High ribulose-1,5-bisphosphate carboxylase/oxygenase content in northern diatom species

Abstract

Ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBisCO) is a fundamental enzyme in CO2-fixation in photoautotrophic organisms. Nonetheless, it has been recently suggested that the contribution of this enzyme to total cellular protein is low in phytoplankton, including diatoms (< 6%). Here we show that RuBisCO content is high in some diatom species isolated from northern waters (> 69°N). Two species contained the highest RuBisCO levels ever reported for phytoplankton (36% of total protein). These high RuBisCO requirements do not increase these species’ requirements for nitrogen and do not impart a fitness disadvantage in terms of growth rate. On the contrary, high RuBisCO levels in psychrophilic diatoms may be a necessary mechanism to maintain high growth rates at low temperature at which enzymatic rates are low.

Genome-Scale Metabolic Reconstruction and in Silico Perturbation Analysis of the Polar Diatom Fragilariopsis cylindrus Predicts High Metabolic Robustness

“…We used a GSM of Phaeodactylum tricornutum (iLB1025), which was developed by Levering et al [14] and updated by Broddrick et al [15], as a template for the metabolic model of Fragilariopsis cylindrus (CCMP1102). BlastP analyses revealed that 93.6% of proteins in the P. tricornutum model (see supplementary excel Table Supp1 for a list of the proteins for which we did not find significant Biology 2020, 9,30 3 of 20 homology in the F. cylindrus genome) have significant homologous proteins in the F. cylindrus genome using an E cut-off <0.1 and overall identity >20%. In 39% (26 protein IDs and their associated protein names from the list shown in supplementary excel Table Supp1) of cases when we did not identify significant homologous proteins, it was due to the presence of incomplete sequences caused by genome sequencing gaps in either the P. tricornutum or F. cylindrus genome sequence.…”

“…Living in the polar seas requires specific adaptations and acclimation strategies including cold-adapted enzymes, changes in membrane lipid composition, and antifreeze proteins [5][6][7]. Polar diatoms also have a higher protein content (e.g., rubisco) than temperate diatoms, which allow them to partially compensate for the low catalytic rate at low temperature [8,9], and they are enriched in polyunsaturated fatty acids and carotenoids [7,10]. Polar diatoms generally grow at lower rates than their temperate counterparts, and they exhibit low light saturation parameters for photosynthesis [11].…”

“…Biology 2020,9,30 8 of 20 Biology 2020, 9, x FOR PEER REVIEW 8 of Local sensitivity analysis of the model output (growth rate) to an increase (red bars) or decrease (blue bars) by an arbitrary factor of 40% for each of the 69 model parameters taken independently. The percentage of variation of the growth rate is given on the y-axis (on a log scale) as a function of changes in parameter values (see…”

Photosynthetic Light Reactions in Diatoms. II. The Dynamic Regulation of the Various Light Reactions

“…The combined effects of light with temperature, nutrient availability, and ocean acidification on the regulation of photosynthesis in polar diatoms have been recently extensively considered (Petrou et al 2016;Trimborn et al 2017;Hoppe et al 2018;Lewis et al 2019;Strzepek et al 2019;Yan et al 2019). In general, polar diatoms show photoadaptive features of very low light and temperature acclimation, for instance: i) specific features of Rubisco activity (Valegård et al 2018) including a high cellular Rubisco content Gerecht et al 2019) to compensate for the slow enzymatic rate, ii) very active AEF processes (Alderkamp et al 2012;Goldman et al 2015;Schuback et al 2015;Trimborn et al 2019), iii) the ability to repair damaged PSII even below 0°C (Petrou et al 2010), and iv) a strong antioxidant activity (mycosporine-like amino acids and ROS scavengers (Hernando et al 2002;Janknegt et al 2008;Ha et al 2016)).…”

It's what's inside that matters: physiological adaptations of high‐latitude marine microalgae to environmental change

“…Specific growth rates of 0.5 d À1 are common and some psychrophilic diatoms reach rates of 1.1 d À1 (Zhang et al, 1999;Søgaard et al, 2011;Trimborn et al, 2019). Antarctic and Arctic diatoms compensate for slow catalytic rates by upregulating cellular Rubisco content (Gerecht et al, 2019) (Fig. 3), with estimates of up to 8% of dry weight, compared to only 0.6% in temperate species (Young et al, 2015a).…”