Diffusion of water through cell membranes is facilitated by aquaporins (AQPs). Regulation of AQP activity provides plants with the means to modify rapidly and reversibly water membrane permeability1. Plasma membrane (PM) intrinsic proteins (PIPs) are a subfamily of AQPs located mainly in the PM of plant cells. In the PM some channels are restricted in microdomains whereas others move freely (Li et al, Plant Cell 2011 23: 3780–3797). Additionally, PIPs seem to be in close interaction with other cellular structures such as the actin filaments (Hosy et al, Molecular Plant 2015; 8: 339– 342) and we showed that PM-located PIPs interact with the endoplasmic reticulum (ER) resident VAP27s at ER–PM contact sites (EPCS) (Fox et al, New Phytologist 2020; 228: 973-988). Altogether, the evidence points to the existence of PM-organized PIP channels in interaction with proteins from other cellular structures. However, in-depth investigation integrating all the components (PIP microdomains-EPCS-cytoskeleton) is missing.
In this context, we proposed the PIPContactSite project, whose the main objective was to determine whether ZmPIP2s mediate PM interaction with other cellular structures (ER, cytoskeleton) and elucidate the physiological impact of those interactions under stress. Our central hypothesis is that ZmPIP2 interaction with EPCS and the cytoskeleton contributes to an efficient response to stimuli by its participation in the structural organization of the cell. If this is confirmed, it would mean that PIPs are not only playing a role as channels, but also as a scaffold for PM reorganization to initiate cellular response upon stress. The specific objectives of the project included:
1. Comprehensive characterization of the role of ZmPIP2s in the organization of ZmVAP-loaded EPCS.
2. Exploration of ZmPIP2 interactions and roles in the cytoskeleton organization.
3. Highlighting ZmPIP2;5 interactions in EPCS and cytoskeleton.
