The Moderating Effects of Family Management Factors on the Relationship between Violence Exposure and Aggression

Community violence, in the form of direct victimization or witnessing violent acts, is a prevalent public safety concern in many communities. Individuals who are exposed to community violence often exhibit a variety of associated mental health concerns, including anxiety, depression, and posttraumatic stress symptoms. One of the most common negative outcomes associated with violence exposure among adolescents is engaging in aggressive or violent behavior. In order to mitigate the health, safety, and legal consequences associated with this outcome, it is worth examining factors that may protect adolescents from exhibiting behavior problems subsequent to community violence exposure. In the present study, family management factors (i.e., family routines, disciplinary practices, and monitoring/supervision) were investigated as potential moderating factors in the relationship between violence exposure and adolescent aggression. Community violence exposure, along with two family management variables (i.e., poor parental monitoring and inconsistent discipline), significantly predicted aggressive behavior. Family management factors were insignificant as moderators of the relationship between community violence exposure and aggression. This pattern of results suggests that the specific parenting practices examined are general “protective” factors for adolescents, as they appear beneficial for reducing negative behavioral outcomes regardless of the context of risk

JXB at SEB Florence 2018

SEB Annual Meetings cover a diverse range of plant, animal and cell biology, and that diversity extends within each section as scientists we are all specialists, but we all deeply value the wider connections between disciplines that are a vital part of the organization. That range and ethos is echoed in the plant science published in Journal of Experimental Botany (JXB) every month, and this year we have put together a virtual issue of the journal both to celebrate our approach and increase awareness of how the content is developing

Improving plant productivity by re‐tuning the regeneration of RuBP in the Calvin Benson Bassham Cycle

The Calvin–Benson–Bassham (CBB) cycle is arguably the most important pathway on earth, capturing CO2 from the atmosphere and converting it into organic molecules, providing the basis for life on our planet. This cycle has been intensively studied over the 50 yr since it was elucidated, and it is highly conserved across nature, from cyanobacteria to the largest of our land plants. Eight out of the 11 enzymes in this cycle catalyse the regeneration of ribulose-1-5 bisphosphate (RuBP), the CO2 acceptor molecule. The potential to manipulate RuBP regeneration to improve photosynthesis has been demonstrated in a number of plant species, and the development of new technologies, such as omics and synthetic biology provides exciting future opportunities to improve photosynthesis and increase crop yields

Comparison of the effects of trypsin and chymotrypsin on thylakoid membrane function

The thylakoid membranes are the functional units upon which the photosynthetic energy-tansducing reactions occur. There is a strict relationship between the structure of these membranes and their functional capabilities; this is because the components of the photosynthetic electron-transport chain are bound to proteins in the membrane in a specific manner. Functional changes can be induced by using protediytic enzymes to alter the structure of the proteins. Two enzymes, trypsin (which digests bonds involving arginine and lysine) and chymotrypsin (which digest bonds involving tryptophan, tryosine and phenylalanine) have been used to investigate the functions of the thylakoid membrane. The rationale was that because these enzymes have different specificities for the bonds which they attack they may induce different functional changes in the membrane. The effects of these enzymes are compared. Measurements of light-induced oxygen evolution rates in the presence of exogenous electron acceptors showed that both trypsin and chymotrypsin altered the electron transport reactions in a number of ways. At higher concentrations both trypsin and chymotrypsin treatment of thylakoids caused the rate of electron transport to be dependent on the type of electron acceptor present and rendered electron transport insensitive to 3-(3,4-dichlorophenyl)-1,1-dimethylurea which inhibits photosystem II. These effects of trypsin have previously been shown to be due to partial digestion of a 32KDa protein on the acceptor side of photosystem II. Thus chymotrypsin may also affect this polypeptide. At lower concentrations trypsin, and to a lesser extent chymotrypsin, stimulated the rate of electron transport. This suggested that both of these enzymes tend to uncouple the thylakoid membranes. Trypsin and chymotrypsin altered the flash-induced field indicating absorption change measured at 520 nm (the electrochromic bandshift) in two ways : 1) the half-time of decay was decreased suggesting increased trans-membrane ion flux and 2) the extent was reduced. The decrease in the half-time of the decay of the electrochromic bandshift was correlated with uncoupling, by trypsin and to a lesser extent by chymotrypsin, of the thylakoid membrane. This proposal was supported by phosphorylation measurements which showed that both trypsin and chymotrypsin can, at least partially, inhibit ATP synthesis. But after brief trypsin incubation in the light a stimulation in the rate of phosphorylation and oxygen evolution (water to methyl viologen) was evident. It is possible that trypsin affects the e sub-unit, believed to be an inhibitor of ATPase function, however, no evidence to support this proposal was seen in polyacrylamide gel electrophoresis analysis of the ATPase. (Abstract shortened by ProQuest.)

Over-expressing the C3 photosynthesis cycle enzyme Sedoheptulose-1-7 Bisphosphatase improves photosynthetic carbon gain and yield under fully open air CO2fumigation (FACE)

Abstract Background Biochemical models predict that photosynthesis in C3 plants is most frequently limited by the slower of two processes, the maximum capacity of the enzyme Rubisco to carboxylate RuBP (Vc,max), or the regeneration of RuBP via electron transport (J). At current atmospheric [CO2] levels Rubisco is not saturated; consequently, elevating [CO2] increases the velocity of carboxylation and inhibits the competing oxygenation reaction which is also catalyzed by Rubisco. In the future, leaf photosynthesis (A) should be increasingly limited by RuBP regeneration, as [CO2] is predicted to exceed 550 ppm by 2050. The C3 cycle enzyme sedoheptulose-1,7 bisphosphatase (SBPase, EC 3.1.3.17) has been shown to exert strong metabolic control over RuBP regeneration at light saturation. Results We tested the hypothesis that tobacco transformed to overexpressing SBPase will exhibit greater stimulation of A than wild type (WT) tobacco when grown under field conditions at elevated [CO2] (585 ppm) under fully open air fumigation. Growth under elevated [CO2] stimulated instantaneous A and the diurnal photosynthetic integral (A') more in transformants than WT. There was evidence of photosynthetic acclimation to elevated [CO2] via downregulation of Vc,max in both WT and transformants. Nevertheless, greater carbon assimilation and electron transport rates (J and Jmax) for transformants led to greater yield increases than WT at elevated [CO2] compared to ambient grown plants. Conclusion These results provide proof of concept that increasing content and activity of a single photosynthesis enzyme can enhance carbon assimilation and yield of C3 crops grown at [CO2] expected by the middle of the 21st century. </jats:sec

The CP12 protein family: a thioredoxin-mediated metabolic switch?

CP12 is a small, redox-sensitive protein, representatives of which are found in most photosynthetic organisms, including cyanobacteria, diatoms, red and green algae, and higher plants. The only clearly defined function for CP12 in any organism is in the thioredoxin-mediated regulation of the Calvin-Benson cycle. CP12 mediates the formation of a complex between glyceraldehyde-3-phosphate dehydrogenase (GAPDH) and phosphoribulokinase (PRK) in response to changes in light intensity. Under low light, the formation of the GAPDH/PRK/CP12 complex results in a reduction in the activity of both PRK and GAPDH and, under high light conditions, thioredoxin mediates the disassociation of the complex resulting in an increase in both GAPDH and PRK activity. Although the role of CP12 in the redox-mediated formation of the GAPDH/PRK/CP12 multiprotein complex has been clearly demonstrated, a number of studies now provide evidence that the CP12 proteins may play a wider role. In Arabidopsis thaliana CP12 is expressed in a range of tissue including roots, flowers, and seeds and antisense suppression of tobacco CP12 disrupts metabolism and impacts on growth and development. Furthermore, in addition to the higher plant genomes which encode up to three forms of CP12, analysis of cyanobacterial genomes has revealed that, not only are there multiple forms of the CP12 protein, but that in these organisms CP12 is also found fused to cystathionine-β-synthase domain containing proteins. In this review we present the latest information on the CP12 protein family and explore the possibility that CP12 proteins form part of a redox-mediated metabolic switch, allowing organisms to respond to rapid changes in the external environment. © 2014 López-Calcagno, Howard and Raines

Overexpression of the RieskeFeS protein increasese electron transport rates and biomass yield

In this study, we generated transgenic Arabidopsis (Arabidopsis thaliana) plants overexpressing the Rieske FeS protein (PetC), a component of the cytochrome b6f (cyt b6f) complex. Increasing the levels of this protein resulted in concomitant increases in the levels of cyt f (PetA) and cyt b6 (PetB), core proteins of the cyt b6f complex. Interestingly, an increase in the levels of proteins in both the photosystem I (PSI) and PSII complexes also was seen in the Rieske FeS overexpression plants. Although the mechanisms leading to these changes remain to be identified, the transgenic plants presented here provide novel tools to explore this. Importantly, overexpression of the Rieske FeS protein resulted in substantial and significant impacts on the quantum efficiency of PSI and PSII,electron transport, biomass, and seed yield in Arabidopsis plants. These results demonstrate the potential for manipulating electron transport processes to increase crop productivity

Feeding the world: improving photosynthetic efficiency for sustainable crop production

A number of recent studies have provided strong support demonstrating that improving the photosynthetic processes through genetic engineering can provide an avenue to improve yield potential. The major focus of this review is on improvement of the Calvin–Benson cycle and electron transport. Consideration is also given to how altering regulatory process may provide an additional route to increase photosynthetic efficiency. Here we summarize some of the recent successes that have been observed through genetic manipulation of photosynthesis, showing that, in both the glasshouse and the field, yield can be increased by >40%. These results provide a clear demonstration of the potential for increasing yield through improvements in photosynthesis. In the final section, we consider the need to stack improvement in photosynthetic traits with traits that target the yield gap in order to provide robust germplasm for different crops across the globe

Arabidopsis CP12 mutants have reduced levels of phosphoribulokinase and impaired function of the Calvin–Benson cycle

CP12 is a small, redox-sensitive protein, the most detailed understanding of which is the thioredoxin-mediated regulation of the Calvin–Benson cycle, where it facilitates the formation of a complex between glyceraldehyde-3-phosphate dehydrogenase (GAPDH) and phosphoribulokinase (PRK) in response to changes in light intensity. In most organisms, CP12 proteins are encoded by small multigene families, where the importance of each individual CP12 gene in vivo has not yet been reported. We used Arabidopsis thaliana T-DNA mutants and RNAi transgenic lines with reduced levels of CP12 transcript to determine the relative importance of each of the CP12 genes. We found that single cp12-1, cp12-2, and cp12-3 mutants do not develop a severe photosynthetic or growth phenotype. In contrast, reductions of both CP12-1 and CP12-2 transcripts lead to reductions in photosynthetic capacity and to slower growth and reduced seed yield. No clear phenotype for CP12-3 was evident. Additionally, the levels of PRK protein are reduced in the cp12-1, cp12-1/2, and multiple mutants. Our results suggest that there is functional redundancy between CP12-1 and CP12-2 in Arabidopsis where these proteins have a role in determining the level of PRK in mature leaves and hence photosynthetic capacity

Multigene manipulation of photosynthetic carbon assimilation increases CO2 fixation and biomass yield in tobacco

Over the next 40 years it has been estimated that a 50% increase in the yield of grain crops such as wheat and rice will be required to meet the food and fuel demands of the increasing world population. Transgenic tobacco plants have been generated with altered combinations of sedoheptulose-1,7-bisphosphatase, fructose-1,6-bisphosphate aldolase, and the cyanobacterial putative-inorganic carbon transporter B, ictB, of which have all been identified as targets to improve photosynthesis based on empirical studies. It is shown here that increasing the levels of the three proteins individually significantly increases the rate of photosynthetic carbon assimilation, leaf area, and biomass yield. Furthermore, the daily integrated measurements of photosynthesis showed that mature plants fixed between 12-19% more CO2 than the equivalent wild-type plants. Further enhancement of photosynthesis and yield was observed when sedoheptulose-1,7-bisphosphatase, fructose-1,6-bisphosphate aldolase, and ictB were over-expressed together in the same plant. These results demonstrate the potential for the manipulation of photosynthesis, using multigene-stacking approaches, to increase crop yields