New horizons for building pyrenoid-based CO2-concentrating mechanisms in plants to improve yields.

Many photosynthetic species have evolved CO2-concentrating mechanisms (CCMs) to improve the efficiency of CO2 assimilation by Rubisco and reduce the negative impacts of photorespiration. However, the majority of plants (i.e. C3 plants) lack an active CCM. Thus, engineering a functional heterologous CCM into important C3 crops, such as rice (Oryza sativa) and wheat (Triticum aestivum), has become a key strategic ambition to enhance yield potential. Here, we review recent advances in our understanding of the pyrenoid-based CCM in the model green alga Chlamydomonas reinhardtii and engineering progress in C3 plants. We also discuss recent modeling work that has provided insights into the potential advantages of Rubisco condensation within the pyrenoid and the energetic costs of the Chlamydomonas CCM, which, together, will help to better guide future engineering approaches. Key findings include the potential benefits of Rubisco condensation for carboxylation efficiency and the need for a diffusional barrier around the pyrenoid matrix. We discuss a minimal set of components for the CCM to function and that active bicarbonate import into the chloroplast stroma may not be necessary for a functional pyrenoid-based CCM in planta. Thus, the roadmap for building a pyrenoid-based CCM into plant chloroplasts to enhance the efficiency of photosynthesis now appears clearer with new challenges and opportunities.

The small subunit of Rubisco and its potential as an engineering target.

Rubisco catalyses the first rate-limiting step in CO2 fixation and is responsible for the vast majority of organic carbon present in the biosphere. The function and regulation of Rubisco remain an important research topic and a longstanding engineering target to enhance the efficiency of photosynthesis for agriculture and green biotechnology. The most abundant form of Rubisco (Form I) consists of eight large and eight small subunits, and is found in all plants, algae, cyanobacteria, and most phototrophic and chemolithoautotrophic proteobacteria. Although the active sites of Rubisco are located on the large subunits, expression of the small subunit regulates the size of the Rubisco pool in plants and can influence the overall catalytic efficiency of the Rubisco complex. The small subunit is now receiving increasing attention as a potential engineering target to improve the performance of Rubisco. Here we review our current understanding of the role of the small subunit and our growing capacity to explore its potential to modulate Rubisco catalysis using engineering biology approaches.

Role of small-sized phytoplankton in triggering an ecosystem disruptive algal bloom in a Mediterranean hypersaline coastal lagoon.

Monthly samplings carried out in 2016-2019 and satellite color images from 2002 to 2019 have been combined to determine the onset and causative species of the ecosystem disruptive algal bloom (EDAB) that affects the Mar Menor coastal lagoon (Western Mediterranean Sea) since 2015. Substantial changes in satellite spectral reflectance attributable to increasing abundance of Synechococcus were registered in 2014. Furthermore, cell abundances of this species in 2016 were the largest ever obtained in the lagoon (6 106 cells mL-1), with values similar to those reported for other Mediterranean hypertrophic estuaries and coastal lagoons. These results suggest that the early changes leading to the EDAB started in 2014 and that Synechococcus played a relevant role in its development. Moreover, diatom and dinoflagellate abundances changed substantially in 2016-2019, ranging from 102 to more than 104 cells mL-1. Some of these changes were linked to flood, suggesting that EDAB has modified substantially the homeostatic capacity of the lagoon.

Minimally invasive polyaxial locking plate osteosynthesis for 3-4 part proximal humeral fractures: our institutional experience.

INTRODUCTION: The objectives of this study were to describe the surgical technique of fixation of 3-4 part proximal humeral fractures with polyaxial locking plates utilising a minimally invasive approach and to evaluate the accuracy of reduction and stability of fixation. PATIENTS AND METHODS: We retrospectively reviewed 90 patients. Fractures were classified according to the Neer classification system. Different radiological parameters were measured to assess the quality of reduction and the stability of fixation. Complications and clinical outcomes were evaluated after one year of minimum follow up. RESULTS: There were 76 women and 14 men, with a mean age of 67.4years ±13 (range, 29-85). There were 60 3-part and 30 4-part fractures. Frozen cancellous allograft was used in 30 cases (33.3%). All fractures progressed to union and at one year follow up, the mean Constant score was 79.6±12(range, 62-100). Mean forward flexion, abduction, external rotation and internal rotation were 155°, 148°, 39° and vertebra Dorsal 8, respectively. Complications were noted in seven patients while the postoperative "head-diaphysis angle", "greater tuberosity height" and "medial metaphysis reconstruction" were close to the anatomical parameters; no significant differences were noted at one year radiological follow up. CONCLUSION: Reliable and stable fixation can be expected with the use of polyaxial locking plate through a minimally invasive approach for the treatment of 3-4 part proximal humeral fractures. Satisfactory functional results for this procedure can be obtained.