A large body of evidence supports the existence, in membrane from animal and yeast cells, of functional microdomains playing important roles in protein sorting, signal transduction, or infection by pathogens (1). We demonstrated the presence, in plants, of detergent resistant fractions isolated from plasma membrane, with a lipidic composition similar to animal microdomains (2). Electrophoresis experiments indicated that these fractions were able to recruit a specific set of plasma membrane proteins and exclude others. We used mass spectrometry to give an extensive description of a tobacco plasma membrane microdomains. This led to the identification of 145 proteins whose functional and physico-chemical characteristics were analysed in silico (3). This analysis indicated that if a primary function of the plasma membrane, such as transport, seems under-represented in microdomains, others, such as signalling and response to biotic and abiotic stress, undergo a significant increase of their relative importance. This suggests that these domains are likely to constitute, as in animal cells, signalling platforms involved in particular physiological processes. These results and others recently published (4) lead us to investigate more precisely the putative role played by such microdomains in the early interactions between plants and microorganisms, with a particular attention to reactive oxygen species metabolism. (1) Rajendran & Simons (2005) Journal of Cell Science 118, 1099-1102 (2) Mongrand et al (2004) Journal of Biological Chemistry 279 (35), 36277-36286 (3) Morel et al (2006) Molecular and Cellular Proteomics 5 (8), 1396-1411 (4) Bhat & Panstruga (2005) Planta 223 (1), 5-19