Large variation in the Rubisco kinetics of diatoms reveals diversity among their carbon-concentrating mechanisms

Abstract

HighlightBroad variations in the CO2 fixation kinetics of diatom Rubisco indicate novel mechanistic diversity and large differences in their carbon-concentrating mechanism.

Diatom Transcriptional and Physiological Responses to Changes in Iron Bioavailability across Ocean Provinces

“…This distinction in both protein structure and transcriptional expression may indicate a distinct adaptation and utilization of RubisCO in the oceanic diatoms than in those from high-Fe coastal waters. Phylogenetically diverse diatom species have been demonstrated to vary in their RubisCO enzyme kinetics in laboratory cultures, with their RubisCO content inversely linked to the strength of their carbon concentrating mechanism (CCM; Young et al, 2016). The CCM increases CO 2 concentrations in chloroplast stroma in the vicinity of RubisCO and is fueled by the energy (ATP) generated from the Fe-intensive process of photosynthesis (Reinfelder, 2011;Young et al, 2016).…”

“…Phylogenetically diverse diatom species have been demonstrated to vary in their RubisCO enzyme kinetics in laboratory cultures, with their RubisCO content inversely linked to the strength of their carbon concentrating mechanism (CCM; Young et al, 2016). The CCM increases CO 2 concentrations in chloroplast stroma in the vicinity of RubisCO and is fueled by the energy (ATP) generated from the Fe-intensive process of photosynthesis (Reinfelder, 2011;Young et al, 2016). We hypothesize that chronically Fe-limited oceanic diatoms are ATP-limited by the scarcity of Fe needed to support photosynthesis, and instead increase their RubisCO protein content to maintain high rates of carbon fixation rather than allocate scarce energy resources to the CCM.…”

Interactive effects of nitrogen and light on growth rates and RUBISCO content of small and large centric diatoms

“…Thus, the low performance of RUBISCO turnover rate in our larger diatoms in (Wu et al 2014b) was not attributable to luxury accumulation of excess RUBISCO, but rather to a limitation on their growth rates under high concentrations of NO 3 − in typical laboratory media. These differences between studies illustrate the complexities of macromolecular allocations to cellular functions across strains and growth conditions (Young et al 2016). The different L:D cycles between (Wu et al 2014a) (12:12 L:D) and herein (24:0 L:D) could also contribute to the differences between the studies as shorter photoperiods increase the achieved RUBISCO turnover rate, particularly for larger diatoms (Li and Campbell, unpubl.…”

“…1a). There are two main strategies for phytoplankton to maintain growth rate when the growth environment is not favorable, to increase the abundance of rate-limiting enzymes or to increase the achieved enzymatic rates, as shown in particular by studies of the enzyme responsible for carbon fixation, RUBISCO (Feller and Gerday 2003; Young et al 2015, 2016). Phytoplankton can thus allocate an increased fraction of their cellular N to growth rate-limiting enzymes, as for example RUBISCO, to maintain their growth when the media N source is low, consistent with our results for T. pseudonana grown at low growth light (Fig.…”

Characterization of the heterooligomeric red-type rubisco activase from red algae

“…Rubisco from a number of species formed inhibited complexes of varying stability with RuBP (21), but in more detailed work, the enzyme from the red algae Galdieria sulphuraria was reported to exhibit high inhibition constants (22). Low rubisco activation states in rapidly extracted soluble lysates from various diatom species have been reported, suggesting the requirement for an activase (23,24). Understanding and defining the activase requirement of eukaryotic red-type rubiscos is especially pertinent, because a number of these enzymes have been demonstrated to possess kinetic properties (such has high CO 2 /O 2 specificity factors) that would confer enhanced photosynthetic properties to land Significance Eukaryotic phytoplankton of the red plastid lineage dominate the oceans and are responsible for a significant proportion of global photosynthetic CO 2 fixation.…”