Plant mitochondrial retrograde signaling: post-translational modifications enter the stage

Beside their central function in respiration plant mitochondria play important roles in diverse processes such as redox homeostasis, provision of precursor molecules for essential biosynthetic pathways, and programmed cell death. These different functions require the organelle to communicate with the rest of the cell by perceiving, transducing, and emitting signals. As the vast majority of mitochondrial proteins are encoded in the nuclear genome, changes in mitochondrial status must be fed back to the nucleus to coordinate gene expression accordingly, a process termed retrograde signaling. However, the nature of these signaling pathways in plants and their underlying signaling molecules - or indirect metabolite or redox signals are not completely resolved. We explore the potential of different post-translational modifications (PTMs) to contribute to mitochondrial retrograde signaling. Remarkably, the substrates used for modifying proteins in many major PTMs are either central metabolites or redox-active compounds, as for example ATP acetyl-CoA, NAD(+), and glutathione. This suggests that the metabolic status of organelles and of the cell in general could be indirectly gaged by the enzymes catalyzing the various PTMs. We examine the evidence supporting this hypothesis with regard to three major PTMs, namely phosphorylation, lysine acetylation, and glutathionylation and assess their potential to regulate not only organellar processes by modifying metabolic enzymes but also to influence nuclear gene expression

Radiative Corrections to the decay tau -> pi (K) nu_tau

We have calculated the O(alpha) radiative corrections to the tau decay tau -> pi (K) nu, taking into account both the point meson contribution and the structure dependent radiation. We find for the ratio Gamma(tau -> pi nu (gamma)) / Gamma(pi -> mu nu (gamma)) a radiative correction of + 1.2% and for Gamma(tau -> K nu (gamma)) / Gamma(K -> mu nu (gamma)) one of + 2.0%. We compare our results with an earlier estimation and with experimental data.Comment: 6 pages, Latex, Karlsruhe Univ. Preprint TTP 93-2

Radiative Corrections to the Decay τ→πντ\tau\to\pi\nu_\tau

We have calculated the radiative corrections to the decay $\tau\to \pi(K) \nu_\tau$, taking to account internal bremsstrahlung and structure dependent radiation in the radiative decay and point meson, hadronic structure dependent and short distance contributions in the virtual corrections. We display the spectra of the photon energy and of the pion-photon invariant mass in the decay $\tau\to\pi\nu_\tau\gamma$ and compare with the PHOTOS Monte-Carlo. Our result for the radiative correction to the ratio $\Gamma(\tau\to\pi\nu_\tau(\gamma))/ \Gamma(\pi\to\mu\nu_\mu(\gamma))$ is $\delta R_{\tau/\pi} = \left(0.16 \pm 0.14 \right) \%$ and for the ratio $\Gamma(\tau\to K\nu_\tau(\gamma))/ \Gamma(K\to\mu\nu_\mu(\gamma))$, we obtain $\delta R_{\tau/K } = \left(0.90 \pm 0.22 \right) \%$.Comment: 12 pages, Latex, using: epsfig, subfigure, rotating. 9 figures not included, complete Postscript file (including the figures) available via e-mail on request. Invited talk at the Third Workshop on Tau Lepton Physics (Montreux, September 94), presented by Markus Finkemeie

Reparametrization invariance reexamined

Reparameterization invariance, a symmetry of heavy quark effective theory, appears in different forms in the literature. The most commonly cited forms of the reparameterization transformation are shown to induce the same constraints on operators that do not vanish under the equation of motion to order 1/m2 , and to be related by a redefinition of the heavy quark field. We give a new, very straightforward proof that that the reparameterization invariance constraints apply to all orders in αs under matching to full QCD and renormalization-group running, at least up to and including O(1/m2).Physic