT revealed a low performance on whole blood, however on dog serum higher number of positive samples were detected. All samples from 47 dogs with other diseases were negative on rK39RT. The rK39RT is a simple, rapid, inexpensive, specific and sensitive, and suitable as an alternative screening testing.