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MUCILAGE-MODIFIED4 encodes a putative pectin biosynthetic enzyme developmentally regulated by APETALA2, TRANSPARENT TESTA GLABRA1, and GLABRA2 in the Arabidopsis seed coat.
- Source :
-
Plant physiology [Plant Physiol] 2004 Jan; Vol. 134 (1), pp. 296-306. Date of Electronic Publication: 2003 Dec 30. - Publication Year :
- 2004
-
Abstract
- The Arabidopsis seed coat epidermis undergoes a complex process of differentiation that includes the biosynthesis and secretion of large quantities of pectinaceous mucilage, cytoplasmic rearrangement, and secondary cell wall biosynthesis. Mutations in MUM4 (MUCILAGE-MODIFIED4) lead to a decrease in seed coat mucilage and incomplete cytoplasmic rearrangement. We show that MUM4 encodes a putative NDP-l-rhamnose synthase, an enzyme required for the synthesis of the pectin rhamnogalacturonan I, the major component of Arabidopsis mucilage. This result suggests that the synthesis of monosaccharide substrates is a limiting factor in the biosynthesis of pectinaceous seed coat mucilage. In addition, the reduced cytoplasmic rearrangement observed in the absence of a key enzyme in pectin biosynthesis in mum4 mutants establishes a causal link between mucilage production and cellular morphogenesis. The cellular phenotype seen in mum4 mutants is similar to that of several transcription factors (AP2 [APETALA2], TTG1 [TRANSPARENT TESTA GLABRA1], TTG2 MYB61, and GL2 [GLABRA2]). Expression studies suggest that MUM4 is developmentally regulated in the seed coat by AP2, TTG1, and GL2, whereas TTG2 and MYB61 appear to be regulating mucilage production through alternate pathway(s). Our results provide a framework for the regulation of mucilage production and secretory cell differentiation.
- Subjects :
- Adhesives metabolism
Amino Acid Sequence
Arabidopsis embryology
Arabidopsis Proteins genetics
Cell Differentiation
Cloning, Molecular
Gene Expression
Homeodomain Proteins genetics
Molecular Sequence Data
Mutation
Nuclear Proteins genetics
Phenotype
Seeds cytology
Seeds enzymology
Sequence Homology, Amino Acid
Arabidopsis enzymology
Arabidopsis genetics
Genes, Plant
Glycosyltransferases genetics
Glycosyltransferases metabolism
Pectins biosynthesis
Plant Proteins
Subjects
Details
- Language :
- English
- ISSN :
- 0032-0889
- Volume :
- 134
- Issue :
- 1
- Database :
- MEDLINE
- Journal :
- Plant physiology
- Publication Type :
- Academic Journal
- Accession number :
- 14701918
- Full Text :
- https://doi.org/10.1104/pp.103.035519