A tomato alternative oxidase protein with altered regulatory properties

• Published in: Biochimica et biophysica acta Vol. 1606; no. 1; pp. 153 - 162
• Main Authors: Holtzapffel, Ruth C, Castelli, Joanne, Finnegan, Patrick M, Millar, A.Harvey, Whelan, Jim, Day, David A
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 30.09.2003
• Subjects: Alternative oxidase; alternative oxidases; Amino Acid Sequence; Base Sequence; Cold Temperature; Diagonal PAGE; DNA Primers; Gene Expression Regulation, Enzymologic; Gene Expression Regulation, Plant; Genome, Plant; Isoenzymes - genetics; Isoenzymes - isolation & purification; Isoenzymes - metabolism; isozymes; Lycopersicon esculentum - enzymology; Mitochondria; Mitochondrial Proteins; Molecular Sequence Data; Multigene Family; oxidoreductases; Oxidoreductases - genetics; Oxidoreductases - isolation & purification; Oxidoreductases - metabolism; Plant Proteins - genetics; Plant Proteins - isolation & purification; Plant Proteins - metabolism; Polymerase Chain Reaction; Recombinant Proteins - isolation & purification; Recombinant Proteins - metabolism; Sequence Alignment; Sequence Homology, Amino Acid; Solanum lycopersicum var. lycopersicum; Tomato; tomatoes; Transcription, Genetic; Mitochondria; Alternative oxidase; Tomato; Diagonal PAGE
• ISSN: 0005-2728; 0006-3002; 1879-2650
• DOI: 10.1016/S0005-2728(03)00112-9

We have investigated the expression and regulatory properties of the two alternative oxidase (Aox) proteins that are expressed in tomato ( Lycopersicon esculentum L. Mill cv. Sweetie) after storage of green fruit at 4 °C. Four Aox genes were identified in the tomato genome, of which two ( LeAox1a and LeAox1b) were demonstrated to be expressed in cold-treated fruit. The activity and regulatory properties of LeAox1a and LeAox1b were assayed after expression of each protein in yeast cells ( Saccharomyces cerevisiae), proving that each is an active Aox protein. The LeAox1b protein was shown to have altered regulatory properties due to the substitution of a Ser for the highly conserved Cys I residue. LeAox1b could not form inactive disulfide-linked dimers and was activated by succinate instead of pyruvate. This is the first example of a dicot species expressing a natural Cys I/Ser isoform. The implications of the existence and expression of such Aox isoforms is discussed in the light of the hypothesised role for Aox in plant metabolism.