摘要
Xylan is the major plant hemicellulosic poly- saccharide in the secondary cell wall. The transcription factor KNOTTED-LIKE HOMEOBOX OF ARABIDOPSIS THALIANA 7 （KNAT7） regulates secondary cell wall biosynthesis, but its exact role in regulating xylan biosynthesis remains unclear. Using transactivation analyses, we demonstrate that KNAT7 activates the promoters of the xylan biosynthetic genes, IRREGULAR XYLEM 9 （IRX9）, IRX10, IRREGULAR XYLEM 14-LIKE （IRX14L）, and FRAGILE FIBER 8 （FRAS）. The knat7 T-DNA insertion mutants have thinner vessel element walls and xylary fibers, and thicker interfascicular fiber walls in inflorescence stems, relative to wild-type （WT）. KNAT7 over- expression plants exhibited opposite effects. Glycosyl linkage and sugar composition analyses revealed lower xylan levels in knat7 inflorescence stems, relative to WT; a finding supported by labeling of inflorescence walls with xylan-specific antibodies. The knat7 loss-of-function mutants had lower transcript levels of the xylan biosynthetic genes IRX9, IRX10, and FRAS, whereas KNAT7 overexpression plants had higher mRNA levels for IRX9, IRX10, IRX14L, and FRA8. Electrophoretic mobility shift assays indicated that KNAT7 binds to the IRX9 promoter. These results support the hypothesis that KNAT7 positively regulates xylan biosynthesis.
Xylan is the major plant hemicellulosic poly- saccharide in the secondary cell wall. The transcription factor KNOTTED-LIKE HOMEOBOX OF ARABIDOPSIS THALIANA 7 （KNAT7） regulates secondary cell wall biosynthesis, but its exact role in regulating xylan biosynthesis remains unclear. Using transactivation analyses, we demonstrate that KNAT7 activates the promoters of the xylan biosynthetic genes, IRREGULAR XYLEM 9 （IRX9）, IRX10, IRREGULAR XYLEM 14-LIKE （IRX14L）, and FRAGILE FIBER 8 （FRAS）. The knat7 T-DNA insertion mutants have thinner vessel element walls and xylary fibers, and thicker interfascicular fiber walls in inflorescence stems, relative to wild-type （WT）. KNAT7 over- expression plants exhibited opposite effects. Glycosyl linkage and sugar composition analyses revealed lower xylan levels in knat7 inflorescence stems, relative to WT; a finding supported by labeling of inflorescence walls with xylan-specific antibodies. The knat7 loss-of-function mutants had lower transcript levels of the xylan biosynthetic genes IRX9, IRX10, and FRAS, whereas KNAT7 overexpression plants had higher mRNA levels for IRX9, IRX10, IRX14L, and FRA8. Electrophoretic mobility shift assays indicated that KNAT7 binds to the IRX9 promoter. These results support the hypothesis that KNAT7 positively regulates xylan biosynthesis.
基金
the National Key Research and Development Program of China(2016YFD0600105)
the National Natural Science Foundation of China(31670670,31670601)
the open Foundation(491170 K201703)of Provincial Key Laboratory of Agrobiology(Jiangsu Academy of Agricultural Sciences)
the Guangdong Province Science and Technology Projects(2015A050502045)
support of a grant from the Australia Research Council(ARC)to the ARC Centre of Excellence in Plant Cell Walls(CE110001007)
