Plant & Animal Genome VI Conference

W43

AVERAGE EFFECT OF A MUTATION IN LIGNIN BIOSYNTHESIS IN LOBLOLLY PINE

Forest Biotechnology Group, Department of Forestry, North Carolina State University, Raleigh, NC 27695-8008

Cinnamyl alcohol dehydrogenase (CAD, E.C. 1.1.1.195) is a monolignol biosynthetic enzyme that catalyzes the final step of lignin subunit biosynthesis in higher plants. More recently, a mutant allele of the cad gene encoding for the CAD enzyme was discovered in loblolly pine. By reducing the expression of the cad gene, this mutant, described as cad-n1, can lead to decreased lignin content and major changes in lignin composition of wood. In this study, we found that the substitution of a wild type allele by cad-n1 was associated with a significant average effect on 2nd-year shoot elongation (3.6%) in a half-sib family of loblolly pine 7-1037. The effect associated with the cad mutant allele was still significant when systematic environmental errors were removed from the phenotypic data using spatial analysis. The average effect of cad-n1 appeared to increase with tree development and was larger on the secondary than primary growth of wood. For example, an increase of 14.1% in debarked volume index in year 4 was associated with cad-n1. Co-segregation analysis indicated that the locus itself might represent a gene that governs stem growth in pine. The significance of the mutated cad-n1 in paper industry and evolutionary studies is discussed.