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Malate dehydrogenase (MDH) is an enzyme that catalyzes the interconversion of malate and oxaloacetate substrates and is widely distributed from prokaryotes to eukaryotes. It plays crucial roles in many important metabolic pathways and includes different isoforms based on coenzyme specificity and cellular localization. To study MDH in rhodophytes, we obtained a full-length cDNA clone (here designated PhMDH) encoding an NAD-malate dehydrogenase in the marine red alga Pyropia haitanensis. The nucleotide sequence of PhMDH was 1521 bp, including an open reading frame (ORF) of 984 bp. The amino acid sequence showed 73% identity with other MDHs in proteobacteria. Two MDH-like domains were detected in the 5-145 and 156-320 regions. Real-time fluorescent quantitative PCR (qPCR) was used to examine mRNA expression levels during the gametophyte and sporophyte phases. The transcription of PhMDH in the gametophyte was barely detectable, whereas PhMDH in the sporophyte showed a much higher expression level. The activity of PhMDH in the filamentous sporophyte was approximately double that of the leafy gametophyte. Considering these results, we suggest that PhMDH may be localized in the cytosol and play a role in carbon fixation in the sporophyte stage. [ABSTRACT FROM AUTHOR]

To characterize the structure and function of the protein phosphatase 2C (PP2C) gene in Porphyra yezoensis, full-length cDNA of the locus (denoted pypp2c) was obtained by electronic cloning, rapid amplification of cDNA ends, and reverse-transcription PCR. The nucleotide sequence of PyPP2C was 1988 bp, including a 5′-untranslated region (UTR) of 301 bp, a 3′-UTR of 256 bp, and an open reading frame of 1431 bp that can be translated into 476 amino acids with a molecular mass of 50.96 kDa and a putative isoelectric point of 8.34. The amino acids had 30-36% identity with those encoded by PP2C genes in protozoa and higher plants. A PP2C-like catalytic domain was found in the 57-397 region, and several residues involved in the metal ion binding sites were conserved. mRNA expression levels in the three life stages of leafy thalli, filaments, and conchospores were examined by real-time fluorescent quantitative PCR. Highest expression of pypp2c occurred in conchospores. Gene expression levels were similar among the three life stages. pypp2c expression at different thallus relative water contents (RWCs) varied, with the highest expression occurring at 60% RWC. [ABSTRACT FROM AUTHOR]