Ectopic expression of the HAM59 gene causes homeotic transformations of reproductive organs in sunflower (Helianthus annuus L.).

The function of the HAM59 MADS-box gene in sunflower (Helianthus annuus L.) was studied to clarify homeotic C activity in the Asteraceae plant family. For the first time, transgenic sunflower plants with a modified pattern of HAM59 expression were obtained. It was shown that the HAM59 MADS-box transcription factor did mediate C activity in sunflower. In particular, it participated in termination of the floral meristem, repression of the cadastral function of A-activity, and together with other C-type sunflower protein HAM45-in the specification of the identity of stamens and pistils.

Experimental constraints on left-right symmetric models from muon decay.

The TWIST Collaboration has completed a new measurement of the energy-angle spectrum of positrons from the decay of highly polarized muons. A simultaneous measurement of the muon decay parameters ρ, δ, and P(µ)(π)ξ tests the standard model in a purely leptonic process and provides improved limits for relevant extensions to the standard model. Specifically, for the generalized left-right symmetric model |(g(R)/g(L))ζ|<0.020 and (g(L)/g(R))m(2)>578 GeV/c(2), both 90% C.L.

[Induction, regeneration, and biolistic sensitivity of different genotypes of common wheat (Triticum aestivum L.)].

The induction, regeneration, and biolistic sensitivities of different genotypes of common wheat (Triticum aestivum L.) have been determined in order to develop an efficient system for transformation of Russian cultivars of spring wheat. Short-term (two days) cold treatment (4 degrees C) has been demonstrated to distinctly increase the frequency of morphogenetic callus induction. The optimal phytohormonal composition of the nutrient medium ensuring an in vitro regeneration rate of the common wheat cultivar Lada as high as 90% has been determined. The optimal temporal parameters of genetic transformation of wheat plants (10-14 days of culturing after initiation of a morphogenetic callus) have been determined for two transformation methods: biolistic without precipitated DNA and transformation with the plasmid psGFP-BAR. Analysis of the transient expression of the gfp gene has confirmed that 14 days of culturing is the optimal duration.

[Sugar beet (Beta vulgaris L.) morphogenesis in vitro: effects of phytohormone type and concentration in the culture medium, type of explants, and plant genotype on shoot regeneration frequency].

In vitro regeneration techniques have been optimized for seven strains and cultivars of sugar beet (Beta vulgaris L.) bred in Russia. The frequency of shoot regeneration from somatic cells and tissues of sugar beet varies from 10 to 97% depending on the explant type, culture-medium composition, and genotype. The in vitro regeneration potential has been estimated in plants with different genotypes. The effect of medium composition (phytohormones and carbohydrates) on the frequency of the formation of a morphogenic callus competent for plant regeneration has been determined. The effect of the types and concentrations of various cytokines (zeatin, kinetin, and 6-benzylaminopurine) on direct shoot regeneration from cotyledon nodes has been estimated. The culture-medium composition has been optimized for direct shoot regeneration from petioles. The effects of different concentrations of abscisic acid on the frequency of shoot regeneration from a morphogenic callus has been studied. Micropropagation has been used to obtain petiole explants and reproduce the shoots obtained by direct regeneration from cotyledon nodes, petioles, and calluses. Improved shoot-regeneration methods can be used for both agrobacterial and bioballistic genetic transformation of the sugar beet genotypes studied.

Measurement of the Michel parameter rho in muon decay.

The TWIST Collaboration has measured the Michel parameter rho in normal muon decay, mu(+)--> e(+)nu(e)nu (mu). In the standard model, rho = 3/4. Deviations from this value imply mixing of left- and right-handed muon and electron couplings. We find rho=0.750 80+/-0.000 32(stat) +/- 0.000 97(syst) +/- 0.000 23, where the last uncertainty represents the dependence of rho on the Michel parameter eta. This result sets new limits on the W(L)-W(R) mixing angle in left-right symmetric models.