TheTUMOROUS SHOOT DEVELOPMENT2gene of Arabidopsis encoding a putative methyltransferase is required for cell adhesion and co‐ordinated plant development

Abstract

SummaryMutations in the TUMOROUS SHOOT DEVELOPMENT2 (TSD2) gene reduce cell adhesion, and in strongly affected individuals cause non-coordinated shoot development that leads to disorganized tumor-like growth in vitro. tsd2 mutants showed increased activity of axial meristems, reduced root growth and enhanced deetiolation. The expression domains of the shoot meristem marker genes KNAT1 and KNAT2 were enlarged in the mutant background. Soil-grown tsd2 mutants were dwarfed, but overall showed morphology similar to that of the wild-type (WT). The TSD2 gene was identified by map-based cloning. It encodes a novel 684 amino acid polypeptide containing a single membrane-spanning domain in the N-terminal part and S-adenosyl-L-methionine binding and methyltransferase domains in the C-terminal part. Expression of a TSD2:GUS reporter gene was detected mainly in meristems and young tissues. A green fluorescent protein-tagged TSD2 protein localized to the Golgi apparatus. The cell-adhesion defects indicated altered pectin properties, and we hypothesize that TSD2 acts as a pectin methyltransferase. However, analyses of the cell-wall composition revealed no significant differences of the monosaccharide composition, the uronic acid content and the overall degree of pectin methylesterification between tsd2 and WT. The findings support a function of TSD2 as a methyltransferase, with an essential role in cell adhesion and coordinated plant development.

FLYING SAUCER1 Is a Transmembrane RING E3 Ubiquitin Ligase That Regulates the Degree of Pectin Methylesterification inArabidopsisSeed Mucilage

“…Although PMTs are predicted to have a single membranespanning domain (Krupková et al, 2007), this may not be sufficient for Golgi localization as the mechanisms for the retention of plant proteins in the Golgi are not well understood (SaintJore-Dupas et al, 2004). None of the 67 putative PMTs in the Arabidopsis genome have a confirmed biochemical activity (Harholt et al, 2010), and only a few, such as QUA2 (Mouille et al, 2007), QUA3 (Miao et al, 2011), and CGR3 (Held et al, 2011), are known to impact pectin biosynthesis.…”

Plant Callus: Mechanisms of Induction and Repression

“…TSD2, also known as QUASIMODO2 (QUA2) and OVERSENSITIVE TO SUGAR1 (OSU1), encodes a putative Golgi-localized methyltransferase (Mouille et al, 2007;Ralet et al, 2008;Gao et al, 2008). How TSD2/QUA2/OSU1 affects cell wall biosynthesis is not known, but tsd2/qua2/osu1 mutants show 50% reduction in the level of homogalacturonan, another major component of pectin, leading to severe defects in cell adhesion (Krupková et al, 2007;Mouille et al, 2007;Ralet et al, 2008). The overproliferation phenotypes of these cell wall mutants presumably are an indirect consequence of disrupted intercellular communication.…”

The ArabidopsisTUMOR PRONE5Gene Encodes an Acetylornithine Aminotransferase Required for Arginine Biosynthesis and Root Meristem Maintenance in Blue Light

“…The mapping was done with approximately 2,300 homozygous mutant plants of the F2 generation, as described by Krupková et al (2007). No more recombinants were found at a mapping interval of 88 kb.…”

“…The plant material was treated following the GUS staining protocol described by Krupková et al (2007). The tissue was cleared and mounted according to Malamy and Benfey (1997).…”