The development of a plant feedstock more suitable for bioenergy production requires the understanding the genetic regulation of wood chemical properties. Our group identified a major gene that regulates carbon partitioning and growth on chromosome 13 (cpg13) of a poplar hybrid population, using genetical genomics approach. A major QTL that explains 56% of the variation in cellulose to lignin ratio, as well as 20-25% of the heritable variation of several biomass productivity traits was detected. The expression of cpg13 is highly correlated with lignin (r =0.41) and cellulose (r=-0.41), and moderately correlated with shoot biomass (r=-0.18) in the poplar hybrid mapping population. A transcriptome analysis shows that cpg13 is mostly expressed in tissues undergoing secondary cell wall formation. High expression correlation and sharing of motifs with other lignin biosynthesis genes provide further evidence of cpg13 interaction with this pathway. Putative homologues of cpg13 in Arabidopsis are annotated as proteins with unknown function; therefore, the functional characterization of cpg13 is essential. Currently, evidence of the functional role of cpg13 is being obtained by the analysis of poplar genetically modified that down-regulate (RNAi) and up-regulate cpg13 expression levels. Transcriptomics, wood chemical and biomass traits are going to be analyzed in plants grown under controlled environment. Furthermore, enzymatic assay with cpg13 protein will be performed to uncover its function.