Understanding the physiological importance of amino acid transport processes in legumes

Nitrogen is essential for plant growth and development, and amino acids represent the predominant N transport forms in most plants. Transporters are required to effectively move the organic N from cell to cell and over long distances. This research addresses the functions of amino acid transporters in legumes and their importance for whole-plant physiology and productivity. Novel amino acid transporters were identified in French bean (Phaseolus vulgaris), PvAAP1, and pea (Pisum sativum) PsAAP3, PsAAP6, and PsCAT6. Functional complementation in yeast demonstrated that, with the exception of PsCAT6, they are functional transporters and mediate the growth of yeast cells on a broad spectrum of amino acids. Furthermore, expression analyses in nodules, phloem, and seeds, as well as transporter localization to the plasma membrane suggest that the transporters are involved in cellular import processes throughout the plant and that their function is highly cell-specific. The role of PsAAP6 in nodules was further analyzed by repressing PsAAP6 expression and it was found that nodule amino acid levels and development are affected in the transgenic roots. Together, our analyses of transporter function in legumes demonstrate the importance of membrane proteins in movement of amino acids in nodules, over long distances, and in import into seeds. We further examined the role of amino acid transport in plant metabolism and productivity. Transgenic pea plants expressing a yeast transporter for Smethylmethionine, a nitrogen and sulfur containing amino acid, in the phloem were produced and analyzed. Results showed that nitrogen and sulfur phloem transport as well as metabolism were affected in the transgenic plants. In addition, changes in long distance transport of nitrogen and sulfur led to an increase in total seed production and in total seed S, N and protein yields. Overall, our results demonstrate that phloem transport of S-methylmethionine is important to seed quality and quantity

Increased Phloem Transport of S-Methylmethionine Positively Affects Sulfur and Nitrogen Metabolism and Seed Development in Pea Plants

Seeds of grain legumes are important energy and food sources for humans and animals. However, the yield and quality of legume seeds are limited by the amount of sulfur (S) partitioned to the seeds. The amino acid S-methylmethionine (SMM), a methionine derivative, has been proposed to be an important long-distance transport form of reduced S, and we analyzed whether SMM phloem loading and source-sink translocation are important for the metabolism and growth of pea (Pisum sativum) plants. Transgenic plants were produced in which the expression of a yeast SMM transporter, S-Methylmethionine Permease1 (MMP1, YLL061W), was targeted to the phloem and seeds. Phloem exudate analysis showed that concentrations of SMM are elevated in MMP1 plants, suggesting increased phloem loading. Furthermore, expression studies of genes involved in S transport and metabolism in source organs, as well as xylem sap analyses, support that S uptake and assimilation are positively affected in MMP1 roots. Concomitantly, nitrogen (N) assimilation in root and leaf and xylem amino acid profiles were changed, resulting in increased phloem loading of amino acids. When investigating the effects of increased S and N phloem transport on seed metabolism, we found that protein levels were improved in MMP1 seeds. In addition, changes in SMM phloem loading affected plant growth and seed number, leading to an overall increase in seed S, N, and protein content in MMP1 plants. Together, these results suggest that phloem loading and source-sink partitioning of SMM are important for plant S and N metabolism and transport as well as seed set

Altered Xylem-Phloem Transfer of Amino Acids Affects Metabolism and Leads to Increased Seed Yield and Oil Content in Arabidopsis[W]

This work examines the amino acid transporter AAP2, which localizes to the phloem throughout the plant and is key for amino acid transfer from the xylem-phloem; mutants in AAP2 perturb nitrogen-carbon balance in the seed, affect leaf metabolism and development, and increase seed yield and oil content. Seed development and nitrogen (N) storage depend on delivery of amino acids to seed sinks. For efficient translocation to seeds, amino acids are loaded into the phloem in source leaves and along the long distance transport pathway through xylem-phloem transfer. We demonstrate that Arabidopsis thaliana AMINO ACID PERMEASE2 (AAP2) localizes to the phloem throughout the plant. AAP2 T-DNA insertion lines showed changes in source-sink translocation of amino acids and a decrease in the amount of seed total N and storage proteins, supporting AAP2 function in phloem loading and amino acid distribution to the embryo. Interestingly, in aap2 seeds, total carbon (C) levels were unchanged, while fatty acid levels were elevated. Moreover, branch and silique numbers per plant and seed yield were strongly increased. This suggests changes in N and C delivery to sinks and subsequent modulations of sink development and seed metabolism. This is supported by tracer experiments, expression studies of genes of N/C transport and metabolism in source and sink, and by phenotypic and metabolite analyses of aap2 plants. Thus, AAP2 is key for xylem to phloem transfer and sink N and C supply; moreover, modifications of N allocation can positively affect C assimilation and source-sink transport and benefit sink development and oil yield

AKAP1 Regulates Mitochondrial Dynamics during the Fatty-Acid-Promoted Maturation of Human-Induced Pluripotent Stem Cell-Derived Cardiomyocytes as Indicated by Proteomics Sequencing

Human-induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) are cells with promising applications. However, their immaturity has restricted their use in cell therapy, disease modeling, and other studies. Therefore, the current study focused on inducing the maturation of CMs. We supplemented hiPSC-CMs with fatty acids (FAs) to promote their phenotypic maturity. Proteomic sequencing was performed to identify regulators critical for promoting the maturation of hiPSC-CMs. AKAP1 was found to be significantly increased in FA-treated hiPSC-CMs, and the results were verified. Therefore, we inhibited AKAP1 expression in the FA-treated cells and analyzed the outcomes. FA supplementation promoted the morphological and functional maturation of the hiPSC-CMs, which was accompanied by the development of a mitochondrial network. Proteomic analysis results revealed that AKAP1 expression was significantly higher in FA-treated hiPSC-CMs than in control cells. In addition, increased phosphorylation of the mitochondrial dynamin Drp1 and an increased mitochondrial fusion rate were found in FA-treated hiPSC-CMs. After AKAP1 was knocked down, the level of DRP1 phosphorylation in the cell was decreased, and the mitochondrial fusion rate was reduced. FA supplementation effectively promoted the maturation of hiPSC-CMs, and in these cells, AKAP1 regulated mitochondrial dynamics, possibly playing a significant role

Disruption of the ATXN1-CIC complex causes a spectrum of neurobehavioral phenotypes in mice and humans

International audienceGain-of-function mutations in some genes underlie neurodegenerative conditions, whereas loss-of-function mutations in the same genes have distinct phenotypes. This appears to be the case with the protein ataxin 1 (ATXN1), which forms a transcriptional repressor complex with capicua (CIC). Gain of function of the complex leads to neurodegeneration, but ATXN1-CIC is also essential for survival. We set out to understand the functions of the ATXN1-CIC complex in the developing forebrain and found that losing this complex results in hyperactivity, impaired learning and memory, and abnormal maturation and maintenance of upper-layer cortical neurons. We also found that CIC activity in the hypothalamus and medial amygdala modulates social interactions. Informed by these neurobehavioral features in mouse mutants, we identified five individuals with de novo heterozygous truncating mutations in CIC who share similar clinical features, including intellectual disability, attention deficit/hyperactivity disorder (ADHD), and autism spectrum disorder. Our study demonstrates that loss of ATXN1-CIC complexes causes a spectrum of neurobehavioral phenotypes

Effects of Antiplatelet Agents on Functional Outcome and Cognitive Status in Patients with Acute Ischemic Stroke

Background: The effect of antiplatelet agents for the treatment of acute stroke is less certain than that for the treatment of acute myocardial ischemia. In this study, we investigated whether antiplatelet agents (aspirin, clopidogrel, and ozagrel) demonstrated a favorable effect on functional outcome and cognitive status 3 months poststroke. Methods: We randomly selected 24 hospitals from five different regions in China. Patients without recurrent stroke were recruited and neurological and neuropsychological examinations were performed on these patients at 3 months poststroke. Each patient was diagnosed as having favorable or poor functional outcome and normal cognition or cognitive impairment. Multivariate logistic regression analyses adjusted for sex, age, education, and neurological deficit at stroke onset were performed to examine whether antiplatelet agents exhibited a favorable effect on functional outcome and cognitive status at 3 months poststroke. Results: Of the 518 eligible patients (aged 45–86 years, mean 63.01 ± 9.99 years), 167 (32.2%) were female. On the basis of univariate analysis, there were significant associations between functional outcome (p = 0.048) and cognitive status (p = 0.026) at 3 months poststroke and the use of antiplatelet agents in acute ischemic stroke. The adjusted odds ratio for favorable functional outcome was 1.81 (95% confidence interval: 1.09–2.99) and for normal cognition 1.67 (95% confidence interval: 1.02–2.74). Conclusion: The use of antiplatelet agents in acute ischemic stroke may have a favorable effect on functional outcome and cognitive status in patients at 3 months poststroke