Long-term non-invasive and continuous measurements of legume nodule activity.

Symbiotic nitrogen fixation is a process of considerable economic, ecological and scientific interest. The central enzyme nitrogenase reduces H(+) alongside N2 , and the evolving H2 allows a continuous and non-invasive in vivo measurement of nitrogenase activity. The objective of this study was to show that an elaborated set-up providing such measurements for periods as long as several weeks will produce specific insight into the nodule activity's dependence on environmental conditions and genotype features. A system was developed that allows the air-proof separation of a root/nodule and a shoot compartment. H2 evolution in the root/nodule compartment can be monitored continuously. Nutrient solution composition, temperature, CO2 concentration and humidity around the shoots can concomitantly be maintained and manipulated. Medicago truncatula plants showed vigorous growth in the system when relying on nitrogen fixation. The set-up was able to provide specific insights into nitrogen fixation. For example, nodule activity depended on the temperature in their surroundings, but not on temperature or light around shoots. Increased temperature around the nodules was able to induce higher nodule activity in darkness versus light around shoots for a period of as long as 8 h. Conditions that affected the N demand of the shoots (ammonium application, Mg or P depletion, super numeric nodules) induced consistent and complex daily rhythms in nodule activity. It was shown that long-term continuous measurements of nodule activity could be useful for revealing special features in mutants and could be of importance when synchronizing nodule harvests for complex analysis of their metabolic status.

An RNA sequencing transcriptome analysis reveals novel insights into molecular aspects of the nitrate impact on the nodule activity of Medicago truncatula.

The mechanism through which nitrate reduces the activity of legume nodules is controversial. The objective of the study was to follow Medicago truncatula nodule activity after nitrate provision continuously and to identify molecular mechanisms, which down-regulate the activity of the nodules. Nodule H2 evolution started to decline after about 4 h of nitrate application. At that point in time, a strong shift in nodule gene expression (RNA sequencing) had occurred (1,120 differentially expressed genes). The most pronounced effect was the down-regulation of 127 genes for nodule-specific cysteine-rich peptides. Various other nodulins were also strongly down-regulated, in particular all the genes for leghemoglobins. In addition, shifts in the expression of genes involved in cellular iron allocation and mitochondrial ATP synthesis were observed. Furthermore, the expression of numerous genes for the formation of proteins and glycoproteins with no obvious function in nodules (e.g. germins, patatin, and thaumatin) was strongly increased. This occurred in conjunction with an up-regulation of genes for proteinase inhibitors, in particular those containing the Kunitz domain. The additionally formed proteins might possibly be involved in reducing nodule oxygen permeability. Between 4 and 28 h of nitrate exposure, a further reduction in nodule activity occurred, and the number of differentially expressed genes almost tripled. In particular, there was a differential expression of genes connected with emerging senescence. It is concluded that nitrate exerts rapid and manifold effects on nitrogenase activity. A certain degree of nitrate tolerance might be achieved when the down-regulatory effect on late nodulins can be alleviated.

Maternal syphilis and accomplishing sexual partner treatment: still a huge gap.

Congenital syphilis (CS) is a preventable epidemic disease for which control is hindered by socioeconomic and health system issues. Inadequately treated maternal syphilis (MaS) commonly has serious adverse obstetric outcomes. This study - which is a cross-sectional study in a Brazilian large urban public Mother and Child hospital, making use of secondary data - evaluated the occurrence of treatment of sexual partners (SP) among women with MaS. The results showed that 771 MaS cases were identified from 2007 to 2014. No information on SP treatment was available in 570 (73.9%) cases. Of the 201 cases presenting information, 25 (12.4%) SP were treated. Out of 164 women having six or more prenatal visits, 25 (15.2%) SP received treatment. Data analyzed biennially have shown a growing trend of cases without collected information, ranging from 27.2% in 2007-2008 to 87.5% in 2013-2014. No linear trend in proportions of treated SP (maximum 7.4% SP treated) was found. Thus, in this study, it has been concluded that the proportion of SP adequately treated was consistently low, and the quality of information deteriorated during the studied period. Prenatal care per se, as provided, was not effective in delivering adequate treatment of SP. Creative integrated services with SP active participation are greatly needed if CS is to be controlled.