Analysis of protein expression along the normal to tension wood gradient in Eucalyptus gunnii

This paper examines the contribution of various xylem proteins to wood formation in Eucalyptus gunnii. Proteins were extracted from differentiating xylem harvested from a crooked tree, separated by high-resolution two-dimensional polyacrylamide gel electrophoresis, visualised by silver nitrate staining and analysed with a computer-assisted system for single protein spot quantification. Growth strain measurements allowed xylem samples to be classified quantitatively from tension wood to normal wood. Regression of lignin content on growth strain showed that a decrease in lignin content corresponded to decreasing growth strain values, i.e., presence of tension wood. Out of the 140 studied protein spots, 12 were significantly associated with growth strain: 7 being less abundant in tension wood and 5 being more abundant in tension wood. A clustered-correlation analysis was performed to study protein expression simultaneously along the gradient of gravistimulated stressed xylem tissue. Proteins were found to form "expression clusters".