Applications of Metabolic Profiling in the Study of Wood Formation

Abstract

In this work, a method of metabolic profiling of developing xylem tissue was developed and utilized in various applications. The first study examines the metabolic differences between four families of trees, involved in a tree breeding program, that exhibit different levels of α-cellulose content. Profiling results detect an increase in the concentration levels of glucose in the high α-cellulose samples. In the low α-cellulose samples, there was an accumulation of fructose and sucrose. The accumulation of sucrose in the low α-cellulose samples suggests an inhibition of P-Susy, which converts sucrose to UDP-glucose.

The second α-cellulose study utilizes clones that were planted on two different sites. One clone was classified as a high α-cellulose clone and the other as a low α-cellulose clone. By having the clones planted on two different sites, metabolic variations between the clones were observed on the same site and between sites, allowing a comparison of genetic and environmental differences associated with cellulose content. Based on the statistical analysis of the profiling data, the genetic differences associated with the high α-cellulose clone is an increase in the concentration levels of alanine, phosphoric acid, and free sugars, fructose, glucose, and mannose. The accumulation of fructose suggests that the greater amounts of cellulose produced releases more fructose in the cell that is not be recycled or slow to be recycled back into the cellulose biosynthesis.

Tree growth was also studied to examine the metabolic variation and transcript levels of genes associated with growth. Two families grown on a genetic site were chosen from a group of families based on their differences in average tree height. Statistical analysis of the profiling data identifies glutamine as a metabolite that has a positive correlation with tree height. Microarray results identify a NAM (no apical meristem)-like protein as being overly expressed in the fast growing family. NAM is a protein that regulates shoot apical meristem formation, which is responsible for vertical growth.

The last study, examines the metabolic effects of BWA infestation on the Fraser Fir species. In response to the feeding process of the BWA various changes occur in the tree metabolism, creating an increase in the concentration levels of shikimic acid, polyols, and some amino acids. The accumulations of polyols and amino acids suggest infestation causes the trees to enter a state of water stress.