J. Sakaguchi

Hyperfine structure of antiprotonic helium revealed by a laser-microwave-laser resonance method.

Using a newly developed laser-microwave-laser resonance method, we observed a pair of microwave transitions between hyperfine levels of the (n,L)=(37,35) state of antiprotonic helium. This experiment confirms the quadruplet hyperfine structure arising from the interaction of the antiproton orbital angular momentum, the electron spin and the antiproton spin as predicted by Bakalov and Korobov. The measured frequencies of nu(+)(HF)=12.895 96+/-0.000 34 GHz and nu(-)(HF)=12.924 67+/-0.000 29 GHz agree with recent theoretical calculations on a level of 6x10(-5).

miR165/166 and the development of land plants

In the developmental process of plant cells, cell fate is determined by expression of specific genes. Their expressions are directed by specific transcriptional regulators and positional signals that convey the locations of respective cells along various body axes, including proximal–distal, adaxial–abaxial and medial–lateral axes. Recently it was reported that some small regulatory RNAs work in a non‐cell‐autonomous fashion and provide neighboring cells with positional signals. Among such small RNAs, we will review unique biological features of microRNA 165/166 widely involved in plant development.

Cell differentiation in the longitudinal veins and formation of commissural veins in rice (Oryza sativa) and maize (Zea mays)

Vascular development is a central theme in plant science. However, little is known about the mechanism of vascular development in monocotyledons (compared with dicotyledons). Therefore, we investigated sequential processes of differentiation into various different vascular cells by carrying out detailed observations using serial sections of the bases of developing leaves of rice and maize. The developmental process of the longitudinal vascular bundles was divided into six stages in rice and five stages in maize. The initiation of differentiation into procambial progenitor cells forming the commissural vein arose in a circular layer cell that was adjacent to both a metaxylem vessel and one or a few phloem cells in stage V longitudinal vascular bundles. In most cases the differentiation of ground meristem cells into procambial progenitor cells extended in one direction, toward the next longitudinal vascular bundle, and subsequent periclinal divisions and further differentiation produced a vessel element, two companion cells and a sieve element to form a commissural vein. These results suggest the presence of an intercellular signal(s) that induces differentiation of the circular layer cell and the ground meristem cells into procambial progenitor cells, forming a commissural vein sequentially.

COE1, an LRR-RLK responsible for commissural vein pattern formation in rice.

Leaf veins have a complex network pattern. Formation of this vein pattern has been widely studied as a model of tissue pattern formation in plants. To understand the molecular mechanism governing the vascular patterning process, we isolated the rice mutant, commissural vein excessive1 (coe1). The coe1 mutants had short commissural vein (CV) intervals and produced clustered CVs. Application of 1-N-naphthylphthalamic acid and brefeldin A decreased CV intervals, and application of 1-naphthaleneacetic acid increased CV intervals in wild-type rice; however, coe1 mutants were insensitive to these chemicals. COE1 encodes a leucine-rich repeat receptor-like kinase, whose amino acid sequence is similar to that of brassinosteroid-insensitive 1-associated receptor kinase 1 (BAK1), and which is localized at the plasma membrane. Because of the sequence similarity of COE1 to BAK1, we also examined the involvement of brassinosteroids in CV formation. Brassinolide, an active brassinosteroid, decreased the CV intervals of wild-type rice, and brassinazole, an inhibitor of brassinosteroid biosynthesis, increased the CV intervals of wild-type rice, but coe1 mutants showed insensitivity to these chemicals. These results suggest that auxin and brassinosteroids regulate CV intervals in opposite directions, and COE1 may regulate CV intervals downstream of auxin and brassinosteroid signals.

Systematic study of the decay rates of antiprotonic helium states

A systematic study of the decay rates of antiprotonic helium (p{sup 4}He{sup +} and p{sup 3}He{sup +}) at CERN Antiproton Decelerator has been made by a laser spectroscopic method. The decay rates of some of its short-lived states, namely those for which the Auger rates {gamma}{sub A} are much larger than their radiative decay rates ({gamma}{sub rad}{approx}1 {mu}s{sup -1}), were determined from the time distributions of the antiproton annihilation signals induced by laser beams, and the widths of the atomic resonance lines. The magnitude of the decay rates, especially their relation with the transition multipolarity, is discussed and compared with theoretical calculations.

Hyperfine Structure Measurements of Antiprotonic Helium and Antihydrogen

This paper describes measurements of the hyperfine structure of two antiprotonic atoms that are planned at the Antiproton Decelerator (AD) at CERN. The first part deals with antiprotonic helium, a three-body system of α-particle, antiproton and electron that was previously studied at LEAR. A measurement will test existing three-body calculations and may— through comparison with these theories— determine the magnetic moment \( \mu _{\overline {\text{p}} } \) of the antiproton more precisely than currently available, thus providing a test of CPT invariance. The second system, antihydrogen, consisting of an antiproton and apositron, is planned to be produced at thermal energies at the AD. A measurement of the ground-state hyperfine splitting \( v_{{\text{HF}}} \left( {\overline {\text{H}} } \right) \) , which for hydrogen is one of the most accurately measuredp hysical quantities, will directly yielda precise value for \( \mu _{\overline {\text{p}} } \) , andalso compare the internal structure of proton andan tiproton through the contribution of the magnetic size of the \( \overline {\text{p}} {\mathbf{ }}{\text{to}}{\mathbf{ }}\nu _{{\text{HF}}} \left( {\overline {\text{H}} } \right) \) .

Light perception in aerial tissues enhances DWF4 accumulation in root tips and induces root growth

Many attempts have been made to characterize the activities of brassinosteroids (BRs), which are important plant hormones. The crosstalk between light perception and the BR signalling pathway has been extensively studied regarding its effects on photomorphogenesis, especially in elongating etiolated hypocotyls. In contrast, how and where the light induces BR biosynthesis remain uncharacterized. DWF4 is one of the main enzymes involved in the BR biosynthesis pathway in Arabidopsis thaliana. We established DWF4-GUS A. thaliana lines in a homozygous dwf4-102 genetic background, but functionally complemented with a genomic DWF4 sequence fused in-frame with a β-glucuronidase (GUS) marker gene. The DWF4-GUS plants enabled the visualization of the accumulation of DWF4 under different conditions. We investigated the effects of aboveground light on root and hypocotyl growth. We observed that root length increased when shoots were maintained under light irrespective of whether roots were exposed to light. We also determined that light perception in aerial tissues enhanced DWF4 accumulation in the root tips. Overall, our data indicate that BR biosynthesis is promoted in the root tip regions by an unknown mechanism in distantly located shoot tissues exposed to light, leading to increased root growth.

Precise laser spectroscopy of the antiprotonic helium atom and CPT test on antiproton mass and charge

Abstract We have measured twelve transition frequencies of the antiprotonic helium atom (pHe + ) with precisions of 0.1–0.2 ppm using a laser spectroscopic method. The agreement between the experiment and theories was so good that we can put a limit on the proton-antiproton mass (or charge) difference. The new limit is expected to be much smaller than the already published value, 60 ppb (6 × 10 −8 ).

First observation of the hyperfine and superhyperfine structure of antiprotonic helium by laser-microwave spectroscopy

Abstract We have designed and developed a laser-microwave triple resonance spectroscopy experiment of antiprotonic helium to investigate its hyperfine (HF) and superhyperfine (SHF) structures. We succeeded in making microwave transitions between HF substates of the ( n , l ) = (37, 35) metastable state, and resolved doublet resonance peaks split by SHFS. We determined the resonance frequencies with 30ppm precision. The experimental values agree with recent theoretical calculations, and to ∼ 60ppm level three-body QED theory is verified.