STRESSES MAKE WOOD YOUNGER? A CDNA MICROARRAY ANALYSIS OF JUVENILE AND MATURE WOOD DEVELOPMENT IN LOBLOLLY PINE

Forest Biotechnology Group, North Carolina State University, 6113 Jordan Hall, Raleigh, NC 27695-8008, USA

The presence and importance of juvenile and mature wood formation are well documented. Characteristics such as specific gravity, tracheid length, microfibril angle lignin and cellulose content differ between juvenile and mature wood. Results of differential gene expression studies by screening subtracted libraries showed that many genes are differentially expressed between juvenile and mature wood. The functions of these differentially expressed genes correspond well with the characteristics of juvenile and mature wood stated above. However, we also found that genes involved in stress responses are often among those that are highly differentially expressed. The distribution of juvenile wood within individual trees suggests that the presence of juvenile wood may be a response of the xylem cells to adapt to a stressful environment. A cDNA microarray approach was used to study the relationship between juvenile/mature wood formation and stresses. We profiled gene expression patterns of 3107 loblolly pine ESTs in developing xylem at juvenile and mature stages from three individuals, and compared them to expression patterns of two-year-old seedlings that had been subjected to heat, water and bending stresses. Correlation and multidimensional scaling analyses indicate two major clusters with juvenile wood formation and bending stress in one and heat and water stresses in the other. Further analyses using clustering and principal component analysis are currently being evaluated.