Investigating the molecular underpinnings underlying morphology and changes in carbon partitioning during tension wood formation in Eucalyptus.
Tension wood has distinct physical and chemical properties, including altered fibre properties, cell wall composition and ultrastructure. It serves as a good system for investigating the genetic regulation of secondary cell wall biosynthesis and wood formation. The reference genome sequence for Eucalyptus grandis allows investigation of the global transcriptional reprogramming that accompanies tension wood formation in this global wood fibre crop. We report the first comprehensive analysis of physicochemical wood property changes in tension wood of Eucalyptus measured in a hybrid (E. grandis × Eucalyptus urophylla) clone, as well as genome-wide gene expression changes in xylem tissues 3 wk post-induction using RNA sequencing. We found that Eucalyptus tension wood in field-grown trees is characterized by an increase in cellulose, a reduction in lignin, xylose and mannose, and a marked increase in galactose. Gene expression profiling in tension wood-forming tissue showed corresponding down-regulation of monolignol biosynthetic genes, and differential expression of several carbohydrate active enzymes. We conclude that alterations of cell wall traits induced by tension wood formation in Eucalyptus are a consequence of a combination of down-regulation of lignin biosynthesis and hemicellulose remodelling, rather than the often proposed up-regulation of the cellulose biosynthetic pathway.
Department of Genetics, Forestry and Agricultural Biotechnology Institute (FABI), University of Pretoria, Private bag X20, Pretoria, 0028, South Africa.
Eshchar
E
Mizrachi
Department of Wood Science, University of British Columbia, 4030-2424 Main Mall, Vancouver, BC, V6T 1Z4, Canada.
Victoria J
VJ
Maloney
Department of Genetics, Forestry and Agricultural Biotechnology Institute (FABI), University of Pretoria, Private bag X20, Pretoria, 0028, South Africa.
Janine
J
Silberbauer
Bioinformatics and Computational Biology Unit, Department of Biochemistry, University of Pretoria, Private Bag X20, Pretoria, 0028, South Africa.
Charles A
CA
Hefer
Department of Plant Science, Forestry and Agricultural Biotechnology Institute (FABI), University of Pretoria, Pretoria, 0002, South Africa.
Dave K
DK
Berger
Department of Wood Science, University of British Columbia, 4030-2424 Main Mall, Vancouver, BC, V6T 1Z4, Canada.
Shawn D
SD
Mansfield
Department of Genetics, Forestry and Agricultural Biotechnology Institute (FABI), University of Pretoria, Private bag X20, Pretoria, 0028, South Africa.
Alexander A
AA
Myburg
D053898:Biosynthetic Pathways; D002241:Carbohydrates / Q000235:genetics; D002244:Carbon / Q000378:metabolism*; D002473:Cell Wall / Q000378:metabolism; D002482:Cellulose / Q000378:metabolism; D003433:Crosses, Genetic; D015536:Down-Regulation; D005052:Eucalyptus / Q000033:anatomy & histology* / Q000235:genetics / Q000254:growth & development* / Q000378:metabolism; D018506:Gene Expression Regulation, Plant; D017343:Genes, Plant; D008031:Lignin / Q000378:metabolism; D014934:Wood / Q000033:anatomy & histology* / Q000235:genetics / Q000254:growth & development* / Q000378:metabolism; D052584:Xylem / Q000378:metabolism
D002241:Carbohydrates; D002244:Carbon; D002482:Cellulose; D008031:Lignin
Eucalyptus; RNA-seq; cellulose; hemicellulose; lignin; tension wood; transcriptome; xylan