A fluorescent hormone biosensor reveals the dynamics of jasmonate signalling in plants

Activated forms of jasmonic acid (JA) are central signals coordinating plant responses to stresses, yet tools to analyse their spatial and temporal distribution are lacking. Here we describe a JA perception biosensor termed Jas9-VENUS that allows the quantification of dynamic changes in JA distribution in response to stress with high spatiotemporal sensitivity. We show that Jas9-VENUS abundance is dependent on bioactive JA isoforms, the COI1 co-receptor, a functional Jas motif and proteasome activity. We demonstrate the utility of Jas9-VENUS to analyse responses to JA in planta at a cellular scale, both quantitatively and dynamically. This included using Jas9-VENUS to determine the cotyledon-to-root JA signal velocities on wounding, revealing two distinct phases of JA activity in the root. Our results demonstrate the value of developing quantitative sensors such as Jas9-VENUS to provide high-resolution spatiotemporal data about hormone distribution in response to plant abiotic and biotic stresses

Arabidopsis R-SNARE Proteins VAMP721 and VAMP722 Are Required for Cell Plate Formation

Background: Cell plate formation during plant cytokinesis is facilitated by SNARE complex-mediated vesicle fusion at the cell-division plane. However, our knowledge regarding R-SNARE components of membrane fusion machinery for cell plate formation remains quite limited. Methodology/Principal Findings: We report the in vivo function of Arabidopsis VAMP721 and VAMP722, two closely sequence-related R-SNAREs, in cell plate formation. Double homozygous vamp721vamp722 mutant seedlings showed lethal dwarf phenotypes and were characterized by rudimentary roots, cotyledons and hypocotyls. Furthermore, cell wall stubs and incomplete cytokinesis were frequently observed in vamp721vamp722 seedlings. Confocal images revealed that green fluorescent protein-tagged VAMP721 and VAMP722 were preferentially localized to the expanding cell plates in dividing cells. Drug treatments and co-localization analyses demonstrated that punctuate organelles labeled with VAMP721 and VAMP722 represented early endosomes overlapped with VHA-a1-labeled TGN, which were distinct from Golgi stacks and prevacuolar compartments. In addition, protein traffic to the plasma membrane, but not to the vacuole, was severely disrupted in vamp721vamp722 seedlings by subcellular localization of marker proteins. Conclusion/Significance: These observations suggest that VAMP721 and VAMP722 are involved in secretory trafficking to the plasma membrane via TGN/early endosomal compartment, which contributes substantially to cell plate formatio

Magnetoresistance Of Fe-ta-o Films Prepared By Rf Plasma Jet Method

The structure, magnetic and electric properties of Fe-Ta-O films prepared by the RF plasma jet technique were investigated. With increasing content of O the conductance changes from metallic to tunnelling one. In some films with the Fe/Ta ratio close to 0.25 the superparamagnetic properties and spin-dependent tunnelling magnetoresistance (with Ap/p up to 1.5% at 77.3 K) were observed. The behavior can be explained by the nanogranular structure consisting of ferromagnetic metallic grains embedded in an insulating amorphous matrix. © 2001 Elsevier Science B.V. All rights reserved.226-230PART I669670Mitani, S., Fujimori, H., Ohnuma, S., (1997) J. Magn. Magn. Mater., 165, p. 141Hayakawa, Y., Hasegawa, N., Makino, A., Mitani, S., Fujimori, H., (1996) J. Magn. Magn. Mater., 154, p. 175Soyka, V., Kraus, L., Frait, Z., Šícha, M., Jastrabik, L., (2000) Acta Phys. Polon. A, 97, p. 515Bárdoš, L., Vu, N.Q., (1989) Czech J. Phys. B, 39, p. 73