Members of glycosyltransferase protein families GT8, GT43 and GT47 are implicated in the biosynthesis of xylan in the secondary cell walls of @entity958 . The @entity958 mutant @entity70310 has a 60% reduction in xylan. However, over-expression of an ortholog of @entity958 @entity70310 , poplar PoGT8D, in @entity958 @entity70310 mutant could not restore xylan synthesis. The functions of tree GT8D genes remain unclear. We identified two GT8 gene homologs, PtrGT8D1 and PtrGT8D2, in @entity26340 . They are the only two GT8D members and are abundantly and specifically expressed in the differentiating xylem of @entity26340 . PtrGT8D1 transcript abundance was >7 times that of PtrGT8D2. To elucidate the genetic function of GT8D in @entity26340 , the expression of PtrGT8D1 and PtrGT8D2 was simultaneously knocked down through RNAi. Four transgenic lines had 85-94% reduction in transcripts of PtrGT8D1 and PtrGT8D2, resulting in 29-36% reduction in stem wood xylan content. Xylan reduction had essentially no effect on cellulose quantity but caused an 11-25% increase in lignin. These transgenics exhibit a brittle wood phenotype, accompanied by increased vessel diameter and thinner fiber cell walls in stem xylem. Stem modulus of elasticity and modulus of rupture were reduced by 17-29% and 16-23%, respectively, and were positively correlated with xylan content but negatively correlated with lignin quantity. These results suggest that PtrGT8Ds play key roles in xylan biosynthesis in wood. Xylan may be a more important factor than lignin affecting the stiffness and @entity174 strength of wood.

Down-regulation of glycosyltransferase 8D genes in XXXX caused reduced mechanical strength and xylan content in wood.

@entity958 :: ('3702', 'Species') :: ['Arabidopsis'] @entity26340 :: ('3694', 'Species') :: ['Populus trichocarpa', 'P. trichocarpa'] @entity70310 :: ('835558(Tax:3702)', 'Gene') :: ['IRX8', 'irx8'] @entity174 :: ('MESH:D050723', 'Disease') :: ['fracture']
@entity26340 :: (3694,Species) :: ['Populus trichocarpa']
