IRX14 and IRX14-LIKE （IRX14L） are two closely related glycosyl transferases in the glycosyl transferase 43 （GT43） family of Arabidopsis. A T-DNA insertion mutant for IRX14 results in comparatively minor changes, s...IRX14 and IRX14-LIKE （IRX14L） are two closely related glycosyl transferases in the glycosyl transferase 43 （GT43） family of Arabidopsis. A T-DNA insertion mutant for IRX14 results in comparatively minor changes, such as irregular xylem, while a mutation for IRX14L results in no changes. However, an irx14 and irx14L double mutant severely affects growth and development, with the dwarf plants failing to produce an inflorescence stem. Plants that are homozygous for IRX14 but heterozygous for IRX14L （irx14 irx14L（±）） exhibit an intermediate phenotype, including noticeably smaller leaves, stems, and underdeveloped siliques. Additionally, the T-DNA insertion mutant for IRX14 was found to result in a drought-tolerant phenotype. Carbohydrate analysis of total cell wall extracts revealed a reduction in xylose for the irx14 and irx14 irx14L（±） mutants, consistent with a defect in glucuronoxylan biosynthesis. Immunolocalization of xylan with the LM10 antibody revealed a loss of xylan in irx14 mutants and a further reduction in the irx14 irx14L（±） mutants. IRX14L likely functions redundantly with IRX14 in glucuronoxylan biosynthesis, with IRX14 having a more important role in the process.展开更多
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 cellul...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 （PtdCesAS） 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 pro- duced 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.展开更多
文摘IRX14 and IRX14-LIKE （IRX14L） are two closely related glycosyl transferases in the glycosyl transferase 43 （GT43） family of Arabidopsis. A T-DNA insertion mutant for IRX14 results in comparatively minor changes, such as irregular xylem, while a mutation for IRX14L results in no changes. However, an irx14 and irx14L double mutant severely affects growth and development, with the dwarf plants failing to produce an inflorescence stem. Plants that are homozygous for IRX14 but heterozygous for IRX14L （irx14 irx14L（±）） exhibit an intermediate phenotype, including noticeably smaller leaves, stems, and underdeveloped siliques. Additionally, the T-DNA insertion mutant for IRX14 was found to result in a drought-tolerant phenotype. Carbohydrate analysis of total cell wall extracts revealed a reduction in xylose for the irx14 and irx14 irx14L（±） mutants, consistent with a defect in glucuronoxylan biosynthesis. Immunolocalization of xylan with the LM10 antibody revealed a loss of xylan in irx14 mutants and a further reduction in the irx14 irx14L（±） mutants. IRX14L likely functions redundantly with IRX14 in glucuronoxylan biosynthesis, with IRX14 having a more important role in the process.
文摘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 （PtdCesAS） 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 pro- duced 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.
