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

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

Optimizing photorespiration for improved crop productivity

© 2018 Institute of Botany, Chinese Academy of Sciences In C3 plants, photorespiration is an energy-expensive process, including the oxygenation of ribulose-1,5-bisphosphate (RuBP) by ribulose 1,5-bisphosphate carboxylase/oxygenase (Rubisco) and the ensuing multi-organellar photorespiratory pathway required to recycle the toxic byproducts and recapture a portion of the fixed carbon. Photorespiration significantly impacts crop productivity through reducing yields in C3 crops by as much as 50% under severe conditions. Thus, reducing the flux through, or improving the efficiency of photorespiration has the potential of large improvements in C3 crop productivity. Here, we review an array of approaches intended to engineer photorespiration in a range of plant systems with the goal of increasing crop productivity. Approaches include optimizing flux through the native photorespiratory pathway, installing non-native alternative photorespiratory pathways, and lowering or even eliminating Rubisco-catalyzed oxygenation of RuBP to reduce substrate entrance into the photorespiratory cycle. Some proposed designs have been successful at the proof of concept level. A plant systems-engineering approach, based on new opportunities available from synthetic biology to implement in silico designs, holds promise for further progress toward delivering more productive crops to farmer\u27s fields

Overexpressing the H-protein of the glycine cleavage system increases biomass yield in glasshouse and field grown transgenic tobacco plants

Photorespiration is essential for C3 plants, enabling oxygenic photosynthesis through the scavenging of 2‐phosphoglycolate. Previous studies have demonstrated that overexpression of the L‐ and H‐proteins of the photorespiratory glycine cleavage system results in an increase in photosynthesis and growth in Arabidopsis thaliana. Here, we present evidence that under controlled environment conditions an increase in biomass is evident in tobacco plants overexpressing the H‐protein. Importantly, the work in this paper provides a clear demonstration of the potential of this manipulation in tobacco grown in field conditions, in two separate seasons. We also demonstrate the importance of targeted overexpression of the H‐protein using the leaf‐specific promoter ST‐LS1. Although increases in the H‐protein driven by this promoter have a positive impact on biomass, higher levels of overexpression of this protein driven by the constitutive CaMV 35S promoter result in a reduction in the growth of the plants. Furthermore in these constitutive overexpressor plants, carbon allocation between soluble carbohydrates and starch is altered, as is the protein lipoylation of the enzymes pyruvate dehydrogenase and alpha‐ketoglutarate complexes. Our data provide a clear demonstration of the positive effects of overexpression of the H‐protein to improve yield under field conditions

Composition, density, and biomass of salpidae and chaetognatha in the southwestern Atlantic Ocean (34.5°S-39°S)

Salps and chaetognaths constitute an important fraction of the macrozooplankton and have a prominent role in the marine food web. In our study, we analyzed the species composition, density, and biomass in an area of the southern Atlantic Ocean during the austral winters of 1999, 2000, and 2001. The most abundant and frequent species were the salpids Ihlea magalhanica (Apstein, 1894) and Iasis zonaria (Pallas, 1774), and the chaetognaths Parasagitta friderici (Ritter-Zahony, 1911) and Serratosagitta tasmanica (Thomson, 1947). Chaetognaths were found in over 80% of the stations throughout the three winters, reaching up to 67 individuals (ind) m -3. Salps were found surviving at low population densities in 2000 and 2001, but in 1999, there were mass occurrences of I. zonaria and I. magalhanica, reaching densities of 301 and 123 ind m -3, respectively. To estimate biomass in C units, the relationship between dry weight and size was calculated for S. tasmanica and for solitaries and aggregates of I. zonaria and I, magalhanica. The biomass of salps and chaetognaths (as mg C m -3) over the shelf during the three consecutive winters was strongly related to prevailing physical and biological conditions. In 1999, the greatest contribution to macrozooplankton biomass corresponded to salps, while in 2000 and 2001, chaetognaths dominated the biomass. In swarm conditions, like in 1999, I. zonaria and I. magalhanica widely dominated over copepods and chaetognaths, producing an increase in the quantity of available C of up to 60 times in relation to the periods with very low population densities.Fil: Daponte, María Cristina. Universidad de Buenos Aires; ArgentinaFil: Calcagno, Javier Angel. Universidad de Buenos Aires; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Acevedo Luque, María José de Jesús. Universidad de Buenos Aires; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Martos, Patricia. Instituto Nacional de Investigaciones y Desarrollo Pesquero; Argentina. Universidad Nacional de Mar del Plata; ArgentinaFil: Machinandiarena, Laura. Universidad Nacional de Mar del Plata; ArgentinaFil: Esnal, Graciela Beatriz. Universidad de Buenos Aires; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin

Nuevas carreras en energías renovables en Uruguay: ingeniería y tecnólogo

La Universidad Tecnológica (UTEC) del Uruguay es una propuesta de educación pública, de perfil tecnológico, que amplía la oferta terciaria universitaria en el interior de Uruguay, fomentando el vínculo con el medio productivo y la promoción del desarrollo social y cultural del país. En 2016 se comienza a dictar la carrera de Ingeniería en Energías Renovables en la ciudad de Durazno. Tiene una duración de diez semestres, donde al sexto se obtiene el título intermedio de Tecnólogo en Energías Renovables (mención Eólica o Solar). La creación de la carrera responde a las necesidades surgidas de la transformación tecnológica que el país viene experimentando de manera rápida y significativa en el área de las energías renovables. Tiene como objeto formar profesionales para implementar y mantener instalaciones de generación de energías renovables, e investigar, con el fin de contribuir al desarrollo futuro del país; con un perfil de egreso basado en competencias.The Technological University of Uruguay (UTEC) is a public education initiative with a technological profile that expands the university offer to the Uruguayan provinces, promoting the link with the industry and the social and cultural development of the country. The Renewable Energy Engineering program was launched in 2016 in the city of Durazno. This university course consists of ten semesters. In the sixth semester the student obtains an intermediate degree as a Renewable Energies Technician (Option: Wind Energy or Solar Energy). The creation of this university program responds to the needs arising from the rapid and significant technological transformation that Uruguay has been experimenting in the field of renewable energies. The aim of the program is to train professionals in the implementation and maintenance of renewable energy generation facilities, and to conduct research in order to contribute to the future development of the country, with a graduate profile based on competencies.Asociación Argentina de Energías Renovables y Medio Ambiente (ASADES

Glyceraldehyde-3-phosphate dehydrogenase subunits A and B are essential to maintain photosynthetic efficiency

In plants, glyceraldehyde-3-phosphate dehydrogenase (GAPDH; EC 1.2.1.12) reversibly converts 1,3-bisphosphoglycerate to glyceraldehyde-3-phosphate coupled with the reduction of NADPH to NADP+. The GAPDH enzyme that functions in the Calvin Benson Cycle is assembled either from four glyceraldehyde-3-phosphate dehydrogenase A subunits (GAPA) proteins forming a homotetramer (A4) or from two GAPA and two glyceraldehyde-3-phosphate dehydrogenase B subunit (GAPB) proteins forming a heterotetramer (A2B2). The relative importance of these two forms of GAPDH in determining the rate of photosynthesis is unknown. To address this question, we measured the photosynthetic rates of Arabidopsis (Arabidopsis thaliana) plants containing reduced amounts of the GAPDH A and B subunits individually and jointly, using T-DNA insertion lines of GAPA and GAPB and transgenic GAPA and GAPB plants with reduced levels of these proteins. Here we show that decreasing the levels of either the A or B subunits decreased the maximum efficiency of CO2 fixation, plant growth, and final biomass. Finally, these data showed that the reduction in GAPA protein to 9% wild-type levels resulted in a 73% decrease in carbon assimilation rates. In contrast, eliminating GAPB protein resulted in a 40% reduction in assimilation rates. This work demonstrates that the GAPA homotetramer can compensate for the loss of GAPB, whereas GAPB alone cannot compensate fully for the loss of the GAPA subunit

Nuevas carreras en energías renovables en Uruguay: ingeniería y tecnólogo

La Universidad Tecnológica (UTEC) del Uruguay es una propuesta de educación pública, de perfil tecnológico, que amplía la oferta terciaria universitaria en el interior de Uruguay, fomentando el vínculo con el medio productivo y la promoción del desarrollo social y cultural del país. En 2016 se comienza a dictar la carrera de Ingeniería en Energías Renovables en la ciudad de Durazno. Tiene una duración de diez semestres, donde al sexto se obtiene el título intermedio de Tecnólogo en Energías Renovables (mención Eólica o Solar). La creación de la carrera responde a las necesidades surgidas de la transformación tecnológica que el país viene experimentando de manera rápida y significativa en el área de las energías renovables. Tiene como objeto formar profesionales para implementar y mantener instalaciones de generación de energías renovables, e investigar, con el fin de contribuir al desarrollo futuro del país; con un perfil de egreso basado en competencias.The Technological University of Uruguay (UTEC) is a public education initiative with a technological profile that expands the university offer to the Uruguayan provinces, promoting the link with the industry and the social and cultural development of the country. The Renewable Energy Engineering program was launched in 2016 in the city of Durazno. This university course consists of ten semesters. In the sixth semester the student obtains an intermediate degree as a Renewable Energies Technician (Option: Wind Energy or Solar Energy). The creation of this university program responds to the needs arising from the rapid and significant technological transformation that Uruguay has been experimenting in the field of renewable energies. The aim of the program is to train professionals in the implementation and maintenance of renewable energy generation facilities, and to conduct research in order to contribute to the future development of the country, with a graduate profile based on competencies.Asociación Argentina de Energías Renovables y Medio Ambiente (ASADES