Improving C4 photosynthesis to increase productivity under optimal and suboptimal conditions.

Although improving photosynthetic efficiency is widely recognized as an underutilized strategy to increase crop yields, research in this area is strongly biased towards species with C3 photosynthesis relative to C4 species. Here, we outline potential strategies for improving C4 photosynthesis to increase yields in crops by reviewing the major bottlenecks limiting the C4 NADP-malic enzyme pathway under optimal and suboptimal conditions. Recent experimental results demonstrate that steady-state C4 photosynthesis under non-stressed conditions can be enhanced by increasing Rubisco content or electron transport capacity, both of which may also stimulate CO2 assimilation at supraoptimal temperatures. Several additional putative bottlenecks for photosynthetic performance under drought, heat, or chilling stress or during photosynthetic induction await further experimental verification. Based on source-sink interactions in maize, sugarcane, and sorghum, alleviating these photosynthetic bottlenecks during establishment and growth of the harvestable parts are likely to improve yield. The expected benefits are also shown to be augmented by the increasing trend in planting density, which increases the impact of photosynthetic source limitation on crop yields

Measuring Rubisco activity: challenges and opportunities of NADH-linked microtiter plate-based and 14C-based assays:NADH-linked and 14C-based assays of Rubisco activity

Rubisco is central to carbon assimilation and efforts to improve the efficiency and sustainability of crop production have spurred interest in phenotyping Rubisco activity. We tested the hypothesis that microtiter plate-based methods provide comparable results to those obtained with the radiometric assay that measures the incorporation of 14CO2 into 3-phosphoglycerate (3-PGA). Three NADH-linked assays were tested that use alternative coupling enzymes: glyceraldehyde-3-phosphate-dehydrogenase and glycerolphosphate-dehydrogenase (GAPDH-GlyPDH); phosphoenolpyruvate-carboxylase and malate-dehydrogenase (PEPC-MDH); pyruvate-kinase and lactate-dehydrogenase (PK-LDH). To date there has been no thorough evaluation of their reliability by comparison with the 14C-based method. The three NADH-linked assays were used in parallel to estimate (1) the 3-PGA concentration response curve of NADH oxidation, (2) the Michaelis-Menten constant for RuBP, (3) fully active and inhibited Rubisco activities, and (4) Rubisco initial and total activities in fully illuminated and shaded leaves. All three methods correlated strongly with the 14C-based method, and the PK-LDH method showed a strong correlation and was the cheapest method. PEPC-MDH would be a suitable option for situations where ADP/ATP might interfere with the assay. GAPDH-GlyPDH proved more laborious than the other methods. Thus, we recommend the PK-LDH as a reliable, cheaper and higher throughput method to phenotype Rubisco activity for crop improvement efforts

Protocols from Sales et al. (2020) Rubisco activity: challenges and opportunities of NADH-linked microtiter plate-based and 14C-based assays

This collection of protocols includes four assays for measuring Rubisco activity that are used and discussed in the manuscript "Rubisco activity: challenges and opportunities of NADH-linked microtiter plate-based and 14C-based assays" (Sales et al. 2020). Three of the protocols are NADH-linked microtiter plate-based assays for Rubisco activity that use alternative coupling enzymes: 1. GAPDH-GlyPDH, glyceraldehyde-3-phosphate-dehydrogenase and glycerolphosphate-dehydrogenase; 2. PEPC-MDH, phosphoenolpyruvate-carboxylase and malate-dehydrogenase; 3. PK-LDH, pyruvate-kinase and lactate-dehydrogenase. The radiometric assay for Rubisco activity measures the incorporation of 14CO2 into 3-phosphoglycerate (3-PGA). The fifth protocol describes the purification of 2,3-bisphosphate-dependent phosphoglycerate mutase (dPGM), which is required for the NADH-linked microtiter plate-based assays 2 (PEPC-MDH) and 3 (PK-LDH)

ESICM LIVES 2016: part two : Milan, Italy. 1-5 October 2016.

Meeting abstrac

Effect of Alirocumab on Mortality After Acute Coronary Syndromes An Analysis of the ODYSSEY OUTCOMES Randomized Clinical Trial

10.1161/CIRCULATIONAHA.118.038840CIRCULATION1402103-11

Risk Categorization Using New American College of Cardiology/American Heart Association Guidelines for Cholesterol Management and Its Relation to Alirocumab Treatment Following Acute Coronary Syndromes

10.1161/CIRCULATIONAHA.119.042551CIRCULATION140191578-158