Tepary (Phaseolus actifolius Gray) beans perform better than common beans (Phaseolus vulgaris) under drought conditions. The mechanism of drought tolerance in tepary bean seedlings was explored by determining the water potential (WP), osmotic potential (OP), relative water content (RWC), free sugar concentration, and the level of K ion within the expanding leaves. Two week old tepary bean seedlings were subjected to a gradual water stress with sorbitol solutions exhibiting OP values of -0.19 MPa and -0.47 MPa. Turgor remained constant whereas WP, OP and RWC declined following the stress treatment. Osmotic adjustment (OA) occurred in each treatment but the contribution of sucrose and fructose was minor. Some sorbitol was translocated to leaves and contributed to OA. The decrease of K ions in leaves indicated that these ions did not contribute to the OA. A significant decrease in cell size was observed as determined by decrease in TW/DW ratio.

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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).

Leung Chun-wah. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2000. / Includes bibliographical references (leaves 113-122). / Abstracts in English and Chinese. / Thesis committee --- p.i / Statement --- p.ii / Acknowledgment --- p.iii / Abstract --- p.v / Table of contents --- p.ix / List of abbreviations --- p.xiv / List of figures --- p.xvii / List of tables --- p.xix / Chapter 1 --- LITERATURE REVIEW --- p.1 / Chapter 1.1 --- Introduction --- p.1 / Chapter 1.2 --- Artificial sweeteners --- p.3 / Chapter 1.2.1 --- SACCHARIN --- p.3 / Chapter 1.2.2 --- cyclamate --- p.4 / Chapter 1.2.3 --- Aspartame --- p.4 / Chapter 1.2.4 --- acesulfame-k --- p.5 / Chapter 1.2.5 --- SUCRALOSE --- p.5 / Chapter 1.3 --- natural sweet plant proteins --- p.7 / Chapter 1.3.1 --- THAUMATIN --- p.7 / Chapter 1.3.2 --- MONELLIN --- p.10 / Chapter 1.3.3 --- CURCULIN --- p.11 / Chapter 1.3.4 --- PENTADIN AND BRAZZEIN --- p.11 / Chapter 1.3.5 --- MIRACULIN --- p.12 / Chapter 1.3.6 --- MABINLIN --- p.12 / Chapter 1.4 --- Genetic Engineering of Sweet Plant Protein --- p.19 / Chapter 1.4.1 --- biotechnological studies on thaumatin --- p.20 / Chapter 1.4.1.1 --- Protein modification and sweetness --- p.20 / Chapter 1.4.1.2 --- Transgenic expression in microbes --- p.21 / Chapter 1.4.1.3 --- Transgenic expression in higher plants --- p.23 / Chapter 1.4.2 --- BIOTECHNOLOGICAL STUDIES ON MONELLIN --- p.24 / Chapter 1.4.2.1 --- Gene modification and transgenic expression in microbes --- p.24 / Chapter 1.4.2.2 --- Transgenic expression in plants --- p.25 / Chapter 1.4.3 --- TRANSGENIC EXPRESSION OF MABINLIN IN PLANTS --- p.26 / Chapter 1.5 --- phaseolin and its regulatory sequences --- p.27 / Chapter 1.6 --- ARABIDOPSIS --- p.29 / Chapter 1.6.1 --- ARABIDOPSIS THALIANA as a model plant --- p.29 / Chapter 1.6.2 --- Transformation methods --- p.29 / Chapter 1.6.2.1 --- Direct DNA uptake --- p.30 / Chapter 1.6.2.2 --- Agrobacterium-mediated transformation --- p.31 / Chapter 1.6.2.3 --- In planta transformation --- p.31 / Chapter 2 --- GENKRAL INTRODUTION AND HYPOTHESIS --- p.22 / Chapter 2.1 --- General Introduction --- p.33 / Chapter 2.2 --- Hypothesis --- p.34 / Chapter 3 --- MOLECULAR STUDIES ON SWEET PROTEIN MARINLIN : THERMAL STABILITY --- p.28 / Chapter 3.1 --- Introduction --- p.38 / Chapter 3.2 --- Materials --- p.40 / Chapter 3.2.1 --- laboratory wares --- p.40 / Chapter 3.2.2 --- Equipments --- p.40 / Chapter 3.2.3 --- Chemicals --- p.40 / Chapter 3.2.4 --- commerical kits --- p.41 / Chapter 3.2.5 --- DNA primers --- p.42 / Chapter 3.2.6 --- DNA plasmids --- p.43 / Chapter 3.2.7 --- bacterial strains --- p.43 / Chapter 3.2.8 --- Plant materials --- p.44 / Chapter 3.2.9 --- Protein and Antibody --- p.44 / Chapter 3.3 --- Methods --- p.45 / Chapter 3.3.1 --- Transformation of Arabidopsis with mbliii and mbli genes --- p.45 / Chapter 3.3.1.1 --- Construction of mutant MBLIII and MBLI genes containing single codon mutation by megaprimer PCR --- p.45 / Chapter 3.3.1.2 --- Cloning of PCR-amplified MBLIII and MBLI cDNAs into vector pD3-8 --- p.48 / Chapter 3.3.1.3 --- In vitro site-directed mutagensis (for the construction of MBLIII and MBLI cDNAs containing single codon mutation) --- p.49 / Chapter 3.3.1.4 --- Cloning of the wild-type and mutated MBLIII and MBLI cDNA into vector pTZ / phas --- p.53 / Chapter 3.3.1.5 --- Confirmation of sequence fidelity and mutated codon in MBLIII and MBLI cDNA by DNA sequencing --- p.53 / Chapter 3.3.1.6 --- Transfer of wild-type MBLIII and MBLI cDNA flanked by phaseolin regulatory sequence into Agrobacterium binary vector --- p.55 / Chapter 3.3.1.7 --- Transformation of Agrobacterium with pBI / phas / MBLIII and pBI / phas / MBLI chimeric gene constructs --- p.57 / Chapter 3.3.1.8 --- Vacuum infiltration transformation of A rabidopsis --- p.58 / Chapter 3.3.1.9 --- Screening of homozygous transgenic Arabidopsis --- p.59 / Chapter 3.3.2 --- Expression analysis of MBLIII transgene --- p.61 / Chapter 3.3.2.1 --- GUS assay of transgenic plants --- p.61 / Chapter 3.3.2.2 --- Genomic DNA isolation from transgenic plants --- p.61 / Chapter 3.3.2.3 --- PCR amplification of transgene --- p.62 / Chapter 3.3.2.4 --- Total RNA isolation from transgenic Arabidopsis --- p.63 / Chapter 3.3.2.5 --- RT-PCR of total RNA from transgenic Arabidopsis --- p.64 / Chapter 3.3.2.6 --- Verification of the presence of mutagenic site and the fidelity of RNA transcript from transgenic Arabidopsis --- p.65 / Chapter 3.3.2.7 --- Protein extraction and tricine SDS-PAGE of putative transgenic protein from Arabidopsis --- p.65 / Chapter 3.3.2.8 --- N-terminal amino acid sequencing --- p.66 / Chapter 3.3.2.9 --- Isoelectric precipitation of MBL --- p.67 / Chapter 3.3.2.10 --- Production of polyclonal antibody against purified MBL --- p.67 / Chapter 3.3.2.11 --- Western-blotting and immunodectection of Arabidopsis protein by anti-MBL polyclonal antibody --- p.69 / Chapter 3.4 --- results & discussion --- p.71 / Chapter 3.4.1 --- Site-specific mutations of Arginine residue in mbliii cdna and glutamine in mbli cdna --- p.71 / Chapter 3.4.1.1 --- Megaprimer PCR --- p.71 / Chapter 3.4.1.2 --- Cloning into the seed-specific expression vector pD38 --- p.74 / Chapter 3.4.1.3 --- In vitro site-directed mutagenesis --- p.76 / Chapter 3.4.2 --- Construction of plant expression vectors containing chimeric MBLIII and MBLI --- p.80 / Chapter 3.4.2.1 --- Cloning of MBLIII and MBLI cDNAs into the seed-specific expression vector pTZ / phas --- p.80 / Chapter 3.4.2.2 --- Cloning into the plant expression vector pBI121 --- p.83 / Chapter 3.4.3 --- Generation of homozygous transgenic Arabidopsis --- p.84 / Chapter 3.4.3.1 --- Screening of transgenic R1 Arabidopsis --- p.84 / Chapter 3.4.3.2 --- Screening of transgenic R2 plants --- p.86 / Chapter 3.4.3.3 --- Screening of homozygous R3 transgenic plants --- p.88 / Chapter 3.4.4 --- Detection of MBLIII transgene in Arabidopsis --- p.89 / Chapter 3.4.4.1 --- Gus Assay --- p.89 / Chapter 3.4.4.2 --- Detection of transgene integration --- p.90 / Chapter 3.4.5 --- DETECTION of MBLIII TRANSCRIPT IN TRANSGENIC arabidopsis --- p.92 / Chapter 3.4.5.1 --- RT-PCR (Reverse-transcription polymerase chain reaction) --- p.92 / Chapter 3.4.5.2 --- Verification of the presence of the mutant codon and sequence fidelity of the RT-PCR product --- p.94 / Chapter 3.4.6 --- DETECTION OF MBL III PROTEIN IN TRANSGENIC arabidopsis --- p.97 / Chapter 3.4.6.1 --- Expression of MBL protein --- p.97 / Chapter 3.4.6.2 --- Isoelectric precipitation --- p.101 / Chapter 3.4.6.3 --- Assay of titers and quality of primary polyclonal antibody against purified MBL protein --- p.103 / Chapter 3.4.6.4 --- Western blot / Immunodetection --- p.106 / Chapter 4 --- GENERAL DISCUSSION --- p.109 / Conclusion --- p.112 / References --- p.113

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