The Helicoidal Cell Wall as a Time Register*

Abstract

Summary Helicoidal cell walls are characterized by an oscillatory shift in the arrangement of cellulose microfibrils somewhat reminiscent of the rotating movement of the hands of a clock. The periodic movement can be sustained or perturbed. Thus, the helicoidal cell wall presents a temporal reading. Sensitive to temporal signals, the cell wall keeps a record of cellular events and registers very small variations, storing data at a subcellular level. The present paper emphasizes some aspects of the helicoidal cell wall relevant to timekeeping, revealing its dynamics and flexibility and leading to the question of the mechanisms of its construction.

The rotation of cellulose synthase trajectories is microtubule dependent and influences the texture of epidermal cell walls inArabidopsis hypocotyls

“…To study the movement of the cellulose synthase GFP-CESA3, over the several hours required to deposit several wall layers (Takeda and Shibaoka, 1981;Vian and Roland, 1987), it was first necessary to calibrate the long-term behaviour of microtubules in cells grown in illuminated microscopy chambers (Chan et al, 2007). Microtubule rotation was studied by making z-stacks every 15 minutes for up to 24 hours in seedlings that expressed the tubulin marker TUA6-GFP.…”

“…In epidermal cells of mung bean hypocotyls, cellulose microfibrils have been reported to be laid down in strata of alternating 'criss-cross' alignment separated by fibrils intermediate between these orthogonal directions (Roland et al, 1977) -a pattern also reported in epidermal cells of oat (Sargent, 1978) and sunflower (Hodick and Kutschera, 1992). It has been reported to take about 3 hours for microfibrils to rotate through 180° (Vian and Roland, 1987). The progressive change in alignment between wall layers observed in chemically extracted and silver-stained mung bean stems by transmission electron microscopy has also been seen in freeze-fracture studies of the same tissue (Satiat-Jeunemaitre et al, 1992).…”

“…Here, we tested that hypothesis. We show that cellulose synthase particles also undergo full rotations over the several hours required for any rotary or oscillatory model for cell wall alignment (Takeda and Shibaoka, 1981;Vian and Roland, 1987). Over this time period, both polymer-promoting taxol and microtubuledestabilising oryzalin stopped the rotation of the cellulose synthase trajectories without stalling their rate of movement.…”

“…The main effect of these drugs is not, therefore, to stop wall formation but to affect its texture. According to self-assembly mechanisms for wall formation (Neville et al, 1976;Vian and Roland, 1987), each layer of microfibrils is aligned relative to its predecessor, without the need for a cytoplasmic template, as occurs in cholesteric liquid crystals. However, our studies demonstrate that the linear translocation of synthase particles is unable to be converted into rotary movement in the presence of microtubuledirected drugs, arguing against the idea that the drive for rotation originates from the wall.…”

Structure of epidermis wall, cuticle and cuticular microcracks in nectarine fruit

“…The presence of polysaccharide components at the junction of cuticle and wall is indicated by the fixation of silver granules of the reticulate fibrils in sections contrasted with the PATAg procedure (Thiery, 1967;Roland, 1978 (fig 17). Reis (1981Reis ( -1982 Vian and Roland, 1987 …”