Proteomic Analysis of High-CO2-Inducible Extracellular Proteins in the Unicellular Green Alga, Chlamydomonas reinhardtii

Abstract

The unicellular green alga Chlamydomonas reinhardtii can acclimate to a wide range of CO(2) concentrations through the regulation of a CO(2)-concentrating mechanism (CCM). By proteomic analysis, here we identified the proteins which were specifically accumulated under high-CO(2) conditions in a cell wall-less strain of C. reinhardtii which release their extracellular matrix into the medium. When the CO(2) concentration was elevated from the ambient air level to 3% during culture, the algal growth rate increased 1.5-fold and the composition of extracellular proteins, but not intracellular soluble and insoluble proteins, clearly changed. Proteomic analysis data showed that the levels of 22 of 129 extracellular proteins increased for 1 and 3 d and such multiple high-CO(2)-inducible proteins include gametogenesis-related proteins and hydroxyproline-rich glycoproteins. However, we could not prove the induction of gametogenesis under high-CO(2) conditions, suggesting that the inductive signal might be incomplete, not strong enough or that only high-CO(2) conditions might be not sufficient for the cell stage to proceed to the formation of sexually active gametes. However, these gametogenesis-related proteins and/or hydroxyproline-rich glycoproteins may have novel roles outside the cell under high-CO(2) conditions.

Influence of CO2concentration on carbon concentrating mechanisms in cyanobacteria and green algae: a proteomic approach

“…Recently, C. reinhardtii proteome, transcriptome and metabolome have been studied under varying CO 2 concentration. Cumulatively, these studies suggest the involvement of novel transport proteins involved in C i transport and also reveal the effect of induction of CCM on whole genome (Yamano et al 2008, Renberg et al 2010, Baba et al 2011, Fang et al 2012). However, effect of CO 2 on other green alga and cynaobacteria has not been investigated so far.…”

“…Similarly, Fang et al (2012) observed that varying CO 2 concentrations had an effect on 25% of the transcriptome in C. reinhardtii. Proteomic studies on C. reinhardtii under varying concentrations of CO 2 reveal the role of 22 extracellular proteins which are only expressed under low-CO 2 concentration (Baba et al 2011). Similarly, in a transcriptome study, a series of low-CO 2 inducible proteins have Spirulina platensis: exposed sample…”

“…Thus, Ferredoxin-NADP + reductase, which has been identified in proteins spots 9 and 10 from S. platensis proteome (Table 1), is a enzyme involved in the active transportation of HCO 3 -from the external environment for assimilation of CO 2 inside the carboxysomes through the conversion of these HCO 3 -ions by CA (Guedeney et al 1996, Giordano et al 2005). In C. reinhardtii, a variety of CA genes, especially mitochondrial CA, have been implicated for expression only under low-CO 2 condition (Yamano et al 2008, Renberg et al 2010, Baba et al 2011, Fang et al 2012. However, further studies are required to understand whether ferredoxin-NADP + reductase implicated in this study is mitochondrial or membrane bound.…”

Differentially Secreted Proteins of Antarctic and Mesophilic Strains ofSynechocystis SalinaandChlorella Vulgarisafter UV-B and Temperature Stress Treatment

“…cell wall proteome analysis of H. pluvialis and its cell wall mutants identified a subset of induced proteins known to be involved in wall reconstruction and defense (53,54). Baba et al (2) observed remarkable changes in the amount and composition of extracellular proteins after transfer of Chlamydomonas reinhardtii cells to 3 % co 2 . An extracellular cysteine protease inhibitor was purified from culture filtrate of Chlorella sp.…”

“…Briefly, non-boiled protein samples were separated in 12 % acrylamide gels containing 0.1 % gelatin, and after renaturation in 2.5 % triton X-100 solution at room temperature for 30 min, the gel was rinsed with ddh 2 eDtA) before addition of the loading buffer.…”