No description available.

No description available.

Cyclic nucleotide, cAMP, is an important signaling molecule in animals and plants. However, in plants the enzymes that synthesize this second messenger, adenyl cyclases (ACs), remain elusive. Given the physiological importance of cAMP in signaling, particularly in response to biotic and abiotic stresses, it is thus important to identify and characterize ACs in higher plants. Using computational approaches, a disease resistance protein from Arabidopsis thaliana, At3g04220 was found to have an AC catalytic center motif. In an attempt to prove that this candidate has adenyl cyclases activity in vitro, the coding sequence of the putative AC catalytic domain of this protein was cloned and expressed in E. coli and the recombinant protein was purified. The nucleotide cyclase activity of the recombinant protein was examined using cyclic nucleotide enzyme immunoassays. In parallel, the expression of At3g04220 was measured in leaves under three different stress conditions in order to determine under which conditions the disease resistance protein could function. Results show that the purified recombinant protein has Mn2+ dependent AC activity in vitro, and the expression analysis supports a role for At3g04220 and cAMP in plant defense.

Thesis (Ph. D.)--University of Queensland, 2003. / Includes bibliographical references.

Thesis (Ph. D.)--Washington State University, December 2008. / Title from PDF title page (viewed on July 10, 2009). "School of Molecular Biosciences." Includes bibliographical references.

published_or_final_version / Biological Sciences / Doctoral / Doctor of Philosophy

Streptomycin resistance in E. coli ribosomes is conferred by alterations in the amino acid sequence of 30S ribosomal protein S12. The alterations result from point mutations at specific locations in the rps12 gene. A point mutation at a conserved nucleotide in the 16S rRNA gene, originally identified in Euglena gracilis chloroplasts, also confers streptomycin resistance to prokaryotic-like ribosomes. The Nicotiana tabacum mutant "SR1" possesses a chloroplast-linked streptomycin resistance allele. The results presented in this thesis identify a mutation in SR116S rRNA, which occurs at the same position as in streptomycin resistant Euglena mutants. The tobacco chloroplast rps12 gene has been characterized. This gene is expressed in a unique way; two separate transcripts encoding different portions of the gene undergo a bimolecular (trans-) splicing event during mRNA maturation. C-terminal rps12 exons 2 and 3 were identified in the inverted repeat regions of the tobacco chloroplast genome. Complementary DNA sequencing of mature rps12 mRNA allowed deduction of the remaining N-terminal (exon 1) sequence. Hybridizations with synthetic oligodeoxyribonucleotide primers complementary to the deduced RNA sequence located the coding region of exon 1 to be 29 kilobasepairs (kbp) downstream of the nearest copy, and 69 kbp away from, and on the opposite DNA strand of, the distal copy, of exons 2 and 3. Northern hybridization analysis and primer extension sequencing of cDNA of rps12 transcripts indicate that exon 1 and exons 2-3 are encoded on separate transcripts. Exon 1 and exons 2-3 are covalently ligated in mature rps12 mRNA. Therefore, the separate transcripts encoding exon 1 and exons 2-3 undergo a trans-splicing event during the maturation of rps12 mRNA. A complete cloned library of tobacco chloroplast DNA was obtained, consisting of overlapping Bam HI restriction fragments. Three new restriction maps of tobacco chloroplast DNA, for the enzymes Sma I, Kpn I, and Bam HI, were derived by two-dimensional gel analysis and a novel computer-aided mapping technique.

Plants in the field are exposed to multiple stresses and their response to these various stresses determines their capacity to survive. Plants can use multiple signaling pathways and signals to mediate their response / for example, at least four different signal pathways have been identified for water-deficit stress (Shinozaki and Yamaguchi-Shinozaki, 1997 / Xiong et al., 2002). Different forms of stress may activate or utilize the same components, including proteins and other signaling molecules. Signaling molecules such as jasmonic acid (JA) are involved in multiple stress response and development in plants (Creelman and Mullet, 1995, 1997 / Turner et al., 2002). However it is the specific combination of various components of the signaling network coupled with spatial and temporal factors that allows the plant to mount a directed response to any given stress factors. Systemic defense responses thus provide an attractive model for the study of cell-to-to cell signal transduction pathways that operates over long distances (Lucas and Lee, 2004).<br /> <br /> Cellular and physiological evidence suggest the presence of a novel class of systemic mobile plant molecule that is recognized by antibodies against vertebrate atrial natriuretic peptides (ANPs). It has been demonstrated that a recombinant Arabidopsis thaliana natriuretic peptide analogue (AtPNP-A) molecule can induce osmoticumdependent water uptake into protoplast at nanomolar concentrations thus affecting cell volume and hence plant growth. In this study we confirm that active recombinant protein causes swelling in Arabidopsis mesophyll cell protoplasts (MCPs).

Thesis (Ph. D.)--University of Hong Kong, 2010. / Includes bibliographical references. Also available in print.

Plants in the field are exposed to multiple stresses and their response to these various stresses determines their capacity to survive. Plants can use multiple signaling pathways and signals to mediate their response / for example, at least four different signal pathways have been identified for water-deficit stress (Shinozaki and Yamaguchi-Shinozaki, 1997 / Xiong et al., 2002). Different forms of stress may activate or utilize the same components, including proteins and other signaling molecules. Signaling molecules such as jasmonic acid (JA) are involved in multiple stress response and development in plants (Creelman and Mullet, 1995, 1997 / Turner et al., 2002). However it is the specific combination of various components of the signaling network coupled with spatial and temporal factors that allows the plant to mount a directed response to any given stress factors. Systemic defense responses thus provide an attractive model for the study of cell-to-to cell signal transduction pathways that operates over long distances (Lucas and Lee, 2004).<br /> <br /> Cellular and physiological evidence suggest the presence of a novel class of systemic mobile plant molecule that is recognized by antibodies against vertebrate atrial natriuretic peptides (ANPs). It has been demonstrated that a recombinant Arabidopsis thaliana natriuretic peptide analogue (AtPNP-A) molecule can induce osmoticumdependent water uptake into protoplast at nanomolar concentrations thus affecting cell volume and hence plant growth. In this study we confirm that active recombinant protein causes swelling in Arabidopsis mesophyll cell protoplasts (MCPs).