title: Perturbation of wood cellulose synthesis causes pleiotropic effects in transgenic aspen.
abstract: Genetic manipulation of cellulose biosynthesis in trees may provide novel insights into the growth and development of trees. To explore this possibility, the overexpression of an aspen secondary wall-associated cellulose synthase (PtdCesA8) gene was attempted in transgenic aspen (Populus tremuloides L.) and unexpectedly resulted in silencing of the transgene as well as its endogenous counterparts. The main axis of the transgenic aspen plants quickly stopped growing, and weak branches adopted a weeping growth habit. Furthermore, transgenic plants initially developed smaller leaves and a less extensive root system. Secondary xylem (wood) of transgenic aspen plants contained as little as 10% cellulose normalized to dry weight compared to 41% cellulose typically found in normal aspen wood. This massive reduction in cellulose was accompanied by proportional increases in lignin (35%) and non-cellulosic polysaccharides (55%) compared to the 22% lignin and 36% non-cellulosic polysaccharides in control plants. The transgenic stems produced typical collapsed or 'irregular' xylem vessels that had altered secondary wall morphology and contained greatly reduced amounts of crystalline cellulose. These results demonstrate the fundamental role of secondary wall cellulose within the secondary xylem in maintaining the strength and structural integrity required to establish the vertical growth habit in trees.
authors.affiliation: Biotechnology Research Center, School of Forest Resources and Environmental Sciences, Michigan Technological University, Houghton, MI 49931, USA. cpjoshi@mtu.edu
authors.forename: Chandrashekhar P
authors.initials: CP
authors.lastname: Joshi
authors.forename: Shivegowda
authors.initials: S
authors.lastname: Thammannagowda
authors.forename: Takeshi
authors.initials: T
authors.lastname: Fujino
authors.forename: Ji-Qing
authors.initials: JQ
authors.lastname: Gou
authors.forename: Utku
authors.initials: U
authors.lastname: Avci
authors.forename: Candace H
authors.initials: CH
authors.lastname: Haigler
authors.forename: Lisa M
authors.initials: LM
authors.lastname: McDonnell
authors.forename: Shawn D
authors.initials: SD
authors.lastname: Mansfield
authors.forename: Bemnet
authors.initials: B
authors.lastname: Mengesha
authors.forename: Nicholas C
authors.initials: NC
authors.lastname: Carpita
authors.forename: Darby
authors.initials: D
authors.lastname: Harris
authors.forename: Seth
authors.initials: S
authors.lastname: Debolt
authors.forename: Gary F
authors.initials: GF
authors.lastname: Peter
mesh_terms: D002482:Cellulose / Q000378:metabolism*; D005964:Glucosyltransferases / Q000235:genetics / Q000378:metabolism; D008031:Lignin / Q000378:metabolism; D030821:Plants, Genetically Modified / Q000235:genetics / Q000254:growth & development / Q000378:metabolism; D032107:Populus / Q000235:genetics / Q000254:growth & development* / Q000378:metabolism*
chemical_list: D002482:Cellulose; D008031:Lignin; D005964:Glucosyltransferases; C478648:cellulose synthase