The aromatic amino acids phenylalanine, tyrosine, and tryptophan in plants are not only essential components of protein synthesis, but also serve as precursors for a wide range of secondary metabolites that are import...The aromatic amino acids phenylalanine, tyrosine, and tryptophan in plants are not only essential components of protein synthesis, but also serve as precursors for a wide range of secondary metabolites that are important for plant growth as well as for human nutrition and health. The aromatic amino acids are synthesized via the shikimate pathway followed by the branched aromatic amino acids biosynthesis pathway, with chorismate serving as a major intermediate branch point metabolite. Yet, the regulation and coordination of synthesis of these amino acids are still far from being understood. Recent studies on these pathways identified a number of alternative cross-regulated biosynthesis routes with unique evolutionary origins. Although the major route of Phe and Tyr biosynthesis in plants occurs via the intermediate metabolite arogenate, recent studies suggest that plants can also synthesize phenylalanine via the intermediate metabolite phenylpyruvate （PPY）, similarly to many microorganisms. Recent studies also identified a number of transcription factors regulating the expression of genes encoding enzymes of the shikimate and aromatic amino acids pathways as well as of multiple secondary metabolites derived from them in Arabidopsis and in other plant species. .展开更多
Plant take up the essential nutrient sulfur as sulfate from the soil, reduce it, and assimilate into bioorganic compounds, with cysteine being the first product. Both sulfate uptake and assimilation are highly regulat...Plant take up the essential nutrient sulfur as sulfate from the soil, reduce it, and assimilate into bioorganic compounds, with cysteine being the first product. Both sulfate uptake and assimilation are highly regulated by the demand for the reduced sulfur, by availability of nutrients, and by environmental conditions. In the last decade, great prog- ress has been achieved in dissecting the regulation of sulfur metabolism. Sulfate uptake and reduction of activated sulfate, adenosine 5＇-phosphosulfate （APS）, to sulfite by APS reductase appear to be the key regulatory steps. Here, we review the current knowledge on regulation of these processes, with special attention given to similarities and differences.展开更多
Plants are either directly or indirectly the source of most of the essential amino acids in animal diets. Four of these essential amino acids--methionine, threonine, isoleucine, and lysine--are all produced from aspar...Plants are either directly or indirectly the source of most of the essential amino acids in animal diets. Four of these essential amino acids--methionine, threonine, isoleucine, and lysine--are all produced from aspartate via a well studied biosynthesis pathway. Given the nutritional interest in essential amino acids, the aspartate-derived amino acid pathway has been the subject of extensive research. Additionally, several pathway enzymes serve as targets for econom- ically important herbicides, and some of the downstream products are biosynthetic precursors for other essential plant metabolites such as ethylene and S-adenosylmethionine. Recent and ongoing research on the aspartate-derived family of amino acids has identified new enzyme activities, regulatory mechanisms, and in vivo metabolic functions. Together, these discoveries will open up new possibilities for plant metabolic engineering.展开更多
Continuous increase of wind power penetration brings high randomness to power system,and also leads to serious shortage of primary frequency regulation(PFR)reserve for power system whose reserve capacity is typically ...Continuous increase of wind power penetration brings high randomness to power system,and also leads to serious shortage of primary frequency regulation(PFR)reserve for power system whose reserve capacity is typically provided by conventional units.Considering large-scale wind power participating in PFR,this paper proposes a unit commitment optimization model with respect to coordination of steady state and transient state.In addition to traditional operation costs,losses of wind farm de-loaded operation,environmental benefits and transient frequency safety costs in high-risk stochastic scenarios are also considered in the model.Besides,the model makes full use of interruptible loads on demand side as one of the PFR reserve sources.A selection method for high-risk scenarios is also proposed to improve the calculation efficiency.Finally,this paper proposes an inner-outer iterative optimization method for the model solution.The method is validated by the New England 10-machine system,and the results show that the optimization model can guarantee both the safety of transient frequency and the economy of system operation.展开更多
Sulfur is essential for plant growth and development, and the molecular systems for maintaining sulfur and thiol metabolism are tightly controlled. From a biochemical perspective, the regulation of plant thiol metabol...Sulfur is essential for plant growth and development, and the molecular systems for maintaining sulfur and thiol metabolism are tightly controlled. From a biochemical perspective, the regulation of plant thiol metabolism high- lights nature＇s ability to engineer pathways that respond to multiple inputs and cellular demands under a range of con- ditions. In this review, we focus on the regulatory mechanisms that form the molecular basis of biochemical sulfur sensing in plants by translating the intracellular concentration of sulfur-containing compounds into control of key metabolic steps. These mechanisms range from the simple （substrate availability, thermodynamic properties of reactions, feedback inhi- bition, and organelle localization） to the elaborate （formation of multienzyme complexes and thiol-based redox switches）. Ultimately, the dynamic interplay of these regulatory systems is critical for sensing and maintaining sulfur assimilation and thiol metabolism in plants.展开更多
文摘The aromatic amino acids phenylalanine, tyrosine, and tryptophan in plants are not only essential components of protein synthesis, but also serve as precursors for a wide range of secondary metabolites that are important for plant growth as well as for human nutrition and health. The aromatic amino acids are synthesized via the shikimate pathway followed by the branched aromatic amino acids biosynthesis pathway, with chorismate serving as a major intermediate branch point metabolite. Yet, the regulation and coordination of synthesis of these amino acids are still far from being understood. Recent studies on these pathways identified a number of alternative cross-regulated biosynthesis routes with unique evolutionary origins. Although the major route of Phe and Tyr biosynthesis in plants occurs via the intermediate metabolite arogenate, recent studies suggest that plants can also synthesize phenylalanine via the intermediate metabolite phenylpyruvate （PPY）, similarly to many microorganisms. Recent studies also identified a number of transcription factors regulating the expression of genes encoding enzymes of the shikimate and aromatic amino acids pathways as well as of multiple secondary metabolites derived from them in Arabidopsis and in other plant species. .
文摘Plant take up the essential nutrient sulfur as sulfate from the soil, reduce it, and assimilate into bioorganic compounds, with cysteine being the first product. Both sulfate uptake and assimilation are highly regulated by the demand for the reduced sulfur, by availability of nutrients, and by environmental conditions. In the last decade, great prog- ress has been achieved in dissecting the regulation of sulfur metabolism. Sulfate uptake and reduction of activated sulfate, adenosine 5＇-phosphosulfate （APS）, to sulfite by APS reductase appear to be the key regulatory steps. Here, we review the current knowledge on regulation of these processes, with special attention given to similarities and differences.
文摘Plants are either directly or indirectly the source of most of the essential amino acids in animal diets. Four of these essential amino acids--methionine, threonine, isoleucine, and lysine--are all produced from aspartate via a well studied biosynthesis pathway. Given the nutritional interest in essential amino acids, the aspartate-derived amino acid pathway has been the subject of extensive research. Additionally, several pathway enzymes serve as targets for econom- ically important herbicides, and some of the downstream products are biosynthetic precursors for other essential plant metabolites such as ethylene and S-adenosylmethionine. Recent and ongoing research on the aspartate-derived family of amino acids has identified new enzyme activities, regulatory mechanisms, and in vivo metabolic functions. Together, these discoveries will open up new possibilities for plant metabolic engineering.
基金supported by the Six Talent Peaks Project in Jiangsu Province(No.XNY-020)the State Key Laboratory of Smart Grid Protection and Control
文摘Continuous increase of wind power penetration brings high randomness to power system,and also leads to serious shortage of primary frequency regulation(PFR)reserve for power system whose reserve capacity is typically provided by conventional units.Considering large-scale wind power participating in PFR,this paper proposes a unit commitment optimization model with respect to coordination of steady state and transient state.In addition to traditional operation costs,losses of wind farm de-loaded operation,environmental benefits and transient frequency safety costs in high-risk stochastic scenarios are also considered in the model.Besides,the model makes full use of interruptible loads on demand side as one of the PFR reserve sources.A selection method for high-risk scenarios is also proposed to improve the calculation efficiency.Finally,this paper proposes an inner-outer iterative optimization method for the model solution.The method is validated by the New England 10-machine system,and the results show that the optimization model can guarantee both the safety of transient frequency and the economy of system operation.
基金This work was funded by grants from the US Department of Agriculture （NRI-2005-02518） and the National Science Foundation （MCB-0824492）. No conflict of interest declared.
文摘Sulfur is essential for plant growth and development, and the molecular systems for maintaining sulfur and thiol metabolism are tightly controlled. From a biochemical perspective, the regulation of plant thiol metabolism high- lights nature＇s ability to engineer pathways that respond to multiple inputs and cellular demands under a range of con- ditions. In this review, we focus on the regulatory mechanisms that form the molecular basis of biochemical sulfur sensing in plants by translating the intracellular concentration of sulfur-containing compounds into control of key metabolic steps. These mechanisms range from the simple （substrate availability, thermodynamic properties of reactions, feedback inhi- bition, and organelle localization） to the elaborate （formation of multienzyme complexes and thiol-based redox switches）. Ultimately, the dynamic interplay of these regulatory systems is critical for sensing and maintaining sulfur assimilation and thiol metabolism in plants.
