<p>The rapid localized cell death at and around sites of attempted pathogen infection, termed the hypersensitive response (HR), is an immune response mechanism commonly utilized in plants. This cell death limits pathogens from accessing host nutrients which often leads to resistance. The interaction of pathogen signals and host receptors that are required for the HR are well studied; however, the processes that regulate cell death during the HR remain enigmatic. The plant lesion mimic mutants, which form spontaneous lesions and/or undergo autoactive cell death in the absence of infection or stress, are commonly used as model systems to study the HR. Some lesion mimic mutants are caused by autoactive alleles of the resistance genes that recognize pathogen signals and trigger the HR. These mutants have facilitated studies of the HR as they allow the study of the HR without the need to control for pathogen infection. Currently, the etiologies of most maize lesion mimic mutants are unknown. Lesion mimic mutants contain numerous metabolic perturbations, including the increased accumulation of salicylic acid (SA), phenylalanine, and intermediates in heme and chlorophyll biosynthesis and catabolism. Some of these perturbations are dependent on the cause of lesion formation. As such, the accumulation of any of these metabolites in a lesion mutant may infer the etiology of that mutant. This dissertation contains three projects related to the molecular characterization of HR and maize lesion mimic mutants. In the first project (Chapter 2), I compared the metabolite profile of 23 maize lesion mimic mutants. This work identified two major findings that were further explored in the other projects in this dissertation. The first major finding is that four of the 23 mutants have metabolic perturbations that are like those of the known HR lesion mutant, <em>Rp1-D21</em>. In project two (Chapter 3), I molecularly characterize, <em>Lesion10</em>, which is one of the mutants that has HR-like metabolic perturbations. Using genome-wide association studies, I identified a gene candidate that may modify <em>Lesion10</em> phenotypic severity. The second major finding from project one is that SA accumulates to higher than wild-type levels in most of the lesion mutants analyzed. In the third project (Chapter 4), I characterized how SA is synthesized in maize and if SA is necessary or sufficient for the formation of lesions during the HR in maize. Using untargeted metabolite analysis, stable isotope feedings, and enzyme assays, I provide evidence of both known SA biosynthetic pathways in maize and demonstrate that the two pathways are interdependent. In addition, I show that increased accumulation of SA is not required for the HR in maize.</p>

Abiotic stresses like salinity, drought, and extreme temperature are constantly on the rise, posing a very high risk to global agricultural productivity and food security. Hence, understanding stress signaling pathways can help engineer plants that can better withstand stress in unfavorable conditions. The salicylic acid (SA) signaling pathway has been widely studied for its important role in mediating abiotic stress in plants. In tobacco plants, Salicylic Acid Binding Protein 2 (SABP2), a methyl esterase enzyme, catalyzes the conversion of methyl salicylate (MeSA) to SA, which triggers the defense response via the SA-mediated signaling pathway. SIP-428 (SABP2 Interacting Protein-428) is an NAD+ dependent SIR2-like (Silent Information Regulator) deacetylase enzyme that likely interacts with SABP2 during SA biosynthesis. In previous studies, SIP-428 has been shown to be a negative regulator of plant growth under abiotic stress (NaCl and mannitol in vivo). Reactive Oxygen Species (ROS) are oxidizing oxygen products that accumulate under stress conditions, and at high levels can be very harmful to plants. Antioxidant enzymes such as catalase (CAT), guaiacol peroxidase (POD), ascorbate peroxidase (APX), and superoxide dismutase (SOD) are actively involved in lowering the ROS levels in the cell by combating the oxidative stress. The objective of this study was to analyze the regulatory functions of SIP-428 in ROS signaling of tobacco plants through the biochemical quantification of POD and CAT activities. We investigated the SIP-428 RNAi-silenced tobacco plants for the POD and CAT enzyme activities in Osmotic (Mannitol) and Salinity (NaCl) stressed plants. Our results showed that SIP-428 plays a significant role in modulating antioxidant enzymes in stressed plants. This study has improved our understanding of some regulatory roles of SIP428, and its application can be used to enhance stress tolerance via the use of synthetic biology.

The main aim of this research is to provide a low cost and sustainable biochar for the removal of organic pollutants from aqueous solution. Wastewater pollution by organic contaminants of emerging concern has become a subject of intense discussion. Removing these contaminants from aqueous solution is paramount to improve water quality for both humans and animal consumption. Traditional adsorption techniques using activated carbon are universal and fast, however, they are very costly. This dissertation therefore seeks to find an alternative low cost adsorbent which can be used to adsorb contaminants from aqueous solution. In chapter one, an overview of some of the selected organic contaminants of emerging concern is given. Pharmaceutical and pesticide entry into the environment, their fate and ecotoxicity are highlighted. Available techniques for the removal of contaminants from aqueous solution are also given. Chapter two is a study on the adsorption of some selected pharmaceuticals using a fast pyrolysis low cost biochar produced from pinewood feedstocks. The pinewood biochar used as the adsorbent in this study was made by fast pyrolysis in an augered reactor at a temperature of 425 oC and a residence time of 20-30 s during bio-oil production. In chapter three, switchgrass biochar has been tested for its potential for remediating water that is contaminated with two phenoxy herbicides, 2,4-dichlorophenoxyacetic (2,4-D) acid and 2-methyl-4-chloro-phenoxyacetic acid (MCPA). The adsorption capacity was remarkable when compared to commercial activated carbon per unit of measured surface area. Furthermore, in chapter four, magnetic and non-magnetic low cost biochars have been tested for the removal of the herbicide metribuzin from aqueous solution under different experimental conditions. The magnetic biochar synthesized from raw switchgrass biochar does not show a detrimental effect on the adsorption capacity. Additional value of this magnetic biochar is the ease of separation from contaminated solution following adsorption.

A Araucaria angustifólia é uma conífera nativa do Brasil que apresenta sementes recalcitrantes. Devido a sua importância econômica, foi intensamente explorada ao longo dos anos, encontrando-se atualmente classificada como espécie em perigo crítico de extinção pela International Union for Conservation of Nature. A embriogênese somática apresenta-se como uma ferramenta biotecnológica de grande valia na propagação de espécies recalcitrantes e de difícil propagação, com aplicação em programas de conservação, reflorestamento, e melhoramento genético vegetal. Estudos comparativos dos processos de embriogênese somática e zigótica têm permitido o conhecimento dos fatores bioquímicos, fisiológicos e genéticos que controlam o desenvolvimento do embrião, e o estabelecimento as condições artificiais para o correto desenvolvimento embrionário in vitro. O objetivo deste trabalho foi estudar a participação do ácido salicílico como sinalizador do processo de embriogênese zigótica e somática em A. angustifólia. Para tanto foi determinado o conteúdo de ácido salicílico livre e conjugado ao longo da embriogênese zigótica, e o efeito de sua suplementação em culturas embriogênicas com diferentes potenciais para a maturação. Para a embriogênese somática, a presença do ácido salicílico foi correlacionada com a geração de óxido nítrico e espécies reativas de oxigênio , e com a expressão do gene \"Somatic Embryogenesis Receptor Kinase\" (AaSERK). Os resultados obtidos demonstram que: a) ocorre um maior conteúdo de ácido salicílico na forma livre e conjugada nas etapas iniciais da embriogênese zigótica; b) a suplementação de ácido salicílico, nas concentrações de 0,5 a 2 mM, inibiram a indução de culturas embriogênicas; c) culturas embriogênicas incubadas em ácido salicílico apresentaram redução da síntese endógena de espécies reativas de oxigênio e aumento no conteúdo de óxido nítrico; d) a redução de espécies reativas de oxigênio indicou uma relação dose dependente com o ácido salicílico; e) a adição de um doador de óxido nítrico e um sequestrador inibiram a produção de espécies reativas de oxigênio; f) a expressão do gene AaSERK atingiu o maior nível no período de quatro horas de incubação em 0,1 mM de AS / Araucaria angustifolia is a conifer native of Brazil with recalcitrant seeds. Due to its economic importance, the exploration has been extensively over the years, currently this specie is classified as critically endangered by the International Union for Conservation of Nature. Somatic embryogenesis is presented as a biotechnological tool of great value in the propagation of recalcitrant species and difficult to spread, with applications in conservation, reforestation programs, and plant breeding. Comparative studies of the processes of zygotic and somatic embryogenesis has allowed the knowledge of biochemical, physiological and genetic factors that control embryo development, and the establishment artificial conditions for proper embryonic development in vitro. The objective of this work was to study the role of salicylic acid as a marker of zygotic embryogenesis and somatic process in A. angustifolia. Thus, we determined the content of free salicylic acid and conjugated along the zygotic embryogenesis, and the effect of their supplementation with different potential embryogenic cultures for maturation. For somatic embryogenesis, the presence of salicylic acid was correlated with the generation of nitric oxide, reactive oxygen species and in the gene expression \"Somatic embryogenesis Receptor Kinase\" (AaSERK). The results show that: a) there is an increased content of salicylic acid in free and conjugated form in the initial stages of zygotic embryogenesis; b) salicylic acid supplementation, in concentrations from 0.5 to 2 mM, inhibited the induction of embryogenic cultures; c) embryos incubated in salicylic acid decreased endogenous synthesis of reactive oxygen species and increase in content of nitric oxide; d) the reduction of reactive oxygen species indicated a dose-dependent relationship with salicylic acid; e) the addition of a nitric oxide donor and a kidnapper inhibited the production of reactive oxygen species; f) the expression of the gene AaSERK reached the highest level in four hours of incubation in 0.1 mM AS

A interacao planta-patogeno desencadeia uma serie de sinais que ainda nao estao completamente elucidados. Uma das respostas e a reacao de hipersensibilidade (RH), onde ocorre a morte celular programada no sitio da infeccao, impedindo a proliferacao do patogeno. Acredita que a morte celular e provocada pelo aumento do ERO, principalmente peroxido de hidrogenio (H2O2) e com o acumulo de acido salicilico (AS) que inibe a catalase, enzima responsavel pela transformacao de H2O2 em H2O e O2. Alem disso, ocorre o aumento da sintese e liberacao dos compostos fenolicos e alteracao da parede celular dos vegetais, com o aumento das atividades de diversas enzimas, capazes de degradar a parede celular da planta e do microrganismo invasor, liberando fragmentos que podem atuar como moleculas sinalizadoras, tornando as plantas mais resistentes. Nesse trabalho as celulas de Rubus fruticosus (amora-preta) foram tratadas, separadamente, com tres diferentes moleculas elicitoras, ou seja, moleculas capazes de ativar o mecanismo de defesa das plantas, o acido salicilico (AS), o metil jasmonato (MeJA) e ramnoglucuronogalactana (F-I), na concentracao de 1 Êmol/L durante 1h, para o estudo dos componentes extracelulares liberados e das modificacoes dos monossacarideos da parede celular durante resposta de hipersensibilidade. A concentracao de proteinas totais extracelulares foi aumentada com os indutores F-I e MeJA. A atividade enzimatica de -D-xilosidase nao se alterou na presenca de F-I, AS e MeJA. Entretanto, o MeJA tem a capacidade de aumentar as atividades das enzimas -D-galactosidase, -Dglucosidase, quitinase e laminarinase e inibir as atividades das enzimas galacturonase e -Lfucosidase na concentracao e tempo usado. O AS e F-I provocaram um aumento nas atividades de galacturonase e quitinase e inibiram a laminarinase. A aplicacao exogena de F-I e AS induziram a liberacao de compostos fenolicos para meio extracelular, que provavelmente, foi decorrente da tentativa das celulas de se protegerem de microrganismos invasores, com um decrescimo desses compostos no meio intracelular. O MeJA nao foi capaz de alterar a sintese de compostos fenolicos totais intracelulares e extracelulares e de acucares extracelulares, em tais condicoes. Tambem F-I e AS nao alteraram o teor de acucar redutor extracelular. O MeJA foi mais efetivo na producao de ERO durante 30 minutos de incubacao na concentracao de1 Êmol/L . F-I foi tambem ativador na liberacao de ERO, no entanto, o AS provocou inibicao. Os principais monossacarideos neutros que constitui a parede celular de suspensao de celulas de Rubus fruticosus sao as glucose (55-61%), arabinose (22-29%) e manose (13,8-15%). Ocorrendo em menor concentracoes os monossacarideos de fucose (0,65-1,2%), galactose (0,5-0,8%), xilose (0,5-0,8%) e ramnose (aproximadamente 0,5%).Os monossacarideos ramnose, fucose, xilose e galactose de parede celular tiveram um decrescimo na presenca do AS e um aumento na presenca de MeJA. Entretanto, o AS e o MeJA nao alteraram o percentual de arabinose, manose e glucose. O F-I foi capaz de aumentar o percentual dos monossacarideos ramnose e fucose e diminuir de glucose. Os resultados obtidos demonstram que a via de ativacao dos mecanismos de defesa da celula vegetal, induzida pelo MeJA, difere das vias ativadas pelo AS e F-I, pois o F-I e o AS induziram a liberacao de compostos fenolicos e o MeJA provocou aumento nas atividades enzimaticas, principalmente que atuam na parede celular da propria planta. O AS e o F-I foram mais efetivos no aumento das atividades enzimaticsa relacionadas a defesa da planta, as quais agem nas paredes de diversos fitopatogenos, sendo que as enzimas que podem atuar na parede celular da propria planta foram inibidas ou nao sofreram alteracao. / The plant-pathogen interactions trigger a series of signals that are not yet completely understood. One of the mechanisms is the hypersensitive response (HR), which is characterized by cell death in the infection site in order to prevent pathogen proliferation. Our previous studies with different elicitors demonstrated the correlation between the formation of reactive oxygen species (ROS) and cell wall degradation. Here, the cells were elicited with 1 mol/L salicylic acid (SA), methyl jasmonate (MeJA) or acid polysaccharide (rhamnoglucuronogalactan, F-I) (1mol/L) from characterization the extracellular components released and the modifications of the monosaccharide composition in cell wall during a hypersensitive response in Rubus fruticosus (blackberry-black).The extracellular proteins released to the extracellular were increased with the inducers molecules F-I and MeJA. The -D-xylosidase enzymatic activities didnt change in the presence of F-I, SA and MeJA. The time-course curves for -D-galactosidase, -D-glucosidase activities in fraction E were most effective for MeJA, while F-I and AS inhibited -Dgalactosidase. Also, the MeJA has ability to activate laminarinase and chitinase enzymatic activities and inhibit galacturonase and -L-fucosidase enzymatic activities. After 1h, the SA and F-I caused an increase galacturonase and chitinase activities and inhibited laminarinase enzymatic activity. Also, the time-course curves chitinase in the fraction increased with SA.The F-I and SA increased extracellular phenolic compounds, although they decreased them in the fraction I. MeJA was unable to change the synthesis of either intracellular or extracellular phenolic compounds. The data suggest that F-I and AS modulate the defense responses of plants through a via different that of MeJA. The extracellular reducing sugar didnt change with F-I, SA and MeJA.The MeJA was more effective in the release ROS incubation of 30 minutes at concentration of 1 mol/L. However, the presence of SA caused inhibition and F-I activated of ROS by cells.The main constituents of neutral sugars in the cell wall of Rubus fruticosus were glucose (55-61%), arabinose (22-29%) and mannose (13.8-15%). Minor constituents were fucose (0.65-1.2%), galactose (0.5- 0.8%), xylose (0.5-0.8%) and rhamnose (~0.5%). SA decreased the rhamnose and fucose concentrations; F-I both decreased the percentage of mannose and glucose and increased rhamnose and fucose. MeJA, in turn, increased the percentage of rhamnose, xylose and galactose. The data suggest that F-I and SA modulate the defense responses of plants through a mechanism unrelated to the MeJA via. Since the F-I and the SA induced the release phenolic compounds and the MeJA increased in enzymatic activities, mainly age in the own plant cell wall. The SA and F-I were more effective in the increasing defense enzyme-related activity of the plant that acts on the walls of several phytopathogens, and the enzymes that can act in the cell wall of the plant were inhibited or did not change.

The purpose of this research was to investigate the effects that aspirin (ASA) and its metabolites, salicylic acid (SA) and acetic acid (AA), have on the delivery of drugs across biological barriers when used in conjunction with electroporation. Electroporation is a technique used to enhance drug delivery across bio-membranes in which a transmembrane potential is induced into cellular membranes, resulting in the creation of aqueous pores that allow molecules to pass through the otherwise impermeable barrier. Aspirin is a widely used drug that has been used for over a century and has been proven relatively safe at normal doses as indicated by the low number of reports of poisoning cases it has been involved in. Components of aspirin are known to soften the cellular membranes by solubilizing the cell's surface proteins. B16F10 murine melanoma cancer cells were used in this investigation and treated with a 120µM buffered solution of calcein, a fluorescent indicator, in which the amount of delivered tracer molecules was measured using fluorescence. Identical concentrations of ASA and SA were investigated (1mM, 5mM, and 10mM) separately, focusing the effects concentration has electroporation delivery. Diluted acetic acid was also investigated at pH values of 6.42, 5.36, and 4.40. The concentration of acetic acid that had the lowest pH and ASA with the highest concentration had the greatest impacts on the augmentation of calcein delivery. Therefore, this demonstrates that aspirin and acetic acid have the potential to improve targeted molecular delivery in combination with electroporation.

Emulsions are widely used as topical formulations in the pharmaceutical and cosmetic industry. They are thermodynamically unstable and require emulsifiers to stabilize them physically. A literature survey has revealed that emulsifiers could have an effect on topical delivery. Therefore, the overall aim of this research project was to investigate and to understand the various effects of biopolymers, chosen for this study as emulsifiers, on the release and the topical delivery of an active ingredient from emulsion-based delivery systems. Emulsions were stabilized by either whey protein alone or in combination with chitosan or carrageenan. Salicylic acid was chosen as a model drug. Furthermore, the emulsions were prepared at three different pH values (pH 4, 5 and 6) in order to introduce different charges to the polymeric emulsifiers and subsequently determine the effect of pH on release as well as on dermal and transdermal delivery. Emulsion characteristics, such as droplet size, zeta potential, viscosity and stability against creaming and coalescence were ascertained. In addition, turbidity was determined to evaluate the degree of insoluble complex formation in the aqueous phase of the emulsions. A high pressure liquid chromatographic (HPLC) method was validated for the quantitative determination of salicylic acid in the release, skin and transdermal perfusate samples. Nine emulsions were formulated, utilizing the layer-by-layer (LbL) self-assembly technique, from which the release of salicylic acid was determined. These release studies were conducted, utilizing nitrocellulose membranes (0.2 μm pore size) with the use of Franz-type diffusion cells in four replicates per formulation over a time period of 8 hours. Based on the emulsion characterization and release data, six formulations, including the oil solution, were chosen to determine dermal and transdermal delivery of salicylic acid. During the diffusion studies, the effect of different pH (whey protein pH 4.00, 5.00 and 6.00), different polymers and different polymer combinations were investigated. These diffusion studies were conducted with the use of dermatomed (thickness ~400 μm), human abdominal skin and Franz-type diffusion cells over a period of 24 hours. The characterization of the emulsions revealed no significant differences in the droplet size and viscosity between the various formulations. All emulsions showed stability towards coalescence over a time period of 7 days; however, not all the emulsions showed stability towards creaming and flocculation. The results of the release studies indicated that an increase in emulsion droplet charge could have a negative effect on the release of salicylic acid from these formulations. In contrast, positively charged emulsion droplets could enhance the dermal and transdermal delivery of salicylic acid from emulsions. It was hypothesized that electrostatic complex formation between the emulsifier and salicylic acid could affect the release, whereas electrostatic interaction between emulsion droplets and skin could influence dermal/transdermal delivery of the active. Furthermore, the degree of ionization of salicylic acid played an important role in the dermal and transdermal delivery of salicylic acid from the various emulsions. / MSc (Pharmaceutics), North-West University, Potchefstroom Campus, 2014

Emulsions are widely used as topical formulations in the pharmaceutical and cosmetic industry. They are thermodynamically unstable and require emulsifiers to stabilize them physically. A literature survey has revealed that emulsifiers could have an effect on topical delivery. Therefore, the overall aim of this research project was to investigate and to understand the various effects of biopolymers, chosen for this study as emulsifiers, on the release and the topical delivery of an active ingredient from emulsion-based delivery systems. Emulsions were stabilized by either whey protein alone or in combination with chitosan or carrageenan. Salicylic acid was chosen as a model drug. Furthermore, the emulsions were prepared at three different pH values (pH 4, 5 and 6) in order to introduce different charges to the polymeric emulsifiers and subsequently determine the effect of pH on release as well as on dermal and transdermal delivery. Emulsion characteristics, such as droplet size, zeta potential, viscosity and stability against creaming and coalescence were ascertained. In addition, turbidity was determined to evaluate the degree of insoluble complex formation in the aqueous phase of the emulsions. A high pressure liquid chromatographic (HPLC) method was validated for the quantitative determination of salicylic acid in the release, skin and transdermal perfusate samples. Nine emulsions were formulated, utilizing the layer-by-layer (LbL) self-assembly technique, from which the release of salicylic acid was determined. These release studies were conducted, utilizing nitrocellulose membranes (0.2 μm pore size) with the use of Franz-type diffusion cells in four replicates per formulation over a time period of 8 hours. Based on the emulsion characterization and release data, six formulations, including the oil solution, were chosen to determine dermal and transdermal delivery of salicylic acid. During the diffusion studies, the effect of different pH (whey protein pH 4.00, 5.00 and 6.00), different polymers and different polymer combinations were investigated. These diffusion studies were conducted with the use of dermatomed (thickness ~400 μm), human abdominal skin and Franz-type diffusion cells over a period of 24 hours. The characterization of the emulsions revealed no significant differences in the droplet size and viscosity between the various formulations. All emulsions showed stability towards coalescence over a time period of 7 days; however, not all the emulsions showed stability towards creaming and flocculation. The results of the release studies indicated that an increase in emulsion droplet charge could have a negative effect on the release of salicylic acid from these formulations. In contrast, positively charged emulsion droplets could enhance the dermal and transdermal delivery of salicylic acid from emulsions. It was hypothesized that electrostatic complex formation between the emulsifier and salicylic acid could affect the release, whereas electrostatic interaction between emulsion droplets and skin could influence dermal/transdermal delivery of the active. Furthermore, the degree of ionization of salicylic acid played an important role in the dermal and transdermal delivery of salicylic acid from the various emulsions. / MSc (Pharmaceutics), North-West University, Potchefstroom Campus, 2014

The aim of this study was to gain insight into the nature of resistance genes and mechanisms of resistance present in different ascochyta blight (AB) resistant genotypes of lentil to efficiently select non-allelic AB resistance genes mediating different mechanisms of resistance for gene pyramiding. Recombinant inbred lines (RILs) from all possible crosses among AB resistant Lens culinaris genotypes CDC Robin, 964a-46, ILL 7537 and ILL 1704 were subjected to allelism tests. Efforts were also made to understand the genetics of resistance in the L. ervoides accession L-01-827A. LR-18, a RIL population from the cross CDC Robin × 964a-46 was subjected to quantitative trait loci (QTL) mapping using a comprehensive genetic linkage map previously developed from polymorphic SNPs, SSRs and phenotypic markers. Results of allelism tests suggested that genes conditioning resistance to ascochyta blight in all lentil genotypes were non-allelic. Two complementary recessive resistance genes in L-01-827A were detected. QTL analysis indicated that CDC Robin and 964a-46 were different at two AB resistance QTLs. Histological tests suggested that cell death inhibition in CDC Robin, and reduced colonization of epidermal cells in 964a-46 might be the mechanisms of resistance in these genotypes. Comparing the expression of key genes in the salicylic acid (SA) and jasmonic acid (JA) signaling pathways of CDC Robin and 964a-46 suggested that the SA pathway was strongly triggered in 964a-46. However, the JA pathway was triggered in both, but at a lower expression level in 964a-46 than in CDC Robin. RNA-seq analysis revealed a number of candidate defense genes differentially expressed among genotypes with hypothetical actions in different layers of the plant defense machinery. The expression levels of the six candidate defense genes measured by quantitative real-time PCR analysis was correlated with those of RNA-seq. In conclusion, 964a-46 and CDC Robin mediated resistance to ascochyta blight through different resistant mechanisms, making them ideal candidates for resistance gene pyramiding. Gene pyramiding can be accelerated using closely linked markers to CDC Robin and 964a-46 resistance genes identified through QTL analysis.

Soybean [Glycine max (L.) Merr.] is an important crop worldwide. It has been widely consumed for protein, oil and other soy products. To develop soybean cultivars with greater resistance against pests and improved meal quality, it is important to elucidate the molecular bases of these traits. This dissertation aims to investigate the biochemical and biological functions of soybean genes from four gene families, which are hypothesized to be associated with soybean defense against pests and soybean meal quality. There are three specific objectives in this dissertation. The first one is to determine the function of components in the salicylic acid (SA) signaling pathway in soybean resistance against soybean cyst nematode (Heterodera glycines, SCN). The second one is to determine whether insect herbivory induce the emission of volatiles from soybean, and if so, how these volatiles are biosynthesized. The third objective is to identify and characterize soybean mannanase genes that can be used for the improvement of soybean meal quality. The soybean genome has been fully sequenced, which provides opportunities for cross-species comparison of gene families of interest and identification of candidate genes in soybean. The cloned cDNAs of putative genes were expressed in Escherichia coli to produce recombinant enzymes. Through biochemical assays, these proteins were proved to be soybean salicylic acid methyltransferase (GmSAMT1), methyl salicylate esterase (GmSABP2-1), α[alpha]-farnesene synthase (GmTPS1) and E-β[beta]-caryophyllene synthase (GmTPS2), and endo-β[beta]-mannanase (GmMAN1). Through a transgenic hairy root system harboring overexpression of GmSAMT1 and GmSABP2-1, both of these two genes were evaluated for their biological function related to resistance against SCN. The results showed that the over-expression of GmSAMT1 and GmSABP2-1 in the susceptible soybean background lead to enhanced resistance against SCN. Among four putative soybean mannanase genes, one gene was cloned and characterized. GmMAN1 showed the endo-β[beta]-mannanase hydrolyse activity and can hydrolyze cell walls isolated from soybean seeds. In summary, using comparative and functional genomics, a number of genes involved in soybean defense and meal quality were isolated and characterized. This study provides novel knowledge and molecular tools for the genetic improvement of soybean for enhanced resistance and improved meal quality.