Oxylipin formation in Nostoc punctiforme (PCC73102)

The dioxygenation of polyunsaturated fatty acids is mainly catalyzed by members of the lipoxygenase enzyme family in flowering plants and mosses. Lipoxygenase products can be metabolized further and are known as signalling substances that play a role in plant development as well as in plant responses to wounding and pathogen attack. Apart from accumulating data in mammals, flowering and non-flowering plants, information on the relevance of lipid peroxide metabolism in prokaryotic organisms is scarce. Thus we aimed to isolate and analyze lipoxygenases and oxylipin patterns from cyanobacterial origin. DNA isolated from Nostoc punctiforme strain PCC73102 yielded sequences for at least two different lipoxygenases. These have been cloned as cDNAs and named NpLOX1 and NpLOX2. Both proteins were identified as linoleate 13-lipoxygenases by expression in E. coli. NpLOX1 was characterized in more detail: It showed a broad pH optimum ranging from pH 4.5 to pH 8.5 with a maximum at pH 8.0 and alpha-linolenic acid was the preferred substrate. Bacterial extracts contain more 13-lipoxygenase-derived hydroperoxides in wounded than in non-wounded cells with a 30-fold excess of non-esterified over esterified oxylipins. 9-Lipoxygenase-derived derivatives were not detectable. 13-Lipoxygenase-derived hydroperoxides in esterified lipids were present at almost equal amounts compared to non-esterified hydroperoxides in non-wounded cells. These results suggest that 13-lipoxygenases acting on free fatty acids dominate in N. punctiforme strain PCC73102 upon wounding.     

Physical and ant-mediated refuges from parasitism: Implications for non-target effects in biological control

A promising natural enemy for release against the Asian soybean aphid, Aphis glycines Matsumura, in North America is the aphidiine braconid wasp Binodoxys communis (Gahan). The aphid Aphis monardae Oestlund, a native of North America’s tall-grass prairies, is a non-target species that may be at risk from releases of B. communis. This paper describes ecological facets of A. monardae populations in their native habitat that could protect them from attack by this exotic biological control agent. In prairie habitats, A. monardae populations aggregate in flower heads of their host plant, Monarda fistulosa L. On this host plant, aphids are also commonly tended by four ant species, and ant-tended colonies are larger than un-attended colonies. Laboratory studies showed that parasitism rates of A. monardae by B. communis are significantly higher on vegetative M. fistulosa than on M. fistulosa flower heads. In addition, attendance of A. monardae by the ant Lasius neoniger Emery significantly decreased parasitism by B. communis. Ants attacked and killed host-seeking adult parasitoids, and preyed upon B. communis mummies. No evidence was found that B. communis reared from A. monardae are less susceptible to attack by ants than parasitoids reared from A. glycines. M. fistulosa flower heads and attendance by L. neoniger may act as refuges for A. monardae against B. communis. Our work describes spatial refuges as ecological filters that separate non-target organisms from exotic natural enemies. Implications for classical biological control of A. glycines are discussed.     

Cloning and Drought Resistance Analysis of Soybean <i>GmHsps_p23-like</i> Gene

Soybean (Glycine max (L.) Merr.) is an important cultivated crop, which requires much water during its growth, and drought seriously affects soybean yields. Studies have shown that the expression of small heat shock proteins can enhance drought resistance, cold resistance and salt resistance of plants. In this experiment, soybean GmHsps_p23-like gene was successfully cloned by RT-PCR, the protein encoded by the GmHsps_p23-like gene was subjected to bioinformatics analysis, and the pCAMBIA3301-GmHsps_p23-like overexpression vector and pCBSG015-GmHsps_p23-like gene editing vector were constructed. Agrobacterium-mediated method was used to transform soybeans to obtain positive plants. RT-PCR detection, rehydration experiment and drought resistance physiological and biochemical index detection were performed on the T₂ generation positive transgenic soybean plants identified by PCR and Southern hybridization. The results showed that the overexpression vector plant GmHsps_p23-like gene expression increased. After rehydration, the transgenic overexpression plants returned to normal growth, and the damage to the plants was low. After drought stress, the SOD and POD activities and the PRO content of the transgenic overexpression plants increased, while the MDA content decreased. The reverse was true for soybean plants with genetically modified editing vectors. The drought resistance of the overexpressed soybeans under drought stress was higher than that of the control group, and had a stronger drought resistance. It showed that the expression of soybean GmHsps_p23-like gene can improve the drought resistance of soybean. The cloning and functional verification of soybean GmHsps_p23-like gene had not been reported yet. This is the first time that PCR technology has been used to amplify the soybean GmHsps_p23-like gene and construct an expression vector for this gene. This research has laid the foundation for transgenic technology to improve plant drought resistance and cultivate new drought-resistant transgenic soybean varieties.     

Genetic variants in root architecture-related genes in a Glycine soja accession,a potential resource to improve cultivated soybean

Background

Root system architecture is important for water acquisition and nutrient acquisition for all crops. In soybean breeding programs, wild soybean alleles have been used successfully to enhance yield and seed composition traits, but have never been investigated to improve root system architecture. Therefore, in this study, high-density single-feature polymorphic markers and simple sequence repeats were used to map quantitative trait loci (QTLs) governing root system architecture in an inter-specific soybean mapping population developed from a cross between Glycine max and Glycine soja.

Results

Wild and cultivated soybean both contributed alleles towards significant additive large effect QTLs on chromosome 6 and 7 for a longer total root length and root distribution, respectively. Epistatic effect QTLs were also identified for taproot length, average diameter, and root distribution. These root traits will influence the water and nutrient uptake in soybean. Two cell division-related genes (D type cyclin and auxin efflux carrier protein) with insertion/deletion variations might contribute to the shorter root phenotypes observed in G. soja compared with cultivated soybean. Based on the location of the QTLs and sequence information from a second G. soja accession, three genes (slow anion channel associated 1 like, Auxin responsive NEDD8-activating complex and peroxidase), each with a non-synonymous single nucleotide polymorphism mutation were identified, which may also contribute to changes in root architecture in the cultivated soybean. In addition, Apoptosis inhibitor 5-like on chromosome 7 and slow anion channel associated 1-like on chromosome 15 had epistatic interactions for taproot length QTLs in soybean.

Conclusion

Rare alleles from a G. soja accession are expected to enhance our understanding of the genetic components involved in root architecture traits, and could be combined to improve root system and drought adaptation in soybean.

Electronic supplementary material

The online version of this article (doi:10.1186/s12864-015-1334-6) contains supplementary material, which is available to authorized users.     

Genome-wide association study for flowering time,maturity dates and plant height in early maturing soybean (Glycine max) germplasm

Background

Soybean (Glycine max) is a photoperiod-sensitive and self-pollinated species. Days to flowering (DTF) and maturity (DTM), duration of flowering-to-maturity (DFTM) and plant height (PH) are crucial for soybean adaptability and yield. To dissect the genetic architecture of these agronomically important traits, a population consisting of 309 early maturity soybean germplasm accessions was genotyped with the Illumina Infinium SoySNP50K BeadChip and phenotyped in multiple environments. A genome-wide association study (GWAS) was conducted using a mixed linear model that involves both relative kinship and population structure.

Results

The linkage disequilibrium (LD) decayed slowly in soybean, and a substantial difference in LD pattern was observed between euchromatic and heterochromatic regions. A total of 27, 6, 18 and 27 loci for DTF, DTM, DFTM and PH were detected via GWAS, respectively. The Dt1 gene was identified in the locus strongly associated with both DTM and PH. Ten candidate genes homologous to Arabidopsis flowering genes were identified near the peak single nucleotide polymorphisms (SNPs) associated with DTF. Four of them encode MADS-domain containing proteins. Additionally, a pectin lyase-like gene was also identified in a major-effect locus for PH where LD decayed rapidly.

Conclusions

This study identified multiple new loci and refined chromosomal regions of known loci associated with DTF, DTM, DFTM and/or PH in soybean. It demonstrates that GWAS is powerful in dissecting complex traits and identifying candidate genes although LD decayed slowly in soybean. The loci and trait-associated SNPs identified in this study can be used for soybean genetic improvement, especially the major-effect loci associated with PH could be used to improve soybean yield potential. The candidate genes may serve as promising targets for studies of molecular mechanisms underlying the related traits in soybean.

Electronic supplementary material

The online version of this article (doi:10.1186/s12864-015-1441-4) contains supplementary material, which is available to authorized users.     

SNP identification and marker assay development for high-throughput selection of soybean cyst nematode resistance

Background

Soybean cyst nematode (SCN) is the most economically devastating pathogen of soybean. Two resistance loci, Rhg1 and Rhg4 primarily contribute resistance to SCN race 3 in soybean. Peking and PI 88788 are the two major sources of SCN resistance with Peking requiring both Rhg1 and Rhg4 alleles and PI 88788 only the Rhg1 allele. Although simple sequence repeat (SSR) markers have been reported for both loci, they are linked markers and limited to be applied in breeding programs due to accuracy, throughput and cost of detection methods. The objectives of this study were to develop robust functional marker assays for high-throughput selection of SCN resistance and to differentiate the sources of resistance.

Results

Based on the genomic DNA sequences of 27 soybean lines with known SCN phenotypes, we have developed Kompetitive Allele Specific PCR (KASP) assays for two Single nucleotide polymorphisms (SNPs) from Glyma08g11490 for the selection of the Rhg4 resistance allele. Moreover, the genomic DNA of Glyma18g02590 at the Rhg1 locus from 11 soybean lines and cDNA of Forrest, Essex, Williams 82 and PI 88788 were fully sequenced. Pairwise sequence alignment revealed seven SNPs/insertion/deletions (InDels), five in the 6th exon and two in the last exon. Using the same 27 soybean lines, we identified one SNP that can be used to select the Rhg1 resistance allele and another SNP that can be employed to differentiate Peking and PI 88788-type resistance. These SNP markers have been validated and a strong correlation was observed between the SNP genotypes and reactions to SCN race 3 using a panel of 153 soybean lines, as well as a bi-parental population, F₅–derived recombinant inbred lines (RILs) from G00-3213 x LG04-6000.

Conclusions

Three functional SNP markers (two for Rhg1 locus and one for Rhg4 locus) were identified that could provide genotype information for the selection of SCN resistance and differentiate Peking from PI 88788 source for most germplasm lines. The robust KASP SNP marker assays were developed. In most contexts, use of one or two of these markers is sufficient for high-throughput marker-assisted selection of plants that will exhibit SCN resistance.

Electronic supplementary material

The online version of this article (doi:10.1186/s12864-015-1531-3) contains supplementary material, which is available to authorized users.     

Thermo-mechanical extrusion pretreatment for conversion of soybean hulls to fermentable sugars

Thermo-mechanical extrusion pretreatment for lignocellulosic biomass was investigated using soybean hulls as the substrate. The enzyme cocktail used to hydrolyze pretreated soybean hulls to fermentable sugars was optimized using response surface methodology (RSM). Structural changes in substrate and sugar yields from thermo-mechanical processing were compared with two traditional pretreatment methods that utilized dilute acid (1% sulfuric acid) and alkali (1% sodium hydroxide). Extrusion processing parameters (barrel temperature, in-barrel moisture, screw speed) and processing aids (starch, ethylene glycol) were studied with respect to reducing sugar and glucose yields. The conditions resulting in the highest cellulose to glucose conversion (95%) were screw speed 350 rpm, maximum barrel temperature 80 °C and in-barrel moisture content 40% wb. Compared with untreated soybean hulls, glucose yield from enzymatic hydrolysis of soybean hulls increased by 69.6%, 128.7% and 132.2%, respectively, when pretreated with dilute acid, alkali and extrusion.     

Cannabidiol as an emergent therapeutic strategy for lessening the impact of inflammation on oxidative stress

Oxidative stress with reactive oxygen species generation is a key weapon in the arsenal of the immune system for fighting invading pathogens and initiating tissue repair. If excessive or unresolved, however, immune-related oxidative stress can initiate further increasing levels of oxidative stress that cause organ damage and dysfunction. Targeting oxidative stress in various diseases therapeutically has proven more problematic than first anticipated given the complexities and perversity of both the underlying disease and the immune response. However, growing evidence suggests that the endocannabinoid system, which includes the CB₁ and CB₂ G-protein-coupled receptors and their endogenous lipid ligands, may be an area that is ripe for therapeutic exploitation. In this context, the related nonpsychotropic cannabinoid cannabidiol, which may interact with the endocannabinoid system but has actions that are distinct, offers promise as a prototype for anti-inflammatory drug development. This review discusses recent studies suggesting that cannabidiol may have utility in treating a number of human diseases and disorders now known to involve activation of the immune system and associated oxidative stress, as a contributor to their etiology and progression. These include rheumatoid arthritis, types 1 and 2 diabetes, atherosclerosis, Alzheimer disease, hypertension, the metabolic syndrome, ischemia-reperfusion injury, depression, and neuropathic pain.