Abstract
The laterally heterogeneous plant plasma membrane (PM) is organized into finely controlled specialized areas that include membrane-ordered domains. Recently, the spatial distribution of such domains within the PM has been identified as playing a key role in cell responses to environmental challenges. To examine membrane order at a local level, BY-2 tobacco suspension cell PMs were labelled with an environment-sensitive probe (di-4-ANEPPDHQ). Four experimental models were compared to identify mechanisms and cell components involved in short-term (1 h) maintenance of the ordered domain organization in steady-state cell PMs: modulation of the cytoskeleton or the cell wall integrity of tobacco BY-2 cells; and formation of giant vesicles using either a lipid mixture of tobacco BY-2 cell PMs or the original lipid and protein combinations of the tobacco BY-2 cell PM. Whilst inhibiting phosphorylation or disrupting either the cytoskeleton or the cell wall had no observable effects, we found that lipids and proteins significantly modified both the abundance and spatial distribution of ordered domains. This indicates the involvement of intrinsic membrane components in the local physical state of the plant PM. Our findings support a major role for the 'lipid raft' model, defined as the sterol-dependent ordered assemblies of specific lipids and proteins in plant PM organization.
Highlights
Plant cells are delimited by a plasma membrane (PM) that protects them against the external environment, and that regulates what enters the cell.The PM defines the boundary between the intracellular and extracellular space and plays a major role in transducing various signals into the appropriate adaptive responses
Our results suggest that PM components appear to act together to regulate plant PM heterogeneity, whilst neither the cytoskeleton nor the cell wall seem to play a significant role in the short-term control of ordered domain distribution within steady-state cell PMs
We previously described the heterogeneity of tobacco PM lateral organization with respect to local membrane order by Cytoskeleton remodelling does not modify the organization of PM-ordered domains
Summary
Plant cells are delimited by a plasma membrane (PM) that protects them against the external environment, and that regulates what (and how much) enters the cell.The PM defines the boundary between the intracellular and extracellular space and plays a major role in transducing various signals into the appropriate adaptive responses. The similar ability of plant-specific sterols to form an Lo phase has been reported in PM-purified fractions (Roche et al, 2008) as well as in living tobacco cells (Gerbeau-Pissot et al, 2014), with diffing capabilities to stabilize the lipid bilayer depending on the phytosterol structure (Rujanavech et al, 1986; Schuler et al, 1990, 1991; Hartmann, 1998; Halling and Slotte, 2004) This capacity of phytosterols to modulate the size and proportion of the Lo phase in the model membrane has been associated with their ability to interact with plant sphingolipids (Grosjean et al, 2015)
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