Search

Summary Plants have a highly sophisticated endomembrane system that is targeted by plant viruses for cell-to-cell movement. The movement protein (MP) of Ourmia melon virus (OuMV) is targeted to plasmodesmata (PD) and forms tubules to facilitate cell-to-cell movement. Despite a number of functionally important regions for correct subcellular localization of OuMV MP has been identified, little is known about the pathways OuMV MP hijacks to reach PD. Here, we demonstrate that OuMV MP localizes to the trans-Golgi network (TGN), but not to the multivesicular body/prevacuolar compartment or Golgi, and carries two putative sorting motifs, a tyrosine (Y) and a dileucine (LL) motif, near its N-terminus. Introducing glycine substitutions in these motifs results in loss of OuMV infectivity in Nicotiana benthamiana and Arabidopsis ( Arabidopsis thaliana ). Live cell imaging of GFP-labeled sorting motif mutants shows that Y motif mutants fail to localize to the TGN, plasma membrane, and PD. Mutations in the LL motif do not impair plasma membrane targeting of MP, but affect its ability to associate with callose deposits at PD. Taken together, these data suggest that both Y and LL motifs are indispensable for targeting of OuMV MP to PD and for efficient systemic infection, but show differences in functionality. This study provides new insights into the role of sorting motifs in intracellular targeting of MPs and vesicle trafficking pathways that plant viruses hijack for cell-to-cell movement.

Label-free detection of the interaction between hexahistidine-tagged human kappa-opioid receptor membrane protein and anti-His antibody is demonstrated in liquid by an optical microelectromechanical system utilizing electromagnetically actuated microresonators Shift in resonance frequency due to accretion of mass on the sensitive surface of microresonators is monitored via an integrated optical readout A frequency resolution of 2 Hz is obtained Together with a sensitivity of 7 ppm/(ng/ml)) this leads to a minimum detectable antibody concentration of 57 ng/ml for a 50-kHz device The measurement principle is shown to impart immunity to environmental noise, facilitate operation in liquid media and bring about the prospect for further miniaturization of actuator and readout leading to a portable biochemical sensor (C) 2010 Elsevier B V All rights reserved.

Nickel cantilevers with integrated diffraction gratings are used as resonant mass sensors with a resolution of 500 femtograms. Their applicability to biosensing is demonstrated with human opioid receptors. The device is fabricated through a single-mask lithographic process. The microoptical readout provides a simple measurement platform with one external photodiode. Thanks to its ac operation principle, the device is immune to environmental noise and entails a high tolerance to fabrication defects. Obtained signal-to-noise ratio is comparable to that of a high-end Doppler vibrometer. The device with these aspects for systems integration and microarray technology is a candidate for low-cost portable sensors.