Arabidopsis leaf plasma membrane proteome using a gel free method: Focus on receptor–like kinases

The hydrophobic proteins of plant plasma membrane still remain largely unknown. for example in thearabidopsis genome, receptor-like kinases (rlks) are plasma membrane proteins, functioning as the primaryreceptors in the signaling of stress conditions, hormones and the presence of pathogens form a diverse familyof over 610 genes. a limited number of these proteins have appeard in protein profiles. the detection of theseproteins and thus the determination of their dynamics and tissue specificity, is technically challenging due totheir low abundance and association to a lipid membrane. to identify new putative membrane proteinsespecially receptor systems, we used a gel free proteomic strategy based on mass spectrometry analyses of aplasma membrane fraction enriched in hydrophobic proteins. we produced from arabidopsis leaf a highlypurified plasma membrane fraction with the aqueous two-phase partitioning technique. by separating theproteins in the plasma membrane fraction with ion exchange and reverse phase chromatography and analyzingthe resulting fractions on a maldi-tof mass spectrometer, over 900 proteins were detected. the plasmamembrane proteome generated by this approach contains numerous plasma membrane integral proteins, onethirddisplaying at least four trans-membrane segments. an in silico analysis shows a correlation between theputative functions of the identified proteins and the expected roles for plasma membrane in transport,signaling, cellular traffic and metabolism. of these proteins, 304 were annotated as membrane proteins, 69were rlks, distributed among the different receptor families in proportions reflecting the distribution in thegenome. of the rlks that were identified, most are reported for the first time at the protein level and willconstitute interesting targets for further functional studies.