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Homogalacturonan synthesis in Arabidopsis thaliana requires a Golgi‐localized protein with a putative methyltransferase domain
Author(s) -
Mouille Grégory,
Ralet MarieChristine,
Cavelier Céline,
Eland Cathlene,
Effroy Delphine,
Hématy Kian,
McCartney Lesley,
Truong Hoai Nam,
Gaudon Virginie,
Thibault JeanFrançois,
Marchant Alan,
Höfte Herman
Publication year - 2007
Publication title -
the plant journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.058
H-Index - 269
eISSN - 1365-313X
pISSN - 0960-7412
DOI - 10.1111/j.1365-313x.2007.03086.x
Subject(s) - arabidopsis , golgi apparatus , mutant , biochemistry , arabidopsis thaliana , cell wall , biology , methylation , methyltransferase , chemistry , microbiology and biotechnology , gene , cell
Summary Pectins are a family of complex cell‐wall polysaccharides, the biosynthesis of which remains poorly understood. We identified dwarf mutants with reduced cell adhesion at a novel locus, QUASIMODO2 (QUA2). qua2‐1 showed a 50% reduction in homogalacturonan (HG) content compared with the wild type, without affecting other cell‐wall polysaccharides. The remaining HG in qua2‐1 showed an unaltered degree of methylesterification. Positional cloning and GFP fusions showed that QUA2, consistent with a role in HG synthesis, encodes a Golgi‐localized protein. In contrast to QUA1, another Golgi‐localized protein required for HG‐synthesis, QUA2 does not show sequence similarity to glycosyltransferases, but instead contains a putative methyltransferase (MT) domain. The Arabidopsis genome encodes 29 QUA2‐related proteins. Interestingly, the transcript profiles of QUA1 and QUA2 are correlated and other pairs of QUA1 and QUA2 homologues with correlated transcript profiles can be identified. Together, the results lead to the hypothesis that QUA2 is a pectin MT, and that polymerization and methylation of homogalacturonan are interdependent reactions.