A comparison of proteins from the developing xylem of compression and non-compression wood of branches of sitka spruce (Picea sitchensis) reveals a differentially expressed laccase.
Soluble and cell wall-associated proteins were extracted from the developing xylem of the compression and non-compression sides of branches of Sitka spruce (Picea sitchensis (Bong) Carr.) by an identical procedure. Equal amounts of proteins were separated by SDS-PAGE, and polypeptides were identified that were more abundant in soluble and cell wall-associated extracts from the developing xylem of either compression or non-compression wood. Two polypeptides (at apparent M(r)s of 48 kDa and 120 kDa) that were more abundant in cell wall-associated extracts of the developing xylem of the compression tissues were selected for amino-terminal protein sequencing. The 48 kDa polypeptide yielded an amino-terminal sequence that had no homology with known protein, gene or EST database sequences. The amino-terminal sequence of the 120 kDa polypeptide was homologous to a number of laccase-type polyphenol oxidases (EC 1.10.3.2) thought to be involved in lignin biosynthesis in trees. Using non-denaturing SDS-PAGE, the 120 kDa laccase was confirmed as a major oxidase activity in extracts of lignifying compression xylem but it was barely detectable in the non-compression extracts where an 85 kDa oxidase was the predominant activity. The differential expression of oxidases in compression and non-compression xylem is discussed.
McDougall
G J
GJ
Unit of Plant Biochemistry, Biochemistry and Cell Biology Division, Scottish Crop Research Institute, Invergowrie, Dundee DD2 5DA, Scotland, UK. gmdou@scri.sari.ac.uk
D000595:Amino Acid Sequence; D004591:Electrophoresis, Polyacrylamide Gel; D042845:Laccase; D008969:Molecular Sequence Data; D010088:Oxidoreductases / Q000378:metabolism*; D010940:Plant Proteins / Q000737:chemistry / Q000378:metabolism*; D017386:Sequence Homology, Amino Acid; D014197:Trees / Q000201:enzymology / Q000254:growth & development* / Q000378:metabolism; D014934:Wood
D010940:Plant Proteins; D010088:Oxidoreductases; D042845:Laccase