Molecular characterization of low-temperature-inducible NTR-C in Chlorella vulgaris

Abstract

We isolated a cDNA corresponding to a chloroplast NADPH-dependent thioredoxin reductase gene (NTR-C), in Chlorella that is low-temperature-inducible. The obtained cDNA was 1,838 bp in length and coded for 529 amino acids. The deduced amino acid sequence showed higher homology to those of Arabidopsis and rice NTR-C, containing a thioredoxin (Trx) and a thioredoxin reductase (TR), than those of NTR-A (mitochondrial) and NTR-B (cytosolic) from various organisms, which contain only a TR domain and differ in subcellular localization. The results of enzyme assays of partially-purified mature NTR-C protein (mNTR-C), expressed in Escherichia coli with a pET-29b(+) expression vector, provided evidence that the gene included both regions. Northern blot analysis showed a remarkable increase in transcripts under low temperature, while the protein level did not significantly change when examined by using Western blotting with anti-mNTR-C antibodies. The TR activity dependent on NADPH was not enhanced by low temperature despite the substantial increase in transcripts. Based on the results of measurement of peroxiredoxin (Prx) activity and Western blotting using both an extract of Chlorella and purified mNTR-C, the Chlorella was suggested to possess a Prx that interacts with NTR-C.

Thioredoxin Reductase Type C (NTRC) Orchestrates Enhanced Thermotolerance to Arabidopsis by Its Redox-Dependent Holdase Chaperone Function

“…This fusion of domains in NTRC has been verified as an efficient electron donor to 2Cys-Prx (Moon et al, 2006;Pérez-Ruiz et al, 2006). Genes encoding the NTRC have been identified in many photosynthetic organisms including Arabidopsis (Arabidopsis thaliana), rice (Oryza sativa), barrel medic (Medicago truncatula), barley (Hordeum vulgare), and also cyanobacteria but not from non-photosynthetic organisms (Serrato et al, 2004;Pérez-Ruiz et al, 2006;Alkhalfioui et al, 2007;Machida et al, 2007;Pascual et al, 2011;Wulff et al, 2011). Hence, NTRC appears to have originated in cyanobacteria with a transfer of the gene into the genome of eukaryotic cells during the early evolution of chloroplasts.…”

The Quaternary Structure of NADPH Thioredoxin Reductase C Is Redox-Sensitive

“…Recently, a new type of NADPH thioredoxin reductase (NTR), stated NTRC, was described (Serrato et al, 2002(Serrato et al, , 2004. This enzyme is exclusive of oxygenic photosynthetic organisms including some, not all, cyanobacteria (Serrato et al, 2004), green algae (Machida et al, 2007), and plants (Serrato et al, 2004;Moon et al, 2006;Alkhalfioui et al, 2007), where it is localized in chloroplasts. The enzyme is formed by two well defined modules, NTR at the N-terminus and TRX at the C-terminus, both activities being conjugated to reduce 2-Cys PRX and act as a high-efficiency system for hydrogen peroxide reduction in the chloroplast (Pe ´rez-Ruiz et al, 2006).…”

A Comparative Analysis of the NADPH Thioredoxin Reductase C-2-Cys Peroxiredoxin System from Plants and Cyanobacteria

“…2). Therefore, the cyanobacterial enzyme is highly similar to the eukaryotic counterparts, such as the enzymes from rice (Serrato et al, 2004) or the green alga Chlorella (Machida et al, 2007). It should be noted that the full-length AnabNTRC showed a higher rate of NADPH-dependent reduction of DTNB than the truncated NTR domain of the enzyme (Fig.…”