A sister of PIN1 gene in tomato (Solanum lycopersicum) defines leaf and flower organ initiation patterns by maintaining epidermal auxin flux

AbstractThe spatiotemporal localization of the plant hormone auxin acts as a positional cue during early leaf and flower organogenesis. One of the main contributors to auxin localization is the auxin efflux carrier PIN-FORMED1 (PIN1). Phylogenetic analysis has revealed that PIN1 genes are split into two sister clades; PIN1 and the relatively uncharacterized Sister-Of-PIN1 (SoPIN1). In this paper we identify entire-2 as a loss-of-function SlSoPIN1a (Solyc10g078370) mutant in Solanum lycopersicum. The entire-2 plants are unable to specify proper leaf initiation leading to a frequent switch from the wild type spiral phyllotactic pattern to distichous and decussate patterns. Leaves in entire-2 are large and less complex and the leaflets display spatial deformities in lamina expansion, vascular development, and margin specification. During sympodial growth in entire-2 the specification of organ position and identity is greatly affected resulting in variable branching patterns on the main sympodial and inflorescence axes. To understand how SlSoPIN1a functions in establishing proper auxin maxima we used the auxin signaling reporter DR5: Venus to visualize differences in auxin localization between entire-2 and wild type. DR5: Venus visualization shows a widening of auxin localization which spreads to subepidermal tissue layers during early leaf and flower organogenesis, showing that SoPIN1 functions to focus auxin signaling to the epidermal layer. The striking spatial deformities observed in entire-2 help provide a mechanistic framework for explaining the function of the SoPIN1 clade in S.lycopersicum

Measurement of the Fermi Constant by FAST

An initial measurement of the lifetime of the positive muon to a precision of 16 parts per million (ppm) has been performed with the FAST detector at the Paul Scherrer Institute. The result is tau_mu = 2.197083 (32) (15) microsec, where the first error is statistical and the second is systematic. The muon lifetime determines the Fermi constant, G_F = 1.166353 (9) x 10^-5 GeV^-2 (8 ppm).Comment: 15 pages, 6 figure

Pattern formation in leaves via small RNA mobility

Small RNAs, including microRNAs (miRNAs) and trans-acting short interfering RNAs (ta-siRNAs), have important regulatory roles in development. In plants, members of these classes of small RNAs act to pattern the adaxial–abaxial (dorsal–ventral) axis of leaves. The AUXIN-RESPONSE FACTOR (ARF) family members ARF3 and ARF4 are together necessary to establish abaxial (ventral) fate in leaves. ARF3 and ARF4 are targets of ta-siRNAs that are termed “tasiR-ARFs.” To begin to understand the possible role of tasiR-ARFs in leaf polarity, we have localized the biogenesis components of the tasiR-ARF pathway, including the microRNA miR390, the activity of the ARGONAUTE gene required for miR390 activity (AGO7), and the activity of tasiR-ARFs themselves. We provide evidence that the tasiR-ARF pathway in Arabidopsis acts non-cell autonomously to maintain the polarized accumulation of ARF3 in leaf primordia. Small RNAs (both miR390 and tasiR-ARFs) in this specialized RNAi pathway may contribute to its non-cell autonomous activity, as they accumulate outside their discrete regions of biogenesis. We propose that small RNAs can possibly function as mobile inductive signals to direct patterning events during developmen

Caloric curve in Au + Au collisions

Realistic caloric curves are obtained for $^{197}Au + ^{197}Au$ reaction with incident energy ranging from 35 to 130 MeV/nucleon in the dynamic statistical multifragmentation model. It is shown that for excitation energy 3 to 8 MeV/nucleon, the temperature remains constant in the range 5 to 6 MeV, which is close to experiment. The mechanism of energy deposition through the tripartition of colliding system envisaged in this model together with inter-fragment nuclear interaction are found to play important role. A possible signature of liquid-gas phase transition is seen in the specific heat distribution calculated from these caloric curves, and the critical temperature is found to be $\sim$ 6 to 6.5 MeV.Comment: Revtex, 10 pages, 4 postscipt figures, To appear in Phys. Rev. C (Rapid Communications

Regulation of Small RNA Accumulation in the Maize Shoot Apex

MicroRNAs (miRNAs) and trans-acting siRNAs (ta-siRNAs) are essential to the establishment of adaxial–abaxial (dorsoventral) leaf polarity. Tas3-derived ta-siRNAs define the adaxial side of the leaf by restricting the expression domain of miRNA miR166, which in turn demarcates the abaxial side of leaves by restricting the expression of adaxial determinants. To investigate the regulatory mechanisms that allow for the precise spatiotemporal accumulation of these polarizing small RNAs, we used laser-microdissection coupled to RT-PCR to determine the expression profiles of their precursor transcripts within the maize shoot apex. Our data reveal that the pattern of mature miR166 accumulation results, in part, from intricate transcriptional regulation of its precursor loci and that only a subset of mir166 family members contribute to the establishment of leaf polarity. We show that miR390, an upstream determinant in leaf polarity whose activity triggers tas3 ta-siRNA biogenesis, accumulates adaxially in leaves. The polar expression of miR390 is established and maintained independent of the ta-siRNA pathway. The comparison of small RNA localization data with the expression profiles of precursor transcripts suggests that miR166 and miR390 accumulation is also regulated at the level of biogenesis and/or stability. Furthermore, mir390 precursors accumulate exclusively within the epidermal layer of the incipient leaf, whereas mature miR390 accumulates in sub-epidermal layers as well. Regulation of miR390 biogenesis, stability, or even discrete trafficking of miR390 from the epidermis to underlying cell layers provide possible mechanisms that define the extent of miR390 accumulation within the incipient leaf, which patterns this small field of cells into adaxial and abaxial domains via the production of tas3-derived ta-siRNAs

Measurement of the Rate of Muon Capture in Hydrogen Gas and Determination of the Proton's Pseudoscalar Coupling gPg_P

The rate of nuclear muon capture by the proton has been measured using a new experimental technique based on a time projection chamber operating in ultra-clean, deuterium-depleted hydrogen gas at 1 MPa pressure. The capture rate was obtained from the difference between the measured $\mu^-$ disappearance rate in hydrogen and the world average for the $\mu^+$ decay rate. The target's low gas density of 1% compared to liquid hydrogen is key to avoiding uncertainties that arise from the formation of muonic molecules. The capture rate from the hyperfine singlet ground state of the $\mu p$ atom is measured to be $\Lambda_S=725.0 \pm 17.4 s^{-1}$, from which the induced pseudoscalar coupling of the nucleon, $g_P(q^2=-0.88 m_\mu^2)=7.3 \pm 1.1$, is extracted. This result is consistent with theoretical predictions for $g_P$ that are based on the approximate chiral symmetry of QCD.Comment: submitted to Phys.Rev.Let

Effect of Flow on Caloric Curve for Finite Nuclei

In a finite temperature Thomas-Fermi theory, we construct caloric curves for finite nuclei enclosed in a freeze-out volume few times the normal nuclear volume, with and without inclusion of flow. Without flow, the caloric curve indicates a smooth liquid-gas phase transition whereas with flow, the transition may be very sharp. We discuss these results in the context of two recent experiments, one for heavy symmetric system (Au + Au at 600A MeV) and the other for highly asymmetric system (Au + C at 1A GeV) where different behaviours in the caloric curves are seen.Comment: 11 pages revtex; 4 figs; version to appear in Phys. Rev. Let

Improved Measurement of the Positive Muon Lifetime and Determination of the Fermi Constant

The mean life of the positive muon has been measured to a precision of 11 ppm using a low-energy, pulsed muon beam stopped in a ferromagnetic target, which was surrounded by a scintillator detector array. The result, tau_mu = 2.197013(24) us, is in excellent agreement with the previous world average. The new world average tau_mu = 2.197019(21) us determines the Fermi constant G_F = 1.166371(6) x 10^-5 GeV^-2 (5 ppm). Additionally, the precision measurement of the positive muon lifetime is needed to determine the nucleon pseudoscalar coupling g_P.Comment: As published version (PRL, July 2007

Compliance to Bleach Disinfection Protocols among Injecting Drug Users in Miami

Bleach cleansing of injection equipment has been recommended to reduce the risk of human immunodeficiency virus (HIV) transmission associated with the reuse of injection equipment by injecting drug users (IDUs). We evaluated the recall and performance of the most commonly recommended bleach cleansing procedure of two complete fillings of the syringe with bleach, followed by two complete fillings with rinse water, and not putting used bleach and water back into source containers. IDUs were taught this procedure on enrollment in an HIV prevention demonstration project in Dade County, Florida. During follow-up session 6-12 months after initial training, the knowledge and ability of IDUs to perform bleach cleansing were assessed by trained observers using a standardized method. In 1988-90, we assessed the knowledge and ability of 450 IDUs to perform the bleach cleansing procedure taught at enrollment. More than 90% of IDUs assessed performed the basic steps. However, only 43.1% completely filled the syringe with bleach and only 35.8% completely filled the syringe with bleach at least twice. Substantial proportions of IDUs did not perform all the steps of the previously taught bleach cleansing procedure. Compliance decreased as the number of steps required was increased. This limited compliance may make bleach cleansing less effective and suggests that some IDUs may fail to adequately disinfect injection equipment and therefore sterile needles and syringes are safer than bleach-cleansed ones. Compliance testing can help assess the effectiveness of HIV prevention programs. © 1994 Raven Press, Ltd., New York