Localized stimulation of molecular signalling in single cells

Giesguth M. Localized stimulation of molecular signalling in single cells. Bielefeld; 2012

Redox-dependent translocation of the heat shock transcription factor AtHSFA8 from the cytosol to the nucleus in Arabidopsis thaliana

Giesguth M, Sahm A, Simon S, Dietz K-J. Redox-dependent translocation of the heat shock transcription factor AtHSFA8 from the cytosol to the nucleus in Arabidopsis thaliana. FEBS letters. 2015;589(6):718-725.The hypothesis is tested that some heat stress transcription factors (HSFs) are activated after formation of inter- or intramolecular disulfide bonds. Based on in silico analyses we identified conserved cysteinyl residues in AtHSFA8 that might function as redox sensors in plants. AtHSFA8 represents a redox-sensitive transcription factor since upon treatment of protoplasts with H2O2 YFP-labeled HSFA8 was translocated to the nucleus in a time-dependent manner. Site-directed mutagenesis of the conserved residues Cys24 and Cys269 blocked translocation of HSFA8 to the nucleus. The findings concur with a model where HSFA8 functions as redox sensing transcription factor within the stress-responsive transcriptional network

Thermomicrocapillaries as temperature biosensors in single cells

Herth S, Giesguth M, Wedel W, Reiss G, Dietz K-J. Thermomicrocapillaries as temperature biosensors in single cells. Applied Physics Letters. 2013;102(10): 103505.Temperature is an important physical parameter in biology and its deviation from optimum can cause damage in biosystems. Thermocouples based on the Seebeck effect can be structured on glass microcapillaries to obtain thermomicrocapillaries (TMCs) usable in a micromanipulation setup. The suitability of the setup was proven by monitoring the temperature increase upon illumination of leaves and single cells following insertion of the TMC. The increase was 1.5K in green tissue and 0.75K in white leaf sections due to lower absorption. In single cells of trichomes, the increase was 0.5K due to heat dissipation to the surrounding air. (C) 2013 American Institute of Physics

Magnetic tweezers for manipulation of magnetic particles in single cells

Ebrahimian H, Giesguth M, Dietz K-J, Reiss G, Herth S. Magnetic tweezers for manipulation of magnetic particles in single cells. Applied Physics Letters. 2014;104(6): 63701.Magnetic tweezers gain increasing interest for applications in biology. Here, a setup of magnetic tweezers is introduced using micropatterned conducting lines on transparent glass slides. Magnetic particles of 1 mu m diameter were injected in barley cell vacuoles using a microinject system under microscopic control. Time dependent tracking of the particles after application of a magnetic field was used to determine the viscosity of vacuolar sap in vivo relative to water and isolated vacuolar fluid. The viscosity of vacuolar sap in cells was about 2-fold higher than that of extracted vacuolar fluid and 5 times higher than that of water. (C) 2014 AIP Publishing LLC

PERPETUAL FLOWERING2 coordinates the vernalization response and perennial flowering in Arabis alpina

The floral repressor APETALA2 (AP2) in Arabidopsis regulates flowering through the age pathway. The AP2 ortholog in the alpine perennial Arabis alpina, PERPETUAL FLOWERING 2 (PEP2), was previously reported to control flowering through the vernalization pathway via enhancing the expression of another floral repressor PERPETUAL FLOWERING 1 (PEP1), the ortholog of Arabidopsis FLOWERING LOCUS C (FLC). However, PEP2 also regulates flowering independently of PEP1. To characterize the function of PEP2, we analyzed the transcriptomes of pep2 and pep1 mutants. The majority of differentially expressed genes were detected between pep2 and the wild type or between pep2 and pep1, highlighting the importance of the PEP2 role that is independent of PEP1. Here, we demonstrate that PEP2 activity prevents the up-regulation of the A. alpina floral meristem identity genes FRUITFUL (AaFUL), LEAFY (AaLFY), and APETALA1 (AaAP1), ensuring floral commitment during vernalization. Young pep2 seedlings respond to vernalization, suggesting that PEP2 regulates the age-dependent response to vernalization independently of PEP1. The major role of PEP2 through the PEP1-dependent pathway takes place after vernalization, when it facilitates PEP1 activation both in the main shoot apex and in axillary branches. These multiple roles of PEP2 in the vernalization response contribute to the A. alpina life cycle