Outline

  • Abstract
  • Keywords
  • 1. Introduction
  • 2. Serine, a Key Regulator for Development?
  • 2.1. Serine, an Indispensable Metabolite
  • 2.2. Serine, a Metabolic Signal?
  • 3. Gaba Signaling in Plants
  • 3.1. Putative Plant Gaba Receptors
  • 3.2. the Role of Gaba in Plant Sexual Reproduction
  • 3.3. Gaba and Cell Elongation
  • 3.4. a Role for Gaba in Patterning and Cell Identity
  • 4. Signal Molecules Deriving from Aromatic Amino Acids
  • 4.1. Phosphoenolpyruvate, an Important Link Between Primary Metabolism and Aromatic Amino Acid-Based Signaling
  • 4.2. Lignans and Neolignans Deriving from Phenylpropanoid Metabolism Act As Signal Molecules
  • 4.3. Transgenic and Mutant Plants with Impaired Neolignan Signaling
  • 4.4. Hydroxycinnamic Acid Amides (hcaa) As Metabolic Signals
  • 4.5. Hcaas Have Multiple Functions in Plants and Mammalians
  • 5. Conclusions and Future Perspectives
  • 5.1. Serine
  • 5.2. Gaba
  • 5.3. Phenylpropanoids and Hcaas
  • Acknowledgements
  • References

رئوس مطالب

  • چکیده
  • کلید واژه ها
  • 1.مقدمه
  • 2.سرین، تنظیم کننده اصلی برای رشد و نمو و توسعه؟
  • 2.1 سرین، یک متابولیت ضروری
  • 2.2 سرین، یک سیگنال متابولیکی است؟
  • 3. سیگنال دهی GABA گابا در گیاهان
  • 3.1 گیرنده های گیاهی فرضی گابا
  • 3.2 نقش گابا در تولید مثل جنسی گیاهان
  • 3.3 گابا و طویل شدن سلول
  • 3.4 نقش گابا در الگودهی و هویت سلولی
  • 4. مولکولهای سیگنالی مشتق شده از اسیدهای آمینه آروماتیک
  • 4.1 فسفوانول پیروات، یک رابط مهم میان متابولیسم اولیه و سیگنالینگ اسید آمینه های آروماتیک
  • 4.2 لیگنان ها و نئو لیگنان های مشتق شده از متابولیسم فنیل پروپانوئید، که به عنوان مولکولهای سیگنالی عمل می کنند
  • 4.3 گیاهان ترانسژنیک و جهش یافته همراه با اختلال سیگنال دهی نئو لیگنان
  • 4.4 آمیدهای اسید هیدروکسی سینامیک (HCAA) به عنوان سیگنال های متابولیکی
  • 4.5 HCAAs، اعمال متعددی در گیاهان و پستانداران دارد
  • 5. نتیجه گیری و دیدگاه های آینده
  • 5.1 سرین
  • 5.2 GABA
  • 5.3 فنیل پروپانوئیدها و HCAAs

Abstract

Amino acids serve as constituents of proteins, precursors for anabolism, and, in some cases, as signaling molecules in mammalians and plants. This review is focused on new insights, or speculations, on signaling functions of serine, γ-aminobutyric acid (GABA) and phenylalanine-derived phenylpropanoids. Serine acts as signal in brain tissue and mammalian cancer cells. In plants, de novo serine biosynthesis is also highly active in fast growing tissues such as meristems, suggesting a similar role of serine as in mammalians. GABA functions as inhibitory neurotransmitter in the brain. In plants, GABA is also abundant and seems to be involved in sexual reproduction, cell elongation, patterning and cell identity. The aromatic amino acids phenylalanine, tyrosine, and tryptophan are precursors for the production of secondary plant products. Besides their pharmaceutical value, lignans, neolignans and hydroxycinnamic acid amides (HCAA) deriving from phenylpropanoid metabolism and, in the case of HCAA, also from arginine have been shown to fulfill signaling functions or are involved in the response to biotic and abiotic stress. Although some basics on phenylpropanoid-derived signaling have been described, little is known on recognition- or signal transduction mechanisms. In general, mutant- and transgenic approaches will be helpful to elucidate the mechanistic basis of metabolite signaling.

Keywords: - - - -

Conclusions

The function of l-serine as signaling molecule is currently subject of intense debate in the fields of cancer research and plant biology. In proliferating cancer cells, l-serine has been identified as a regulator of TOR kinase activity. In plants, the ‘phosphorylated’ serine and the TOR pathways are highly active in meristems. A regulation of TOR kinase by l-serine similar to the mammalian system can be assumed and would hence represent a promising target for future studies on the signaling function of l-serine.

The activity of TOR kinase is usually measured as change in the phosphorylation state of its target protein, i.e. the ribosomal S6 kinase, by antibodies specific for the phosphorylation site. In turn, the S6 kinase phosphorylates the ribosomal protein S6, a critical component of the 40S ribosomal subunit. A possible impact of l-serine on TOR kinase activity could be studied by determination of the S6 kinase phosphorylation state either after treatment of plants with physiological concentrations of l-serine or in plants deficient in the ‘phosphorylated’ serine biosynthesis pathway. This approach would not only shed light on the question if l-serine is a signaling molecule in plants, but it would also help to understand how growth and development is regulated by metabolite signals in plants.

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