Pollen tube cell walls of wild and domesticated tomatoes contain arabinosylated and fucosylated xyloglucan.

BACKGROUND AND AIMS: In flowering plants, fertilization relies on the delivery of the sperm cells carried by the pollen tube to the ovule. During the tip growth of the pollen tube, proper assembly of the cell wall polymers is required to maintain the mechanical properties of the cell wall. Xyloglucan (XyG) is a cell wall polymer known for maintaining the wall integrity and thus allowing cell expansion. In most angiosperms, the XyG of somatic cells is fucosylated, except in the Asterid clade (including the Solanaceae), where the fucosyl residues are replaced by arabinose, presumably due to an adaptive and/or selective diversification. However, it has been shown recently that XyG of Nicotiana alata pollen tubes is mostly fucosylated. The objective of the present work was to determine whether such structural differences between somatic and gametophytic cells are a common feature of Nicotiana and Solanum (more precisely tomato) genera. METHODS: XyGs of pollen tubes of domesticated (Solanum lycopersicum var. cerasiforme and var. Saint-Pierre) and wild (S. pimpinellifolium and S. peruvianum) tomatoes and tobacco (Nicotiana tabacum) were analysed by immunolabelling, oligosaccharide mass profiling and GC-MS analyses. KEY RESULTS: Pollen tubes from all the species were labelled with the mAb CCRC-M1, a monoclonal antibody that recognizes epitopes associated with fucosylated XyG motifs. Analyses of the cell wall did not highlight major structural differences between previously studied N. alata and N. tabacum XyG. In contrast, XyG of tomato pollen tubes contained fucosylated and arabinosylated motifs. The highest levels of fucosylated XyG were found in pollen tubes from the wild species. CONCLUSIONS: The results clearly indicate that the male gametophyte (pollen tube) and the sporophyte have structurally different XyG. This suggests that fucosylated XyG may have an important role in the tip growth of pollen tubes, and that they must have a specific set of functional XyG fucosyltransferases, which are yet to be characterized.

Regulation of acetylation of plant cell wall components is complex and responds to external stimuli.

Previously, we reported that the allelic de-etiolated by zinc (dez) and trichome birefringence (tbr) mutants exhibit photomorphogenic development in the dark, which is enhanced by high Zn. TRICHOME BIREFRINGENCE-LIKE proteins had been implicated in transferring acetyl groups to various hemicelluloses. Pectin O-acetylation levels were lower in dark-grown dez seedlings than in the wild type. We observed Zn-enhanced photomorphogenesis in the dark also in the reduced wall acetylation 2 (rwa2-3) mutant, which exhibits lowered O-acetylation levels of cell wall macromolecules including pectins and xyloglucans, supporting a role for cell wall macromolecule O-acetylation in the photomorphogenic phenotypes of rwa2-3 and dez. Application of very short oligogalacturonides (vsOGs) restored skotomorphogenesis in dark-grown dez and rwa2-3. Here we demonstrate that in dez, O-acetylation of non-pectin cell wall components, notably of xyloglucan, is enhanced. Our results highlight the complexity of cell wall homeostasis and indicate against an influence of xyloglucan O-acetylation on light-dependent seedling development.