Sortilin acts as an endocytic receptor for α-synuclein fibril.

Cell-to-cell spreading of misfolded α-synuclein (αSYN) is supposed to play a key role in the pathological progression of Parkinson's disease (PD) and other synucleinopathies. Receptor-mediated endocytosis has been shown to contributes to the uptake of αSYN in both neuronal and glial cells. To determine the receptor involved in αSYN endocytosis on the cell surface, we performed unbiased, and comprehensive screening using a membrane protein library of the mouse whole brain combined with affinity chromatography and mass spectrometry. The candidate molecules hit in the initial screening were validated by co-immunoprecipitation using cultured cells; sortilin, a vacuolar protein sorting 10 protein family sorting receptor, exhibited the strongest binding to αSYN fibrils. Notably, the intracellular uptake of fibrillar αSYN was slightly but significantly altered, depending on the expression level of sortilin on the cell surface, and time-lapse image analyses revealed the concomitant internalization and endosomal sorting of αSYN fibrils and sortilin. Domain deletion in the extracellular portion of sortilin revealed that the ten conserved cysteines (10CC) segment of sortilin was involved in the binding and endocytosis of fibrillar αSYN; importantly, pretreatment with a 10CC domain-specific antibody significantly hindered αSYN fibril uptake. The presence of sortilin in the core structure of Lewy bodies and glial cytoplasmic inclusions in the brain of synucleinopathy patients was confirmed via immunohistochemistry, and the expression level of sortilin in mesencephalic dopaminergic neurons may be altered with disease progression. These results provide compelling evidence that sortilin acts as an endocytic receptor for pathogenic form of αSYN, and yields important insight for the development of disease-modifying targets for synucleinopathies.

A Case of Corticobasal Syndrome and Posterior Cortical Atrophy With Biomarkers of Alzheimer Disease.

Corticobasal syndrome is a clinical entity characterized by asymmetric akinetic rigidity and a variety of higher cortical dysfunction. Predicting background pathology of corticobasal syndrome is rather challenging; however, clinical and neuroimaging findings may provide a clue to its etiopathological origin. Visuospatial dysfunction of posterior cortical atrophy and logopenic-type language impairment indicate the presence of Alzheimer's disease-related pathology, and they provide useful information in distinguishing Alzheimer's disease from other types of corticobasal syndrome. Here we describe a case of corticobasal syndrome who showed characteristic visuospatial symptoms with imaging evidence of Alzheimer's disease supported by amyloid-PET and tau/astrogliosis-PET. Early, accurate diagnosis based on clinical features and predictable biomarkers is mandatory to the success of early intervention in corticobasal syndrome associated with Alzheimer's disease.

Parkinson's disease-linked DNAJC13 mutation aggravates alpha-synuclein-induced neurotoxicity through perturbation of endosomal trafficking.

Mutations in DNAJC13 gene have been linked to familial form of Parkinson's disease (PD) with Lewy pathology. DNAJC13 is an endosome-related protein and believed to regulate endosomal membrane trafficking. However, the mechanistic link between DNAJC13 mutation and α-synuclein (αSYN) pathology toward neurodegeneration remains poorly understood. In this study, we showed that PD-linked N855S-mutant DNAJC13 caused αSYN accumulation in the endosomal compartment, presumably due to defective cargo trafficking from the early endosome to the late and/or recycling endosome. In vivo experiments using human αSYN transgenic flies showed that mutant DNAJC13 not only increased the amount of insoluble αSYN in fly head but also induced dopaminergic neurodegeneration, rough eye phenotype and age-dependent locomotor impairment. Together, these findings suggest that DNAJC13 mutation perturbs multi-directional endosomal trafficking, resulting in the aberrant endosomal retention of αSYN, which might predispose to the neurodegenerative process that leads to PD.

Clinical and Cerebral Metabolic Changes in Parkinson's Disease With Basal Forebrain Atrophy.

BACKGROUND: Cholinergic dysfunction plays a key role in cognitive dysfunction in Parkinson's disease (PD). Recent studies revealed that atrophy in the nucleus basalis of Meynert (NBM), the largest cholinergic nucleus in the basal forebrain, heralds cognitive decline in PD. Despite clinical importance of NBM atrophy in PD, clinical and radiological correlates of NBM atrophy remains to be elucidated. OBJECTIVE: We investigated the longitudinal changes in clinical and cerebral glucose metabolic characteristics in PD with atrophy in the NBM. METHODS: We analyzed the 3-year longitudinal data of 56 PD patients who underwent motor, nonmotor, and imaging evaluations at baseline. The patients were classified into PD with and without NBM atrophy based on the results of magnetic resonance imaging volumetry. We compared clinical characteristics and cerebral glucose metabolic changes between PD with and without NBM atrophy. RESULTS: At baseline, 20 patients and 36 patients were classified into PD with and without NBM atrophy groups, respectively. At follow-up, the data of the 14 PD patients in the NBM atrophy group and the 18 patients in the group without NBM atrophy completed full assessments and were available for the analysis. The PD with NBM atrophy group showed severe cognitive dysfunction and psychiatric symptoms both at baseline and follow-up. The NBM volume significantly correlated with motor and nonmotor functions. The PD with NBM atrophy showed significantly reduced metabolism in the parietal and occipital cortices both at baseline and follow-up. CONCLUSIONS: Basal forebrain atrophy is a simple and sensible marker of faster disease progression and cortical hypometabolism in PD. © 2020 International Parkinson and Movement Disorder Society.

Identification of a cytochrome P450 hydroxylase, CYP81E22, as a causative gene for the high sensitivity of soybean to herbicide bentazon.

KEY MESSAGE: A frame shift invoked by a single-base deletion in the gene encoding a cytochrome P450 hydroxylase, CYP81E22, causes the loss of bentazon detoxification function in soybean. Bentazon is an effective herbicide in soybean cultivation applied at post-emergence stages for control of several broadleaf weeds. However, some soybean cultivars are highly sensitive to bentazon and are killed upon application. In this study, the gene related to the high sensitivity of soybean cultivars to bentazon was mapped to chromosome 16, and its location was narrowed down to a 257-kb region where three cytochrome P450 genes were located. In these genes, a single-base deletion of cytosine was detected in the coding region of Glyma.16G149300, CYP81E22, at + 1465 bp downstream from the translation start codon, leading to a frame shift in the open reading frame and creating a premature stop codon. This stop codon resulted in the loss of more than half of the P450, and consequently, the remaining molecule failed to form a functioning protein. This single-base deletion was common among the highly sensitive cultivars screened from the soybean mini-core collection and other previously reported highly sensitive cultivars. Furthermore, we screened plant lines from the targeting-induced local lesions in genomes library of the soybean cultivar Enrei based on a modelled 3D structure of CYP81E22. The lines with mutations in Glyma.16G149300 were highly sensitive to bentazon, which provides strong evidence that Glyma.16G149300 is the gene responsible for high sensitivity to bentazon.

Extracellular α-synuclein enters dopaminergic cells by modulating flotillin-1-assisted dopamine transporter endocytosis.

The neuropathological hallmarks of Parkinson's disease (PD) include the appearance of α-synuclein (α-SYN)-positive Lewy bodies (LBs) and the loss of catecholaminergic neurons. Thus, a potential mechanism promoting the uptake of extracellular α-SYN may exist in susceptible neurons. Of the various differentially expressed proteins, we are interested in flotillin (FLOT)-1 because this protein is highly expressed in the brainstem catecholaminergic neurons and is strikingly up-regulated in PD brains. In this study, we found that extracellular monomeric and fibrillar α-SYN can potentiate FLOT1-dopamine transporter (DAT) binding and pre-endocytic clustering of DAT on the cell surface, thereby facilitating DAT endocytosis and down-regulating its transporter activity. Moreover, we demonstrated that α-SYN itself exploited the DAT endocytic process to enter dopaminergic neuron-like cells, and both FLOT1 and DAT were found to be the components of LBs. Altogether, these findings revealed a novel role of extracellular α-SYN on cellular trafficking of DAT and may provide a rationale for the cell type-specific, functional, and pathologic alterations in PD.-Kobayashi, J., Hasegawa, T., Sugeno, N., Yoshida, S., Akiyama, T., Fujimori, K., Hatakeyama, H., Miki, Y., Tomiyama, A., Kawata, Y., Fukuda, M., Kawahata, I., Yamakuni, T., Ezura, M., Kikuchi, A., Baba, T., Takeda, A., Kanzaki, M., Wakabayashi, K., Okano, H., Aoki, M. Extracellular α-synuclein enters dopaminergic cells by modulating flotillin-1-assisted dopamine transporter endocytosis.

DNA marker-assisted evaluation of cooked bean hardness of three soybean progeny lines.

Cooked bean hardness is an important trait for the processing of soybean products such as nimame, natto, miso, and soy sauce. Previously, we showed that cooked bean hardness is primarily affected by the pectin methylesterase gene Glyma03g03360, and that calcium content has a secondary effect on this trait. To establish a simple and timely method for the evaluation of cooked bean hardness, primers of amplification refractory mutation system-polymerase chain reaction (ARMS-PCR) were designed to detect a single-nucleotide polymorphism of Glyma03g03360 and subsequently used to evaluate three soybean progeny lines. The determined genotypes were compared to those identified using the cleaved amplified polymorphic sequence (CAPS) method. Seven out of 284 lines presented different genotypes, which were determined using the two methods: A genotypes were incorrectly assigned as heterozygous by CAPS, suggesting that ARMS-PCR is more reliable. Glyma03g03360 genotypes could be used to evaluate cooked bean hardness, except for intermediate values. Cooked bean hardness within the same genotype groups was significantly correlated with calcium contents. These findings indicate that ARMS-PCR is useful for a marker-assisted selection of soybean with soft-cooked beans and that calcium content may be used for additional selection.

Mapping versatile QTL for soybean downy mildew resistance.

KEY MESSAGE: Three versatile QTL for soybean downy mildew resistance in Japan were detected using five RIL populations and confirmed using recombinant fixed pairs or a backcrossed line. Downy mildew reduces soybean seed quality and size. It is a problem in Japan, where 90% of soybean grown is used as food. In the USA, 33 downy mildew races have been reported, but race differentiation in Japan is unclear. To identify quantitative trait loci (QTL) for downy mildew resistance effective in the Kanto and Tohoku regions, we performed QTL analysis using five populations of recombinant inbred lines (RILs) originated from 'Natto-shoryu' × 'Tachinagaha' (NT), 'Natto-shoryu' × 'Suzumaru', 'Satonohohoemi' × 'Fukuibuki' (SF), 'Kinusayaka' × 'COL/Akita/2009/TARC/1,' and 'YR-82' × 'Harosoy' over a 4-year period (2014-2017). We evaluated spontaneously developed symptoms of the RILs and applied 112-233 polymorphic markers to each population. Out of 31 QTL detected, we found five on chromosome 3 in three populations and another five on chromosome 7 in three populations. Other QTL were detected in one population, nine of them in different years. In the NT population, two QTL were detected in a 3.0-Mb region on chromosome 7 and in an 8.1-Mb region on chromosome 18 by evaluating nine recombinant fixed pairs in both Kanto and Tohoku regions. In the SF population, a QTL on chromosome 8 was detected in both regions. This QTL was introduced into the 'Satonohohoemi' background by backcrossing, and its effect was confirmed in both regions. In summary, two QTL on chromosomes 7 and 18 from the NT population and one QTL on chromosome 8 from the SF population were confirmed to be effective in both Tohoku and Kanto regions.

Isolation and characterization of induced mutants in the gene associated with seed cadmium accumulation in soybean.

Food contamination by cadmium (Cd) is a serious threat to human health. Thus, it is imperative to prevent Cd accumulation in staple crops like soybean. The development of low Cd accumulating cultivars is an effective solution. To this end, it is essential to identify the gene(s) controlling seed Cd accumulation. Although Glyma.09G055600 (GmHMA3) seems to be associated with Cd accumulation in soybean, it has not been established if it is responsible for seed Cd accumulation. In the present study, the effect of GmHMA3 on seed Cd accumulation in soybean was validated using three independent GmHMA3 mutants isolated from an ethyl methanesulfonate-induced soybean mutant library. Each of mutant had an amino acid substitution in GmHMA3 and segregating progenies were developed by crossing the original cultivar with each of the three mutants. The relationship between these three mutations and seed Cd accumulation was investigated. While two of them significantly increased seed Cd accumulation corresponding to previous reports of a natural missense mutation in GmHMA3, the other slightly decreased seed Cd accumulation. Overall, these results indicate that GmHMA3 is responsible for seed Cd accumulation in soybean.

Effect of change from a determinate to a semi-determinate growth habit on the yield and lodging resistance of soybeans in the northeast region of Japan.

Although an indeterminate growth habit is attractive to develop high-yield soybean varieties with higher number of pods (Glycine max (L). Merr.), lodging in indeterminate varieties remains a problem in Japan. As the semi-determinate varieties have shorter main stem length than the indeterminate varieties, this trait can be useful to improve varieties with high yield and low lodging risk. We introduced the genes Dt1 and Dt2, which regulate stem growth habit, into three determinate varieties by backcrossing and evaluated the resulting effects on yield and lodging tendency under four different growing environments. The yield and lodging degree of the semi-determinate and indeterminate lines were higher and more severe than those of the determinate lines. Despite the lower overall lodging score, the semi-determinate lines had marginally lower overall yield than that of the indeterminate lines. However, the effect of introduction of semi-determinate traits on yield and lodging degree was different in the three backgrounds, with the yield of semi-determinate lines being the highest and the difference in lodging degree between the semi-determinate and determinate lines being under 1.0 in one background. Therefore, semi-determinate growth habit has potential to develop high yielding varieties with low lodging risk.

The effect of stem growth habit on single seed weight and seed uniformity in soybean (Glycine max (L.) Merrill).

The timing of flower formation and length of the seed-filling period of indeterminate growth soybean varieties vary more than those of determinate varieties (Glycine max (L.) Merrill). These variations have been hypothesized to affect single seed weight and its uniformity which determine the processing quality of soybean used in foods. We derived near isogenic lines (NILs) with different growth characteristics from an indeterminate line (donor parent) and three determinate lines with heavy seeds (recurrent parents), and evaluated the effects of growth habit on seed weight and its uniformity. Each NIL population consisting of five indeterminate and five determinate BC4F4 lines tested at two locations in two different years with two replications. Split-plot analysis of variance, with main-plot and sub-plot being cross combination and growth habit, respectively, showed that indeterminate varieties had slightly heavier seeds than determinate varieties and that there was no significant difference in uniformity of single seed weights. The effects of growth habit on seed uniformity was related to genetic background, but differences between the two growth characteristics were less than the differences among genetic background. This indicates that indeterminate growth habit did not much influence seed weight or its uniformity.

Membrane Trafficking Illuminates a Path to Parkinson's Disease.

Parkinson's disease (PD) is the second most common neurodegenerative disorder that is characterized by progressive movement disability and a variety of non-motor symptoms. The neuropathology of PD consists of the loss of dopaminergic neurons in the midbrain and the appearance of neuronal inclusions called Lewy bodies, which contain insoluble α-synuclein, a relatively small protein originally identified in association with synaptic vesicles in the presynaptic nerve terminals. Drugs that replenish dopamine can partly alleviate the motor symptoms, but they do not cure the disease itself. Therefore, there is an urgent need for disease modification in terms of the delay or prevention of neurodegeneration. Recent advances in genetic and biochemical studies have provided unifying conceptual frameworks of the pathogenesis of PD. Particularly, membrane trafficking has aroused special attention as an initiator or enhancer of the neurodegenerative process that leads to PD. Defects in the cellular trafficking pathway result in synaptic dysfunction and the accumulation of misfolded α-synuclein. Likewise, changes in intracellular sorting and degradation profoundly influence the cellular trafficking of misfolded proteins, thereby facilitating the cell-to-cell spreading of hazardous α-synuclein species in a prion-like manner. Here, we will review our current knowledge of the functional roles of membrane trafficking in PD and will discuss how this cellular process could induce or facilitate the functional and pathological alterations in this disease.

Transfer of the Rsv3 locus from 'Harosoy' for resistance to soybean mosaic virus strains C and D in Japan.

Resistance to soybean mosaic virus (SMV) is imperative for soybean (Glycine max (L.) Merr.) production in the Tohoku region. Molecular markers for SMV resistance were previously reported for U.S. SMV strains, but they cannot be applied because of the differences in strain classification between Japan and the U.S. A U.S. variety 'Harosoy' has been used mainly as a donor of resistance to SMV strains C and D in a Japanese breeding program, resulting in resistant varieties such as 'Fukuibuki.' Because 'Harosoy' harbors the Rsv3 gene conferring resistance to the virulent SMV strain groups, G5 through G7, it appears that the Rsv3 gene confers resistance to strains C and D. In this study, we introduced resistance to the two strains from 'Fukuibuki' into a leading variety 'Ohsuzu' by recurrent backcrossing with marker-assisted selection. All lines selected with markers near Rsv3 showed resistance to the strains, suggesting that the Rsv3 locus is responsible for the resistance. Three years of trials showed that one of the breeding lines, 'Tohoku 169,' was equivalent to 'Ohsuzu' with respect to agricultural characteristics such as seed size, maturity date, and seed yield, except for the SMV resistance.

Lys-63-linked ubiquitination by E3 ubiquitin ligase Nedd4-1 facilitates endosomal sequestration of internalized α-synuclein.

α-Synuclein (aS) is a major constituent of Lewy bodies, which are not only a pathological marker for Parkinson disease but also a trigger for neurodegeneration. Cumulative evidence suggests that aS spreads from cell to cell and thereby propagates neurodegeneration to neighboring cells. Recently, Nedd4-1 (neural precursor cell expressed developmentally down-regulated protein 4-1), an E3 ubiquitin ligase, was shown to catalyze the Lys-63-linked polyubiquitination of intracellular aS and thereby facilitate aS degradation by the endolysosomal pathway. Because Nedd4-1 exerts its activity in close proximity to the inner leaflet of the plasma membrane, we speculate that after the internalization of aS the membrane resident aS is preferentially ubiquitinated by Nedd4-1. To clarify the role of Nedd4-1 in aS internalization and endolysosomal sequestration, we generated aS mutants, including ΔPR1(1-119 and 129-140), ΔC(1-119), and ΔPR2(1-119 and 134-140), that lack the proline-rich sequence, a putative Nedd4-1 recognition site. We show that wild type aS, but not ΔPR1, ΔPR2, or ΔC aS, is modified by Nedd4-1 in vitro, acquiring a Lys-63-linked ubiquitin chain. Compared with the mutants lacking the proline-rich sequence, wild type-aS is preferentially internalized and translocated to endosomes. The overexpression of Nedd4-1 increased aS in endosomes, whereas RNAi-mediated silencing of Nedd4-1 decreased endosomal aS. Although aS freely passes through plasma membranes within minutes, a pulse-chase experiment revealed that the overexpression of Nedd4-1 markedly decreased the re-secretion of internalized aS. Together, these findings demonstrate that Nedd4-1-linked Lys-63 ubiquitination specifies the fate of extrinsic and de novo synthesized aS by facilitating their targeting to endosomes.

The Sg-1 glycosyltransferase locus regulates structural diversity of triterpenoid saponins of soybean.

Triterpene saponins are a diverse group of biologically functional products in plants. Saponins usually are glycosylated, which gives rise to a wide diversity of structures and functions. In the group A saponins of soybean (Glycine max), differences in the terminal sugar species located on the C-22 sugar chain of an aglycone core, soyasapogenol A, were observed to be under genetic control. Further genetic analyses and mapping revealed that the structural diversity of glycosylation was determined by multiple alleles of a single locus, Sg-1, and led to identification of a UDP-sugar-dependent glycosyltransferase gene (Glyma07g38460). Although their sequences are highly similar and both glycosylate the nonacetylated saponin A0-αg, the Sg-1(a) allele encodes the xylosyltransferase UGT73F4, whereas Sg-1(b) encodes the glucosyltransferase UGT73F2. Homology models and site-directed mutagenesis analyses showed that Ser-138 in Sg-1(a) and Gly-138 in Sg-1(b) proteins are crucial residues for their respective sugar donor specificities. Transgenic complementation tests followed by recombinant enzyme assays in vitro demonstrated that sg-1(0) is a loss-of-function allele of Sg-1. Considering that the terminal sugar species in the group A saponins are responsible for the strong bitterness and astringent aftertastes of soybean seeds, our findings herein provide useful tools to improve commercial properties of soybean products.

Seed yield and its components of indeterminate and determinate lines in recombinant inbred lines of soybean.

The present study was conducted to evaluate the benefits of indeterminate growth habit in breeding to improve yield potential of Japanese soybean varieties, which exclusively have determinate growth habit. Two populations of recombinant inbred lines (RILs) derived from crosses between determinate Japanese cultivars and indeterminate US cultivars were grown in Akita and Kyoto, and seed weight per plant (SW) and its components were compared between indeterminate and determinate RILs. The difference of SW between the two growth habits in RILs varied depending on maturation time. The SW of early indeterminate lines was significantly higher than that of early determinate ones in Akita, but not in Kyoto. Among yield components, the number of seeds per pod was constantly larger in indeterminate lines than that in determinate ones irrespective of maturation time. The number of seeds per plant and the number of pods per plant of the indeterminate lines were greater than those of the determinate lines in early maturation in Akita. These results suggest that the indeterminate growth habit is an advantageous characteristic in breeding for high yield of early maturing soybean varieties in the Tohoku region.

[Utility of a Simultaneous Detection Kit for Glutamate Dehydrogenase and Toxin A/B with Toxigenic Culture in the Diagnosis and Treatment of Clostridium difficile Infection].

We examined how doctors evaluate the results of C. DIFF QUIK CHEK COMPLETE (COMPLETE) in the diagnosis and treatment of Clostridium difficile infection (CDI). A total of 887 stool samples submitted from 2012 to 2013 were examined with COMPLETE. Requested specimens among samples with discrepant results were inoculated onto CCMA plates and incubated under anaerobic conditions for 48 h, then retested by COMPLETE if positive culture results were obtained. Of the 887 specimens, 198 (22.3%) were glutamate dehydrogenase-positive and 73(8.3%) were toxin-positive. Of the 125 specimens yielding discrepant results, 106 specimens were cultured and retested, with 46 (43.4%, 46/106) proving toxin-positive. As a result, the total number of toxin-positive results increased from 73 (8.3%, 73/887) to 119 (13.4%, 119/887). This change was significant (p<0.01). We analyzed the relationship between doctor's decision-making and timing of receiving CD test results in 81 specimens among the discrepant results. Twenty-four patients started treatment just after obtaining the first test result (29.6%, 24/81) and the toxin-positive ratio of the second test was 62.5% (15/24). The decision to start treatment was made after obtaining results of the second test in 48 patients, of whom 13 (16.0%, 13/81) started treatment, and the toxin-positive ratio was 37.5% (18/48). The difference in toxin ratio was significant (p < 0.05). The increase in toxin-positive ratio in the final report facilitates diagnosis in patients with CDL Many doctors, however, started treatment before obtaining results from the second test, suggesting that the 3-day delay in report results represents a drawback for this system.

VPS35 dysfunction impairs lysosomal degradation of α-synuclein and exacerbates neurotoxicity in a Drosophila model of Parkinson's disease.

Mutations in vacuolar protein sorting 35 (VPS35) have been linked to familial Parkinson's disease (PD). VPS35, a component of the retromer, mediates the retrograde transport of cargo from the endosome to the trans-Golgi network. Here we showed that retromer depletion increases the lysosomal turnover of the mannose 6-phosphate receptor, thereby affecting the trafficking of cathepsin D (CTSD), a lysosome protease involved in α-synuclein (αSYN) degradation. VPS35 knockdown perturbed the maturation step of CTSD in parallel with the accumulation of αSYN in the lysosomes. Furthermore, we found that the knockdown of Drosophila VPS35 not only induced the accumulation of the detergent-insoluble αSYN species in the brain but also exacerbated both locomotor impairments and mild compound eye disorganization and interommatidial bristle loss in flies expressing human αSYN. These findings indicate that the retromer may play a crucial role in αSYN degradation by modulating the maturation of CTSD and might thereby contribute to the pathogenesis of the disease.

A major and stable QTL associated with seed weight in soybean across multiple environments and genetic backgrounds.

KEY MESSAGE: We detected a QTL for single seed weight in soybean that was stable across multiple environments and genetic backgrounds with the use of two recombinant inbred line populations. Single seed weight (SSW) in soybean is a key determinant of both seed yield and the quality of soy food products, and it exhibits wide variation. SSW is under genetic control, but the molecular mechanisms of such control remain unclear. We have now investigated quantitative trait loci (QTLs) for SSW in soybean and have identified such a QTL that is stable across multiple environments and genetic backgrounds. Two populations of 225 and 250 recombinant inbred lines were developed from crosses between Japanese and US cultivars of soybean that differ in SSW by a factor of ~2, and these populations were grown in at least three different environments. A whole-genome panel comprising 304 simple sequence repeat (SSR) loci was applied to mapping in each population. We identified 15 significant QTLs for SSW dispersed among 11 chromosomes in the two populations. One QTL located between Sat_284 and Sat_292 on chromosome 17 was detected (3.6 < LOD < 14.1) in both populations grown in all environments. This QTL, tentatively designated qSw17-1, accounted for 9.4-20.9 % of phenotypic variation in SSW, with a dominant allele being associated with increased SSW. Given its substantial effect on SSW, qSw17-1 is an attractive target for positional cloning, and SSR markers closely associated with this locus may prove useful for marker-assisted selection for SSW control in soybean.

Genetic and chemical analysis of a key biosynthetic step for soyasapogenol A, an aglycone of group A saponins that influence soymilk flavor.

Although certain saponins in soybean seeds have been reported to have health benefits, group A acetyl saponins cause undesirable bitter and astringent tastes in soy products. Therefore, reduction or elimination of group A saponins is an important target for soybean breeders. A wide survey of cultivated and wild soybean germplasm identified a mutant line that lacked group A saponins. The absence of soyasapogenol A, a group A saponin aglycone, is controlled by a single recessive allele, sg-5 that mapped genetically near the SSR marker, Satt117, on soybean chromosome 15 (linkage group E). The locus is epistatic to Sg-1, which controls the terminal sugar variation on the C-22 sugar chain of soyasapogenol A, and allelic differences at this locus lead to changes in the amount of DDMP saponins and their derivatives group B and E products. These findings provide a new insight into the biosynthetic pathway of soybean saponins, and identify a genetic approach that can be applied to improve the quality of foods produced from soybean.