Expression of genes of cellulose and lignin synthesis in Eucalyptus urophylla and its relation to some economic traits

Abstract

Genes of cellulose and lignin synthesis are important for tree breeding because their activity greatly affects wood properties as well as general growth. The expression (transcript abundance) of genes of cellulose and lignin synthesis in tangential xylem scrapes at breast height sampled at the end of June (middle of active growing season) was related to wood properties in five fast-growing and six slow-growing families of Eucalyptus urophylla from a combined progeny test and seedling seed orchard grown for 10 years in northern Vietnam. Cellulose synthase A (CesA) genes encoding proteins active in the primary cell wall, EuCesA4 and EuCesA5, were more highly expressed than EuCesA1, EuCesA2 and EuCesA3, encoding genes active in the secondary cell wall. EuCesA4 expression was correlated with that of EuCesA5 (r = 0.49, P = 0.040) and EuCesA5 with EuCesA6 (r = 0.46, P = 0.040). EuCesA4 expression was significantly higher in the fast-growing group and was correlated with cellulose content (r = 0.51, P = 0.011). Over 2 kb of the EuCesA gene was sequenced in 24 trees extending from the 5′ untranslated region through six exons and six introns and revealed 83 polymorphisms and rapid decay of linkage disequilibrium over 500 bp. EuCesA4 activity in xylem is involved in the genetic control of cellulose content, and the gene may have potential for marker-aided selection.