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Hybrid CCM in Thalassiosira pseudonana

ABSTRACT: Manipulated carbonate chemistry to disentangle proteins involved in the carbon concentrating mechanism (CCM) of Thalassiosira pseudonana from other cellular mechanisms that employ the same proteins. The malate/oxaloacetate shuttle shares overlap with biochemical CCMs while also supporting pH regulation, maintenance of redox poise, cyclic electron transport, and the dissipation of excess light energy. Three treatments were used to separate out the effects of pH and pCO2: low pCO2/high pH (LCHpH), high pCO2/low pH (HCLpH), and low pCO2/low pH (LCLpH). Results from this analysis were consistent with a hybrid CCM within T. pseudonana that consists of both biophysical and biochemical steps. No evidence for alternative cellular mechanisms that could explain protein abundance profiles observed under low pCO2 conditions was found.

INSTRUMENT(S):

ORGANISM(S): Thalassiosira Pseudonana Ccmp1335

TISSUE(S): Plant Cell, Photosynthetic Cell, Cell Culture

SUBMITTER: Anthony Himes

LAB HEAD: Adam Kustka

PROVIDER: PXD064793 | Pride | 2025-10-13

REPOSITORIES: Pride

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Project description:Diatoms are responsible for ~40% of marine primary productivity1, fueling the oceanic carbon cycle and contributing to natural carbon sequestration in the deep ocean2. Diatoms rely on energetically expensive carbon concentrating mechanisms (CCMs) to fix carbon efficiently at modern levels of CO23–5. How diatoms may respond over the short and long-term to rising atmospheric CO2 remains an open question. Here we use nitrate-limited chemostats to show that the model diatom Thalassiosira pseudonana rapidly responds to increasing CO2 by differentially expressing gene clusters that regulate transcription and chromosome folding and subsequently reduces transcription of photosynthesis and respiration gene clusters under steady-state elevated CO2. These results suggest that exposure to elevated CO2 first causes a shift in regulation and then a metabolic rearrangement. Genes in one CO2-responsive cluster included CCM and photorespiration genes that share a putative cyclic-AMP responsive cis-regulatory sequence, implying these genes are co-regulated in response to CO2 with cAMP as an intermediate messenger. We verified cAMP-induced down-regulation of CCM gene ?-CA3 in nutrient-replete diatom cultures by inhibiting the hydrolysis of cAMP. These results indicate an important role for cAMP in down-regulating CCM and photorespiration genes under elevated CO2 and provide insights into mechanisms of diatom acclimation in response to climate change. In steady-state experiments: axenic T. pseudonana cells in four biological replicates (duplicate chemostats x 2 experimental runs) were acclimated to nitrate-limitation at 70% (1.5 day-1) of max growth rate for >10 days (>15 generations) under continuous light of 80 µmol photons·m?2·s?1. Cell biomass was maintained at ~2 x 105 cells·mL?1 by 10 ?M nitrate and carbonate chemistry stabilized to 300, 475 or 800 ?atm CO2, verified by pH and DIC measurements. Transition samples and carbonate chemistry were collected daily from chemostat cultures as CO2 levels were increased from ~300-800 ?atm at a rate ? 0.2 ?atm·min?1 over four consecutive days (6 generations) after pre-acclimation to 300 ?atm CO2 and nitrate-limitation.

			Action	DRS
	0602_Universal_Contaminants.fasta	Fasta
	Curated_Tp_ref_library.fasta	Fasta
	ECL09145.raw	Raw
	ECL09146.raw	Raw
	ECL09147.raw	Raw

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Hybrid CCM in Thalassiosira pseudonana

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