Towards the elucidation of maize plasma membrane aquaporin interactions
(2011)
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- Authors
- Supervisors
- Chaumont, François
- Abstract
- (en) Plant growth and development are dependent on a tight regulation of water uptake and movement across membranes and tissues. The role of aquaporins in regulating this water flow is currently believed to be determinant. Aquaporins are membrane channel proteins that facilitate the diffusion of water and small neutral solutes across membranes. In comparison to animals, plants express a much higher number of aquaporin genes. This large number of isoforms probably offers adaptative advantages for growth in different environmental conditions as a result of divergent substrate specificity, localisation, transcriptional and post-translational regulation. To better understand the function of maize plasma membrane aquaporins (PIPs, plasma membrane intrinsic proteins) in plants and suspension cells, specific antibodies raised against different ZmPIP isoforms were obtained and used to investigate PIP expression and localisation. A quantitative analysis at the protein level demonstrated a general good correlation with the data obtained at the mRNA level. In maize suspension cells, a general increase of aquaporin expression was observed during culture growth. In these cells, ZmPIP2;6 was expressed mainly in the plasma membrane but also in internal vesicles. The localisation of ZmPIP1;2 and ZmPIP2;6 in the root elongation zone of 7 day-old maize seedlings might be explained by a phloem unloading process. The polar localisation of ZmPIP2;6 and ZmPIP1;2 to the external periclinal side of epidermal root cells and the localisation pattern in the mature zone indicate a role in water uptake and transport. A conserved cysteine residue located in the extra-cytosolic loop A of PIPs was shown to be involved in the formation of a disulfide bridge between two monomers. A probable role of this disulfide bond in protein stability has to be investigated. By immunoprecipitation and affinity chromatography experiments, we showed that proteins belonging to the PIP2 subgroup can physically interact in maize suspension cells and Xenopus oocytes and these interactions occur probably within a heterotetramer consisting of two homodimers. The actual molecular interactors of plant aquaporins in the secretory pathway and plasma membrane are mostly unknown and our knowledge of the routing process is still elusive. In this work, two different approaches to identify interacting proteins by mass spectrometry were elaborated. Preliminary results led to the identification of several potential interacting partners.
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Citations
Cavez, D. (2011). Towards the elucidation of maize plasma membrane aquaporin interactions. https://hdl.handle.net/2078.5/75071