title: Gene expression in Eucalyptus branch wood with marked variation in cellulose microfibril orientation and lacking G-layers.
abstract: In response to gravitational stresses, angiosperm trees form tension wood in the upper sides of branches and leaning stems in which cellulose content is higher, microfibrils are typically aligned closely with the fibre axis and the fibres often have a thick inner gelatinous cell wall layer (G-layer). Gene expression was studied in Eucalyptus nitens branches oriented at 45 degrees using microarrays containing 4900 xylem cDNAs, and wood fibre characteristics revealed by X-ray diffraction, chemical and histochemical methods. Xylem fibres in tension wood (upper branch) had a low microfibril angle, contained few fibres with G-layers and had higher cellulose and decreased Klason lignin compared with lower branch wood. Expression of two closely related fasciclin-like arabinogalactan proteins and a beta-tubulin was inversely correlated with microfibril angle in upper and lower xylem from branches. Structural and chemical modifications throughout the secondary cell walls of fibres sufficient to resist tension forces in branches can occur in the absence of G-layer enriched fibres and some important genes involved in responses to gravitational stress in eucalypt xylem are identified.
authors.affiliation: CSIRO Forest Biosciences, PO Box E4008, Kingston ACT 2604, Australia.
authors.forename: Deyou
authors.initials: D
authors.lastname: Qiu
authors.affiliation: CSIRO Plant Industry, PO Box 1600, Canberra ACT 2001, Australia.
authors.forename: Iain W
authors.initials: IW
authors.lastname: Wilson
authors.affiliation: CSIRO Forest Biosciences, PO Box E4008, Kingston ACT 2604, Australia.
authors.forename: Siming
authors.initials: S
authors.lastname: Gan
authors.affiliation: CSIRO Forest Biosciences, Private Bag 10, Clayton South VIC 3168, Australia.
authors.forename: Russell
authors.initials: R
authors.lastname: Washusen
authors.affiliation: CSIRO Forest Biosciences, PO Box E4008, Kingston ACT 2604, Australia.
authors.forename: Gavin F
authors.initials: GF
authors.lastname: Moran
authors.affiliation: CSIRO Forest Biosciences, PO Box E4008, Kingston ACT 2604, Australia.
authors.forename: Simon G
authors.initials: SG
authors.lastname: Southerton
mesh_terms: D015152:Blotting, Northern; D002473:Cell Wall / Q000235:genetics* / Q000648:ultrastructure; D002482:Cellulose / Q000032:analysis; D005052:Eucalyptus / Q000235:genetics* / Q000254:growth & development / Q000648:ultrastructure; D020869:Gene Expression Profiling; D008031:Lignin / Q000032:analysis; D020894:Microfibrils / Q000235:genetics* / Q000648:ultrastructure; D020411:Oligonucleotide Array Sequence Analysis; D010802:Phylogeny; D010940:Plant Proteins / Q000235:genetics* / Q000502:physiology; D018547:Plant Stems / Q000235:genetics* / Q000254:growth & development / Q000648:ultrastructure; D014934:Wood / Q000737:chemistry; D014961:X-Ray Diffraction; D052584:Xylem / Q000235:genetics / Q000254:growth & development / Q000648:ultrastructure
chemical_list: D010940:Plant Proteins; D002482:Cellulose; D008031:Lignin