Soybean Tissues Research Articles

Functional Characterisation of a Calmodulin-Binding Receptor-Like Cytoplasmic Kinase (GmCBRLCK1) in Glycine max (L.) Merr. using Bioinformatic Tools

An understanding of the function of signaling genes/proteins in soybean is vital for comprehending plant growth and development. The objective of this study was to functionally characterize a calmodulin-binding receptor-like cytoplasmic kinase gene (Glyma.13G161700) from Glycine max. Bioinformatic analyses were performed for the characterization. Expression profile of GmCBRLCK1 gene in soybean tissue was assessed using Genevisible. Functional genomic analysis for gene expression regulation and co-expression analysis was evaluated using micro array data from Affymetrix Soybean Genome Array platform in GENEVESTIGATOR v3. Gene ontology functional predictions were determined through FFPred 2.0. The results showed that the calmodulin-binding receptor-like cytoplasmic kinase gene is predominantly expressed in the pericycle and syncytium in root seedlings and in the palisade cells of the legume. The gene was shown to be highly upregulated in response to root exposure to Phytophthora sojae, Heterodera glycines and aluminium stress. Co-expressed genes during the legume development showed Pearson’s correlation co-efficient of 1 to Glyma.13G161700. Gene ontology predictions confirmed the signaling and metabolic functions of the kinase gene and its primary locations are the membrane and endomembrane system of G. max. The study therefore suggests that Glycine max calmodulin-binding receptor-like cytoplasmic kinase (GmCBRLCK1) is involved in receptor signaling pathways to enhance seedling tolerance to root infection by P. sojae, H. glycines, and to aluminium stress. The kinase gene is also involved in regulation of metabolic processes that aid in growth and development of soybean seedling.

Overexpression of soybean miR169c confers increased drought stress sensitivity in transgenic Arabidopsis thaliana

The miR169 family, a large-scale microRNA gene family conserved in plants, is involved in stress responses, although how soybean miR169 functions in response to drought stress remains unclear. We show that gma-miR169c exerts a negative regulatory role in the response to drought stress by inhibiting the expression of its target gene, nuclear factor Y–A (NF-YA). A real-time RT-PCR analysis indicated that gma-miR169c is widely expressed in soybean tissues and induced by polyethylene glycol (PEG), high salt, cold stress and abscisic acid (ABA). Histochemical ß-glucuronidase (GUS) staining showed that the gma-miR169c promoter drives GUS reporter gene expression in various transgenic Arabidopsis tissues, and the stress-induced pattern was confirmed in transgenic Arabidopsis and transgenic soybean hairy roots. Arabidopsis overexpressing gma-miR169c is more sensitive to drought stress, with reduced survival, accelerated leaf water loss, and shorter root length than wild-type plants. We identified a precise cleavage site for 10 gma-miR169c targets and found reduced transcript levels of the AtNFYA1 and AtNFYA5 transcription factors in gma-miR169c-overexpressing Arabidopsis and reduced expression of the stress response genes AtRD29A, AtRD22, AtGSTU25 and AtCOR15A. These results indicate that gma-miR169c plays a negative regulatory role in drought stress and is a candidate miRNA for improving plant drought adaptation.

Sodium nitroprusside enhances regeneration and alleviates salinity stress in soybean [Glycine max (L.) Merrill

Abstract SNP (Sodium nitroprusside) a Nitric oxide (NO) donor, plays varied roles in the growth and development of plants. Hence, in the present study, we have demonstrated that SNP enhances regeneration in half-seed explants of soybean cv. PUSA 9712, when cultured in Shoot Induction Medium (SIM) containing 4.44 μM BA and 30 μM SNP. About (91.0) % of explants formed shoots in the presence of SNP, compared to (76.33) % as observed on SIM with 4.44 μM BA alone. Supplementation of 30 μM SNP in rooting medium (RM) containing 4.93 μM IBA, produced the highest number of rooted plantlets. The plants regenerated in the presence of SNP displayed improved characteristics (mean shoot length = 9.21 cm, mean root length = 14.19 cm) as compared to plants regenerated in control medium devoid of SNP. Salinity stress studies revealed that, application of 50 μM SNP, reduces browning, drying of soybean tissues and increased the plant survivability, further analysis revealed that supplementation of SNP results in stabilization of Na+ and K+ ion ratio, activates SOD, CAT enzyme expression and reduce the concentrations of MDA and H2O2, thereby reversing the effects of salinity stress. These results signify that SNP enhances regeneration and development rate of soybean plants, and application of SNP alleviates salinity stress manifested by NaCl.

Effects of phosphorus amended low phosphorus soil on soybean (Glycine max L.) and wheat (Titicum aestivum L.) yield and phosphorus uptake

A major constraint for crop production on disturbed soils is phosphorus (P). A 2-year field study was conducted on a disturbed soil to evaluate broiler litter ash (BLA) as an inexpensive phosphorus fertilizer for soybean. BLA or super phosphate (SP) was applied at four rates and planted with soybean followed by wheat. At soybean growth stage R3, two plants from each plot were removed for tissue analysis. Soybean tissue P concentration distributions were in the order pods > leaves > stems > roots. At maturity, soybean grain and wheat tissue yields were not significantly affected by P source. Except for the high superphosphate rate for the second crop, P concentrations of soybean grain and wheat tissue were not significant between P source. In this study, BLA was as effective as SP for growth of soybean grain and wheat tissue, suggesting that BLA can be used as an inexpensive P fertilizer on low P disturbed soils.

SECONDARY PLANT RESOURCES AS PROSPECTIVE UNCONVENTIONAL SOURCES OF PECTIС SUBSTANCES

The secondary raw materials have been studied as sources of pectic substances necessary for the endo-ecological protection of the organism in the globally deteriorating living conditions of modern humans. The article reveals the significance and long-term benefits of such sources of pectic substances as fruit and seed coats, which are obtained in considerable quantities as a secondary raw material during the implementation of the technological process, and often do not find rational use. Research has been carried out on new prospective sources of pectin substances – secondary resources of processing soybean Glycine max (L.) Merrill, sainfoin Onobrýchis arenária, rapeseed Brassica napus L. oleifera, Sarepta mustard Brassica juncea (L.) Czern, and black mustard Brassica nigra (L.) W.D.J. Koch, castor bean Ricinus communis L., sunflower Helianthus annuus L. Fruit and seed coats of these plant species have been studied. The prospects of their secondary resources for pectin production have been shown. The assessment of the quantitative and qualitative characteristics of the pectic substances of the objects under study, as well as their fractional composition and analytical indicators, make it possible to characterize the potential functional, technological and therapeutic properties of pectin preparations. It has been indicated that in the polyuronid component (fraction of galacturonic acid), all the studied samples of surface tissues of soybean, mustard, sainfoin, sunflower, one rape variety meet international requirements for food pectin (52.87–73.22%), and one of them, the pectin from seed coat of the Valenta variety, meets the requirements for pectins for medical purposes (75.83%). Pectic substances of soybean, mustard, castor bean varieties are characterized by a high degree of esterification (62.37–76.88%) in contrast to the varieties of sainfoin and sunflower (45.29–55.15%). According to the degree of esterification, rape varieties are close to low-esterified pectiс substances – 59.34–61.48%. The prospects of using seed and fruit membranes as an unconventional secondary plant raw material to improve the environmental performance of production and to obtain a valuable therapeutic-and-prophylactic food ingredient have been substantiated.

Residues of thiamethoxam and mefenoxam in vegetative and floral tissue of soybean at the early reproductive stage resulting from seed treatments

Thiamethoxam with mefenoxam is the most widely used neonicotinoid insecticide/fungicide mixture applied to soybean (Glycine max [L]) as seed treatments. Based on the systemic nature of thiamethoxam and mefenoxam, residues of this insecticide/fungicide mixture may be present in soybean vegetative and floral tissue and negatively impact beneficial insects. Although neonicotinoids are often applied in combination with systemic fungicides, the research on ecological risks of neonicotinoids has been focused on the analysis of these compounds without considering their interaction with other agrochemicals. The objective of this study was to identify the concentration of thiamethoxam and mefenoxam in soybean flowers and leaves during early reproductive soybean stages. A field experiment with three treatments: a thiamethoxam-mefenoxam combination, thiamethoxam only, and untreated seeds, was conducted. Flowers were collected during early reproductive soybean stages R1-R2 at different locations in Nebraska during two years. Quantification of the pesticides in floral tissue was conducted using a modification of the QuEChErs extraction method and HPLC-MS/MS analysis. Mean concentrations of thiamethoxam and mefenoxam in floral and vegetative tissue were exteremely low or not detected although trace levels of thiamethoxam were higher in floral tissues from seed treatments relative to the control. The only residue consistently detected above the method detection limit among plants grown from thiamethoxam treated seeds was the thiamethoxiam metabolite, clothianidin. Results from this study provide important baseline information to estimate the window of activity for this compound in soybean in the North Central Region of the United States.

Transgene-product expression levels in genetically engineered breeding stacks are equivalent to those of the single events

ABSTRACTTransgene product expression levels are measured in genetically engineered (GE) crops containing single transformation events and the measured expression levels are then utilized in food, feed, and environmental safety assessments as part of the requirements for de-regulation of the event. Many countries also require measurement of expression levels and safety assessments for GE breeding stacks, even though the breeding stacks are composed of single events that have been previously assessed. Transgene product expression levels were measured in tissues of maize, soybean, and cotton breeding stacks and each of their component single events. Expression levels in the breeding stacks were plotted against expression levels in the single events to quantify the ability of the single events to predict transgene product expression levels in the breeding stacks. These results indicate that transgene product expression levels in single events are a reliable indicator of expression levels in breeding stacks. Based on these results it is concluded that safety assessments for breeding stacks can be conducted using transgene product expression levels from single events.

Genome Editing in Soybean with CRISPR/Cas9.

CRISPR/Cas9 mediated genome editing technology has experienced rapid advances in recent years and has been applied to a wide variety of plant species, including soybean. Several platforms have been developed for designing and cloning of single CRISPR targets or multiple targets in a single destination vector. This chapter provides an updated working protocol for applying CRISPR/Cas9 technology to target a single gene or multiple genes simultaneously in soybean. We describe two platforms for cloning single CRISPR targets and multiplexing targets, respectively, and reagent delivery methodologies. The protocols address crucial limiting steps that can limit CRISPR editing in soybean hairy roots, composite plants, and tissue culture-based regenerated whole plants. To date, transgenic soybean plants with mutagenesis in up to three target genes have been obtained with this procedure.

Genome-wide Identification and Bioinformatics Analysis of Soybean CHX Gene Family

Cation proton exchanger (CHX) gene family belongs to CPA2 (cation proton antiporter 2) super family and its N-terminal has a Na + /H + exchanger domain, which regulates various biological processes mainly by transporting cation and proton in plants. In this study, a total of 40 soybean CHX genes from whole genome sequence were screened by using bioinformatics. Chromosome localization analysis showed that soybean CHX genes were distributed on 19 different chromosomes. Further syntenic analysis revealed that most genes were from gene duplication. Phylogenetic analysis exhibited that 40 soybean CHX genes could be divided into 5 subfamilies. Gene structure and conserved motif analysis demonstrated that CHX genes from different subfamilies were conserved in terms of gene structure and conserved motif. Soybean tissue expression data analysis uncovered that CHX genes were mainly expressed in flowers.

GmLEA2-1, a Late Embryogenesis Abundant Protein Gene Isolated from Soybean (Glycine max (L.) Merr.), Confers Tolerance to Abiotic Stress

Late embryonic proteins (LEA) gene family was abundant mainly in higher plant embryos, which could protect the embryos from the damage caused by abiotic stress, especially drought and salt stresses. In the present study, GmLEA2-1 was cloned from soybean leaf tissue treated by 10% polyethylene glycol 6000 (PEG6000). The results of quantitative real-time PCR (qRT-PCR) revealed a variety of expression patterns of GmLEA2-1 in various tissues of soybean (root, stem, leaf, flower, pod, early embryo and late embryo). GmLEA2-1 gene shared a lower sequence similarity with other typical LEA genes of same group from different species, but similar functions. Overexpression of GmLEA2-1 in transgenic Arabidopsis thaliana conferred tolerance to drought and salt stresses. The fresh weight and dry weight of seedling, the primary root length and the lateral root density of transgenic Arabidopsis plants were higher than those of wild type Arabidopsis (WT) under drought and salt stresses. Cis-acting regulatory elements in the GmLEA2-1 promoter were also predicted. These data demonstrate that GmLEA2-1 protein play an important role in improving drought and salt tolerance in plants.

Variability of CP4 EPSPS expression in genetically engineered soybean (Glycine max L. Merrill)

The expression of the CP4 EPSPS protein in genetically engineered (GE) soybean confers tolerance to the Roundup® family of agricultural herbicides. This study evaluated the variability of CP4 EPSPS expression using an enzyme-linked immunosorbent assay in soybean tissues collected across diverse germplasm and 74 different environments in Argentina, Brazil and the USA. Evaluated material included single and combined (stacked) trait products with other GE traits in entries with cp4 epsps gene at one or two loci. The highest level of CP4 EPSPS was observed in leaf tissues, intermediate in forage and seed, and lowest in root tissues. Varieties with two loci had approximately twice the level of CP4 EPSPS expression compared to one locus entries. Variable and non-directional level of CP4 EPSPS was observed with other factors like genetic background, trait stacking, growing region or season. The maximum and average CP4 EPSPS expression levels in seed provided large margins of exposure (MOE of approximately 4000 and 11,000, respectively), mitigating concerns over exposure to this protein in food and feed from soybean varieties tolerant to Roundup® herbicides.

Different glyceollin synthesis-related metabolic content and gene expressions in soybean callus suspension cultures and cotyledon tissues induced by alginate oligosaccharides

Abstract Glyceollins are a group of inducible soybean phytoalexins. The aim of the present study was to investigate the mechanism of glyceollin production in callus suspension cultures (CS) and cotyledon tissues elicited with alginate oligosaccharides (AOS) at 1%, 2%, and 3% concentrations that were applied for three days. HPLC analysis of the extracts from 2% AOS-elicited callus suspension cultures (ECS) revealed that glyceollins content was 85.3-fold and 8.2-fold higher than that in unelicited controls and elicited cotyledon tissues (ECT), respectively. UPLC-Q-Exactive Orbitrap MS analysis showed that the 2% AOS induction resulted in elevated levels of metabolites, the intermediary products of glyceollin biosynthesis, such as daidzein, glycitein, genistein, naringenin, glycinol, glyceollidin I/II, and glyceollin I, II, and III in ECS and ECT. Glyceollin I was prominent among the three glyceollin isomers in ECS, whereas isomer II and III were dominant in the synthetic route for glyceollins in ECT. qRT-PCR analysis of related genes showed that UGT, CYP93A1, G2DT, and G4DT displayed a direct effect on glyceollin synthesis. Our results suggested that 2% AOS-induced CS produced glyceollins in higher content compared to ECT by altering metabolite content and gene expression. Elicitation of CS is thus a promising technology for glyceollin synthesis extensively.

Genome-wide analysis of genes encoding core components of the ubiquitin system in soybean (Glycine max) reveals a potential role for ubiquitination in host immunity against soybean cyst nematode

BackgroundUbiquitination is a major post-translational protein modification that regulates essentially all cellular and physiological pathways in eukaryotes. The ubiquitination process typically involves three distinct classes of enzymes, ubiquitin-activating enzyme (E1), ubiquitin-conjugating enzyme (E2) and ubiquitin ligase (E3). To date, a comprehensive identification and analysis of core components comprising of the whole soybean (Glycine max) ubiquitin system (UBS) has not been reported.ResultsWe performed a systematic, genome-wide analysis of genes that encode core members of the soybean UBS in this study. A total of 1431 genes were identified with high confidence to encode putative soybean UBS components, including 4 genes encoding E1s, 71 genes that encode the E2s, and 1356 genes encoding the E3-related components. Among the E3-encoding genes, 760 encode RING-type E3s, 124 encode U-box domain-containing E3s, and 472 encode F-box proteins. To find out whether the identified soybean UBS genes encode active enzymes, a set of genes were randomly selected and the enzymatic activities of their recombinant proteins were tested. Thioester assays indicated proteins encoded by the soybean E1 gene GmUBA1 and the majority of selected E2 genes are active E1 or E2 enzymes, respectively. Meanwhile, most of the purified RING and U-box domain-containing proteins displayed E3 activity in the in vitro ubiquitination assay. In addition, 1034 of the identified soybean UBS genes were found to express in at least one of 14 soybean tissues examined and the transcript level of 338 soybean USB genes were significantly changed after abiotic or biotic (Fusarium oxysporum and Rhizobium strains) stress treatment. Finally, the expression level of a large number of the identified soybean UBS-related genes was found significantly altered after soybean cyst nematode (SCN) treatment, suggesting the soybean UBS potentially plays an important role in soybean immunity against SCN.ConclusionsOur findings indicate the presence of a large and diverse number of core UBS proteins in the soybean genome, which suggests that target-specific modification by ubiquitin is a complex and important part of cellular and physiological regulation in soybean. We also revealed certain members of the soybean UBS may be involved in immunity against soybean cyst nematode (SCN). This study sets up an essential foundation for further functional characterization of the soybean UBS in various physiological processes, such as host immunity against SCN.

Effects of Potassium Fertilizer Rates on Soybean Looper (Lepidoptera: Noctuidae) Development.

Potassium (K) has an important impact on physiological and biochemical processes in plants. Soybean, Glycine max (L.) Merrill, requires high K availability for optimal yield. However, changes in nutrient availability in plants may also affect herbivore population size and/or development. Soybean looper, Chrysodeixis includens (Walker) (Lepidoptera: Noctuidae), is one of the most destructive pests of soybean in the southern United States. In this study, we evaluated the effects of different K fertilization rates on soybean looper development, soybean seed weight, and soybean seed nutritional quality. Soybean plants were supplied with six different rates of K fertilizer (0, 33.6, 67.3, 100.9, 134.5, and 168.1 kg/ha as K2O). Soybean leaves were sampled at R1, R3, R5, and R6 stages and fed to soybean looper in laboratory bioassays. Soybean looper mortality, fecundity, and fertility were not significantly affected by feeding on leaf tissues of soybean treated with different potassium fertilizer rates. However, soybean looper consumed more leaf tissue and spent less time completing larval development when fed on foliage from treatments of 134.5 and 168.1 kg/ha. Pupal weight significantly increased at 134.5 and 168.1 kg/ha. There was no significant difference in percentage of protein, oil, and fiber in soybean seeds among six K fertilizer rates. Percentage of K in soybean seeds and 100 seed weight were significantly enhanced at 168.1 kg/ha. Nitrogen (N) content of foliage was not affected by applying K fertilizer at different rates. Our results indicate that higher K fertilizer rates can enhance soybean seed weight but also facilitate soybean looper development.

Relationships between compound lipophilicity on seed coat permeability and embryo uptake by soybean and corn

AbstractSystemic uptake of organic compounds from roots to leaves follows a Gaussian distribution in relation to the lipophilicity, as measured by the logKow. Quantification of compound uptake with different lipophilicities, and applied as a seed treatment that diffuses through the seed coat into the embryo during imbibition, has not been reported. The aim of this investigation was to quantify the uptake of non-ionic compounds into seeds of soybean and corn. A series of fluorescent piperonyl amides were synthesized and a novel combinatorial pharmacodynamic technique was developed that provided a range of compounds from logKow0.02 to 5.7. Seeds were treated with a mixture of amides, imbibed and compounds chemically extracted and quantified by high-performance liquid chromatography using a fluorescence detector. The maximum uptake efficiency of the applied amide mixture from whole soybean and corn seeds was 67% at logKow2.9, and 43% at logKow3.4, respectively. The critical partition coefficient for uptake for both species was <4.2 logKow. Seeds were dissected and separated as soybean embryo and testa, and corn internal tissues (embryo + endosperm) or seed covering layers (pericarp + testa), and >75% of the amides were found in the soybean embryo or corn internal tissues compared with the covering layers at logKow<4.2. The distribution of amides showed that the corn seed covering layer had similar hydrophilic/lipophilic properties as internal tissues, while soybean tissues had different hydrophilic/lipophilic properties. Collectively, the Gaussian uptake pattern for systemic uptake into plants was not found for either seed species.

Quantitative 3D imaging of cell level auxin and cytokinin response ratios in soybean roots and nodules.

Legume-Rhizobium symbiosis results in root nodules where rhizobia fix atmospheric nitrogen into plant usable forms in exchange for plant-derived carbohydrates. The development of these specialized root organs involves a set of carefully orchestrated plant hormone signalling. In particular, a spatio-temporal balance between auxin and cytokinin appears to be crucial for proper nodule development. We put together a construct that carried nuclear localized fluorescence sensors for auxin and cytokinin and used two photon induced fluorescence microscopy for concurrent quantitative 3-dimensional imaging to determine cellular level auxin and cytokinin outputs and ratios in root and nodule tissues of soybean. The use of nuclear localization signals on the markers and nuclei segmentation during image processing enabled accurate monitoring of outputs in 3D image volumes. The ratiometric method used here largely compensates for variations in individual outputs due to sample turbidity and scattering, an inherent issue when imaging thick root and nodule samples typical of many legumes. Overlays of determined auxin/cytokinin ratios on specific root zones and cell types accurately reflected those predicted based on previously reported outputs for each hormone individually. Importantly, distinct auxin/cytokinin ratios corresponded to distinct nodule cell types indicating a key role for these hormones in nodule cell type identity.

Antioxidant genes of plants and fungal pathogens are distinctly regulated during disease development in different Rhizoctonia solani pathosystems.

Biotic stress, as a result of plant-pathogen interactions, induces the accumulation of reactive oxygen species in the cells, causing severe oxidative damage to plants and pathogens. To overcome this damage, both the host and pathogen have developed antioxidant systems to quench excess ROS and keep ROS production and scavenging systems under control. Data on ROS-scavenging systems in the necrotrophic plant pathogen Rhizoctonia solani are just emerging. We formerly identified vitamin B6 biosynthetic machinery of R. solani AG3 as a powerful antioxidant exhibiting a high ability to quench ROS, similar to CATALASE (CAT) and GLUTATHIONE S-TRANSFERASE (GST). Here, we provide evidence on the involvement of R. solani vitamin B6 biosynthetic pathway genes; RsolPDX1 (KF620111.1), RsolPDX2 (KF620112.1), and RsolPLR (KJ395592.1) in vitamin B6 de novo biosynthesis by yeast complementation assays. Since gene expression studies focusing on oxidative stress responses of both the plant and the pathogen following R. solani infection are very limited, this study is the first coexpression analysis of genes encoding vitamin B6, CAT and GST in plant and fungal tissues of three pathosystems during interaction of different AG groups of R. solani with their respective hosts. The findings indicate that distinct expression patterns of fungal and host antioxidant genes were correlated in necrotic tissues and their surrounding areas in each of the three R. solani pathosystems: potato sprout-R. solani AG3; soybean hypocotyl-R. solani AG4 and soybean leaves-R. solani AG1-IA interactions. Levels of ROS increased in all types of potato and soybean tissues, and in fungal hyphae following infection of R. solani AGs as determined by non-fluorescence and fluorescence methods using H2DCF-DA and DAB, respectively. Overall, we demonstrate that the co-expression and accumulation of certain plant and pathogen ROS-antioxidant related genes in each pathosystem are highlighted and might be critical during disease development from the plant’s point of view, and in pathogenicity and developing of infection structures from the fungal point of view.

Auxin-to-Gibberellin Ratio as a Signal for Light Intensity and Quality in Regulating Soybean Growth and Matter Partitioning.

The intensity and quality (red to far-red (R/Fr) ratio) of light directly affect growth of plant under shading. Gibberellins (GAs) and auxin [indole-3-acetic acid (IAA)] play important roles in mediating the shading adaptive responses of plants. Thus, the intensity and quality of the uncoupling light from shading were assessed to identify the influence of each component on the morphology and matter distribution of the leaf, stem, and petiole. This assessment was based on the changes in endogenous Gibberellin 1 (GA1) and IAA levels. Soybean plants were grown in a growth chamber with four treatments [normal (N), N+Fr, low (L), and L+Fr light]. Results revealed that the reductions in photosynthetically active radiation (PAR) and R/Fr ratio equally increased height and stem mass fractions (SMFs) of the soybean seedling. The light intensity significantly influenced the dry mass per unit area and mass fraction of soybean leaves, whereas the light quality regulated the petiole elongation and mass fraction. Low R/Fr ratio (high Fr light) increased the soybean biomass by improving the photosynthetic assimilation rate and quantum yield of photosystem II. In addition, the IAA and GA1 levels in the leaf, stem, and petiole did not reflect the growth response trends of each tissue toward light intensity and quality; however, trends of the IAA-to-GA1 content ratios were similar to those of the growth and matter allocation of each soybean tissue under different light environments. Therefore, the response of growth and matter allocation of soybean to light intensity and quality may be regulated by the IAA-to-GA1 content ratio in the tissues of the soybean plant.

Carbon Isotope Ratio Fractionation among Plant Tissues of Soybean

Carbon isotope ratio (δ13C) has been used as a proxy for water use efficiency (WUE) in several crops. We compared δ13C of soybean [Glycine max (L.) Merr.] tissues sampled at bloom with δ13C of mature seed (MS). Twenty Maturity Group IV accessions with contrasting δ13C values were evaluated in three environments. Genotype and environment effects on δ13C were significant for the uppermost mature trifoliolate leaf, center leaflets from main stems, whole shoot, and MS, but there were no significant genotype by environment interactions, indicating that genotype rankings were similar among environments. Repeatability of δ13C among tissues ranged from 0.79 to 0.94, and MS δ13C values were significantly correlated with δ13C from other tissues (r ≥ 0.69). For genotypes of similar maturity, MS δ13C may be used as a selection tool for WUE, simplifying the use of δ13C for high‐throughput phenotyping.

Characterization of Soybean WRKY Gene Family and Identification of Soybean WRKY Genes that Promote Resistance to Soybean Cyst Nematode

WRKY proteins are a superfamily of plant transcription factors with important roles in plants. WRKY proteins have been extensively analyzed in plant species including Arabidopsis and rice. Here we report characterization of soybean WRKY gene family and their functional analysis in resistance to soybean cyst nematode (SCN), the most important soybean pathogen. Through search of the soybean genome, we identified 174 genes encoding WRKY proteins that can be classified into seven groups as established in other plants. WRKY variants including a WRKY-related protein unique to legumes have also been identified. Expression analysis reveals both diverse expression patterns in different soybean tissues and preferential expression of specific WRKY groups in certain tissues. Furthermore, a large number of soybean WRKY genes were responsive to salicylic acid. To identify soybean WRKY genes that promote soybean resistance to SCN, we first screened soybean WRKY genes for enhancing SCN resistance when over-expressed in transgenic soybean hairy roots. To confirm the results, we transformed five WRKY genes into a SCN-susceptible soybean cultivar and generated transgenic soybean lines. Transgenic soybean lines overexpressing three WRKY transgenes displayed increased resistance to SCN. Thus, WRKY genes could be explored to develop new soybean cultivars with enhanced resistance to SCN.