[No abstract available] / Science, Faculty of / Botany, Department of / Graduate

No description available.

In this thesis is described the characterisation of two morphogenesis mutants of Arabidopsis thaliana, with the aim of furthering our understanding of signalling in development. A thorough phenotypic analysis of both mutants is presented, with particular attention paid to the seedling root. The results of genetic analysis of hydra2 are also presented. The hydra mutants are characterised by a pleiotropic phenotype, with defective embryonic and seedling cell patterning, morphogenesis and root growth. The HYDRA1 gene encodes a A8-A7 sterol isomerase, while HYDRA2 encodes a sterol C14 reductase, previously identified as the FACKEL gene product. Seedlings mutant for each gene are similarly defective in the concentrations of the three major Arabidopsis sterols. Reporter gene analysis showed mis-expression of the hormonally-regulated DR5, IAA2 and ACSl promoters and of the epidermal cell file-specific GL2 promoter in the mutants. The mutants also exhibit enhanced responses to auxin. The phenotypes can be partially rescued by inhibition of auxin and ethylene signalling, but not by exogenous brassinosteroids. Evidence of abnormal activity of hormone-related membrane-bounds proteins and of altered membrane permeability to auxin is presented. A model in which correct sterol profiles are required for regulated auxin and ethylene signalling through effects on membrane function is proposed.

The polarization of exocytosis in yeast and animals is assisted by the exocyst - an octameric vesicle tethering complex and an effector of Rab and Rho GTPases. Recently, the exocyst was described as a functional complex involved in morphogenesis also in plants. Hála et al. (2008) described involvement of exocyst complex in pollen tube growth and hypocotyls elongation in dark grown seedlings, Fendrych et al. (2010) uncovered key role of exocyst in cell plate formation, Kulich et al. (2010) emphasized the participation of exocyst in seed coat generation and Pečenková et al. (2011) described the contribution of exocyst subunits in plant defense towards the pathogens. All these processes are intimately linked to polarized secretion. Here we show involvement of exocyst in auxin efflux carriers PINs recycling. Using direct auxin transport measurement and GFP-tagged proteins, we showed that the exocyst is involved in recycling and polarization of PIN proteins and polar auxin transport regulation. Rootward polar auxin transport is compromised in loss-of-function mutants in exocyst subunits EXO70A1. On the cellular level we have detected small portion of PIN2:GFP in the "BFA-like" FM4-64 labelled compartments distinct from VHAa1 labeled endosoms. Moreover recycling of PIN1 and PIN2 is retarded in roots of...

No description available.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1955. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves [47]-52).

Thesis--University of Michigan. / "Contribution from the Department of Botany, University of Michigan, no. 850." "Reprinted from the American journal of botany, vol. 35, no. 3 ... March, 1948."

Thesis (PH. D.)--University of Michigan, 1942. / Caption title. Thesis note on label mounted on p. [217]. "Reprinted from the Proceedings of the National Academy of Sciences, vol. 28, no. 6 ... June, 1942." Bibliography: p. 228.

No description available.

No description available.