Abstract: "Let G [superset of] H be Lie groups, g [superset of] h their Lie algebras, and pr : g* -> h* the natural projection. For coadjoint orbits O[superscript G] [subset of] g* and O[superscript H] [subset of] h*, we denote by n(O[superscript G], O[superscript H]) the number of H-orbits in the intersection O[superscript G] [intersection of]pr[superscript -1](O[superscript H]. In the spirit of the orbit method due to Kirillov and Kostant, one expects that n(O[superscript G], O[superscript H]) coincides with the multiplicity of [tau][element of] Ĥ occurring in the restriction [pi]/[subscript H] if [pi][element of]Ĝ is 'attached' to O[superscript G] and [tau] [element of] Ĥ is 'attached' to O[superscript H]. Such a result is known for nilpotent Lie groups and certain solvable groups, however, very few attempts have been made so far for semisimple Lie groups. In this paper, we give a sufficient condition on O[superscript G] so that n(O[superscript G], O[superscript H] [
Abstract: "Let G [superset of] H be Lie groups, g [superset of] h their Lie algebras, and pr : g* -> h* the natural projection.
Plant development and survival depend on the ability of these organisms to integrate many signalling which enables them to produce an appropriate response. Ethylene and auxin are phytohormones known to regulate agonistly or antagonistly many processes of plant development but yet the key integrating molecular players remain largely undiscovered. My Ph.D project deals with the identification and characterization of molecular actors that take part in this dialogue. We report that Sl-IAA3, a member of the tomato auxin/indole-3-acetic acid (Aux/IAA) gene family, is an intersection point between auxin and ethylene signal transduction pathways. Aux/IAA genes encode short-lived transcriptional regulators that mediate auxin responses. Sl-IAA3 expression is controlled by both auxin and ethylene and is regulated on a tight tissue-specific basis. Downregulation of Sl-IAA3 via an antisense strategy results in auxin and ethylenerelated phenotypes including altered apical dominance, lower auxin sensitivity, exaggerated apical hook curvature in the dark and reduced petiole epinasty in the light. These ethylene-related phenotypes in the antisense tomato lines (AS-IAA3) position Sl-IAA3 firmly at the crossroads between auxin and ethylene signalling in tomato. The induction of apical hook offers an excellent system to study auxinethylene interplay. In Arabidopsis, ethylene acts through HOOKLESS (HLS1) to control hook formation through modulating differential cell elongation in opposite sides of the hook. Loss of function mutation in the HLS1 gene results in the absence of hook even in the presence of exogenous ethylene. In the present study, we extended the phenotypes of the Arabidopsis hls1 mutant to alteration of light sensitivity, glucose and ABA tolerance and gravitropic growth thus uncovering the importance of HLS gene in the integration of multiple signalling pathways. Two functional tomato hookless genes (Sl-HLS1 and Sl-HLS2) were isolated in this study and shown to positively complement the Arabidopsis hls1 mutant. Expression of Sl-HLS2 in the hook is restricted to the outer face, opposite to Sl-IAA3 whose expression is localized in the inner face of the hook curvature. The data suggest that Sl-HLS2 and Sl-IAA3 exert antagonist control of cell elongation in the inner and outer part of the apical hook. Overall, the two genes characterized in this study open new prospects towards addressing the role of ethylene and auxin cross-talk during fruit development and ripening.
Plant development and survival depend on the ability of these organisms to integrate many signalling which enables them to produce an appropriate response.
Carboxysomes are polyhedral microcompartments found in all cyanobacteria and in many chemoautotrophs. Within their shell they contain the enzyme ribulose-1, 5-bisphosphate carboxylase/oxygenase (RubisCO), which fixes CO2. Downstream of the carboxysome operon there is another gene cluster containing several genes that may enhance carboxysome function. Two of these genes, cbbQ and cbbO, encode potential RubisCO activases. Using recombinant CbbQ and CbbO protein, and RubisCO isolated from carboxysomes the interaction between these proteins was studied. The CbbO and CbbQ proteins were both His tagged, allowing them to be purified with Ni2+-NTA column chromatography. Each of these tagged proteins was incubated with RubisCO on a Ni2+-NTA column to determine if both proteins could be co-eluted. These studies suggest that recombinant CbbO and CbbQ do not interact individually with RubisCO. Since His-tagged CbbO and untagged CbbQ, when co-expressed in E. coli, form a complex, ongoing studies are focused on determining if both potential activases are needed to interact with RubisCO when co-expressed. --Page iv.
Carboxysomes are polyhedral microcompartments found in all cyanobacteria and in many chemoautotrophs.
