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Patricia Zambryski

Publications and source records attributed to Patricia Zambryski.

5 recordsLinked to original sources
PubMed2005

Predicted hexameric structure of the Agrobacterium VirB4 C terminus suggests VirB4 acts as a docking site during type IV secretion.

The Agrobacterium T-DNA transporter belongs to a growing class of evolutionarily conserved transporters, called type IV secretion systems (T4SSs). VirB4, 789 aa, is the largest T4SS component, providing a rich source of possible structural domains. Here, we use a variety of bioinformatics methods to predict that the C-terminal domain of VirB4 (including the Walker A and B nucleotide-binding motifs) is related by divergent evolution to the cytoplasmic domain of TrwB, the coupling protein required for conjugative transfer of plasmid R388 from Escherichia coli. This prediction is supported by detailed sequence and structure analyses showing conservation of functionally and structurally important residues between VirB4 and TrwB. The availability of a solved crystal structure for TrwB enables the construction of a comparative model for VirB4 and the prediction that, like TrwB, VirB4 forms a hexamer. These results lead to a model in which VirB4 acts as a docking site at the entrance of the T4SS channel and acts in concert with VirD4 and VirB11 to transport substrates (T-strand linked to VirD2 or proteins such as VirE2, VirE3, or VirF) through the T4SS.

Amino Acid Sequence↗
PubMed2004

The role of SEUSS in auxin response and floral organ patterning.

Genetic and physiological analyses implicate auxin flux in patterning, initiation and growth of floral organs. Within the Arabidopsis flower, the ETTIN/ARF3 transcription factor responds to auxin to effect perianth organ number and reproductive organ differentiation. This work describes a modifier of ettin that causes filamentous, mispositioned outer whorl organs and reduced numbers of malformed stamens in the double mutant. The modifier was discovered to be a new allele of the seuss (seu) mutant. SEU encodes a novel protein that is predicted to transcriptionally co-repress the AGAMOUS floral organ identity gene. The effects of seu on ett are shown to be independent of the SEU-AG pathway. Furthermore, morphological, physiological and genetic evidence implicate SEU in auxin-regulated growth and development. seu has a pleiotropic phenotype that includes reductions in several classic auxin responses such as apical dominance, lateral root initiation, sensitivity to exogenous auxin and activation of the DR5 auxin response reporter. seu displays a synergistic interaction with the auxin response mutant pinoid, producing flowers with few outer whorl organs. Collectively, these data suggest that SEU is a novel factor affecting auxin response. A model is proposed in which SEU functions jointly with ETT in auxin response to promote floral organ patterning and growth.

AGAMOUS Protein, Arabidopsis↗
PubMed2002

Leaf-to-shoot apex movement of symplastic tracer is restricted coincident with flowering in Arabidopsis.

Classical experiments in plant physiology showed that leaves are the source of signals that control the development of flowers from shoot meristems. Additional physiological and genetic experiments have indicated some of the molecules (e.g., gibberellins, cytokinins, and sucrose) that promote flowering in mustards including Arabidopsis. These small hydrophilic molecules are likely to move to the shoot apex symplastically via the phloem and/or via cell-to-cell movement through plasmodesmata. To analyze potential changes in the symplastic trafficking of small molecules during the induction of flowering in Arabidopsis, we measured changes in the flow of symplastic tracers from the leaf to the shoot apex. We previously found that the onset of flowering is coincident with an evident decrease in the leaf-to-shoot trafficking of symplastic tracer molecules; this decrease in trafficking is transitory and resumes when floral development is established. Here we provide detailed analyses of symplastic connectivity during floral induction by monitoring tracer movement under different photoperiodic induction conditions and in a number of genetic backgrounds with altered flowering times. In all cases, the correlation between flowering and the reduction of symplastic tracer movement holds true. The lack of tracer movement during the induction of flowering may represent a change in plasmodesmal selectivity at this time or that a period of reduced symplastic communication is associated with floral induction.

Arabidopsis↗