Genome-Wide Association Studies for Dynamic Plant Height and Number of Nodes on the Main Stem in Summer Sowing Soybeans

Plant height (PH) and the number of nodes on the main stem (NN) serve as major plant architecture traits affecting soybean seed yield. Although many quantitative trait loci for the two traits have been reported, their genetic controls at different developmental stages in soybeans remain unclear. Here, 368 soybean breeding lines were genotyped using 62,423 single nucleotide polymorphism (SNP) markers and phenotyped for the two traits at three different developmental stages over two locations in order to identify their quantitative trait nucleotides (QTNs) using compressed mixed linear model (CMLM) and multi-locus random-SNP-effect mixed linear model (mrMLM) approaches. As a result, 11 and 13 QTNs were found by CMLM to be associated with PH and NN, respectively. Among these QTNs, 8, 3, and 4 for PH and 6, 6, and 8 for NN were found at the three stages, and 3 and 6 were repeatedly detected for PH and NN. In addition, 34 and 30 QTNs were found by mrMLM to be associated with PH and NN, respectively. Among these QTNs, 11, 13, and 16 for PH and 11, 15, and 8 for NN were found at the three stages. A majority of these QTNs overlapped with the previously reported loci. Moreover, one QTN within the known E2 locus for flowering time was detected for the two traits at all three stages, and another that overlapped with the Dt1 locus for stem growth habit was also identified for the two traits at the mature stage. This may explain the highly significant correlation between the two traits. Our findings provide evidence for mixed major plus polygenes inheritance for dynamic traits and an extended understanding of their genetic architecture for molecular dissection and breeding utilization in soybeans

Methylglyoxal Mediates Adipocyte Proliferation by Increasing Phosphorylation of Akt1

Methylglyoxal (MG) is a highly reactive metabolite physiologically presented in all biological systems. The effects of MG on diabetes and hypertension have been long recognized. In the present study, we investigated the potential role of MG in obesity, one of the most important factors to cause metabolic syndrome. An increased MG accumulation was observed in the adipose tissue of obese Zucker rats. Cell proliferation assay showed that 5–20 µM of MG stimulated the proliferation of 3T3-L1 cells. Further study suggested that accumulated-MG stimulated the phosphorylation of Akt1 and its targets including p21 and p27. The activated Akt1 then increased the activity of CDK2 and accelerated the cell cycle progression of 3T3-L1 cells. The effects of MG were efficiently reversed by advanced glycation end product (AGE) breaker alagebrium and Akt inhibitor SH-6. In summary, our study revealed a previously unrecognized effect of MG in stimulating adipogenesis by up-regulation of Akt signaling pathway and this mechanism might offer a new approach to explain the development of obesity

Dual effects of fructose on ChREBP and FoxO1/3α are responsible for AldoB up-regulation and vascular remodelling

Abstract Increased production of methylglyoxal (MG) in vascular tissues is one of the causative factors for vascular remodelling in different subtypes of metabolic syndrome, including hypertension and insulin resistance. Fructose-induced up-regulation of aldolase B (AldoB) contributes to increased vascular MG production but the underlying mechanisms are unclear. Serum levels of MG and fructose were determined in diabetic patients with hypertension. MG level had significant positive correlations with blood pressure and fructose level respectively. C57BL/6 mice were fed with control or fructose-enriched diet for 3 months and ultrasonographic and histologic analyses were performed to evaluate arterial structural changes. Fructose-fed mice exhibited hypertension and high levels of serum MG with normal glucose level. Fructose intake increased blood vessel wall thickness and vascular smooth muscle cell (VSMC) proliferation. Western blotting and real-time PCR analysis revealed that AldoB level was significantly increased in both the aorta of fructose-fed mice and the fructose-treated VSMCs, whereas aldolase A (AldoA) expression was not changed. The knockdown of AldoB expression prevented fructose-induced MG overproduction and VSMC proliferation. Moreover, fructose significantly increased carbohydrate-responsive element-binding protein (ChREBP), phosphorylated FoxO1/3α and Akt1 levels. Fructose induced translocation of ChREBP from the cytosol to nucleus and activated AldoB gene expression, which was inhibited by the knockdown of ChREBP . Meanwhile, fructose caused FoxO1/3α shuttling from the nucleus to cytosol and inhibited its binding to AldoB promoter region. Fructose-induced AldoB up-regulation was suppressed by Akt1 inhibitor but enhanced by FoxO1/3α siRNA. Collectively, fructose activates ChREBP and inactivates FoxO1/3α pathways to up-regulate AldoB expression and MG production, leading to vascular remodelling

Identification of Major Quantitative Trait Loci for Seed Oil Content in Soybeans by Combining Linkage and Genome-Wide Association Mapping

Soybean oil is the most widely produced vegetable oil in the world and its content in soybean seed is an important quality trait in breeding programs. More than 100 quantitative trait loci (QTLs) for soybean oil content have been identified. However, most of them are genotype specific and/or environment sensitive. Here, we used both a linkage and association mapping methodology to dissect the genetic basis of seed oil content of Chinese soybean cultivars in various environments in the Jiang-Huai River Valley. One recombinant inbred line (RIL) population (NJMN-RIL), with 104 lines developed from a cross between M8108 and NN1138-2, was planted in five environments to investigate phenotypic data, and a new genetic map with 2,062 specific-locus amplified fragment markers was constructed to map oil content QTLs. A derived F2 population between MN-5 (a line of NJMN-RIL) and NN1138-2 was also developed to confirm one major QTL. A soybean breeding germplasm population (279 lines) was established to perform a genome-wide association study (GWAS) using 59,845 high-quality single nucleotide polymorphism markers. In the NJMN-RIL population, 8 QTLs were found that explained a range of phenotypic variance from 6.3 to 26.3% in certain planting environments. Among them, qOil-5-1, qOil-10-1, and qOil-14-1 were detected in different environments, and qOil-5-1 was further confirmed using the secondary F2 population. Three loci located on chromosomes 5 and 20 were detected in a 2-year long GWAS, and one locus that overlapped with qOil-5-1 was found repeatedly and treated as the same locus. qOil-5-1 was further localized to a linkage disequilibrium block region of approximately 440 kb. These results will not only increase our understanding of the genetic control of seed oil content in soybean, but will also be helpful in marker-assisted selection for breeding high seed oil content soybean and gene cloning to elucidate the mechanisms of seed oil content

MG induced adipogenesis in 3T3-L1 adipocytes.

<p>After treated with MG, SH-6 or alagebrium for 48 h, cells were cultured till confluence and differentiation. The Oil Red O staining in adipocytes was shown in (<b><i>A</i></b>). The lipid content in adipocytes from different groups was quantified and presented as the percentage of that from control cells (<b><i>B</i></b>). The mRNA expression of adiponectin, PPARγ, C/EBPα and leptin in differentiated cells treated with MG alone or with MG and alagebrium were determined by real-time PCR (<b><i>C</i></b>). *P<0.05; **P<0.01; n = 3 in each groups. The open square in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0036610#pone-0036610-g006" target="_blank">Figure 6<i>C</i></a> represents cells treated with MG; the stripped square represents cells treated with MG alagebrium. CT: control; ALA: alagebrium.</p

Effect of MG on Akt1 phosphorylation in 3T3-L1 cells.

<p>After 24 h treatment with or without MG (10 µM) in the presence or absence of SH-6 (10 µM)/alagebrium (50 µM), the protein levels of Akt1, (<b><i>A</i></b>), Representive Western blot of phospho-Akt1 (p-Akt1(Ser473), p-Akt1(thr308)) and Akt1; (<b><i>B</i></b>), The level of phospho-Akt1(Ser473) in 3T3-L1 cells with/without MG treatment; (<b><i>C </i></b>), The level of phospho-Akt1(thr308) in 3T3-L1 cells with/without MG treatment. *<i>P</i><0.05 <i>vs</i> control (CT) cells; <b>⁺</b><i>P</i><0.05 <i>vs</i> MG treated cells. The results were based on data from three experiments. CT: control; ALA: alagebrium.</p

Increased MG accumulation, reduced GSH level and glyoxalase I activity were related to Akt1 expression in obese Zucker rats.

<p>(<b><i>A</i></b>) MG levels in kidney, fat, liver of 16-week old Zucker lean or obese rats. *<i>P</i><0.05, n = 4−8 in each groups. (<b><i>B</i></b>) GSH level decreased in the adipose tissue of Zucker obese rats while glyoxalase I activity (<b><i>C </i></b>) remain unchanged compare with Zucker lean rats. GSH level was presented as % of that in control group. *P<0.05, n = 4 in each groups. (<b><i>D</i></b>) The expression of p-Akt1 and Akt1 in adipose tissue of lean and obese Zucker rats. *<i>P</i><0.05, **<i>P</i><0.01, n = 4 in both groups. The results of Western blotting were quantified by Chemigenus® Bio imaging system company) and presented as the percentage of that from control cells (<b><i>E</i></b>). □ Zucker lean rats, ▪ Zucker obese rats.</p

Effect of MG on p21, p-p21, p27, p-p27 and CDK2 activity in 3T3-L1 cells.

<p>After 24 h treatment with or without MG (10 µM) in the presence or absence of SH-6 (10 µM)/alagebrium (50 µM), the protein levels of p21, p-21 and p27, p-p27 (<b><i>A</i></b>), and the activity of Cdk2 (<b><i>B</i></b>) were determined and compared. *<i>P</i><0.05 <i>vs</i> control (CT) cells; <b>⁺</b><i>P</i><0.05 <i>vs</i> MG treated cells. The results were based on data from three experiments.</p

Basic parameters of lean/obese Zucker rats.

*<p><i>P</i><0.05,</p>**<p><i>P</i><0.01 vs lean Zucker rats, n = 4−8 in each group.</p><p>Chol: total cholesterol, TG: triglyceride, HDL: high density lipoprotein.</p