Nitrogen Absorption and Assimilation in Plants PDF

22/01/2020 Nitrogen: One of the most abundant mineral element in a plant The most abundant element in the...

22/01/2020 Nitrogen: One of the most abundant mineral element in a plant The most abundant element in the earth’s atmosphere The 4th most abundant element in a plant (after C, H and O) Often the limiting nutrient for plant growth N is in amino acids (proteins), nucleic acids (DNA, RNA), chlorophyll, and countless small molecules Nitrogen is one of the three major macronutrients found in most fertilizers Blank, L.M. (2012). The cell and P: From cellular function to biotechnological application. Curr. Opin. Biotech. 23: 846 – 851.From: Buchanan, B.B., Gruissem, W. and Jones, R.L. (2000) Biochemistry and Molecular Biology of Plants. American Society of Plant Physiologists. Localisation de l’absorption des ions huile Eau minérale ------> Les poils absorbants sont indispensables à l’absorption des minéraux 1  22/01/2020 Vascular plants assimilate mineral nutrients mostly via roots By increasing surface area for absorption, root hairs functionally resemble microvilli of an animal’s intestinal epithelium Membrane transporters facilitate nutrient uptake Barberon, M. and Geldner, N. (2014). Radial transport of nutrients: the plant root as a polarized epithelium. Plant Physiol. 166: 528-537. Roots have several adaptations to enhance nutrient capture Biochemical Developmental responses responses Fungal symbiotic Prokaryotic partners symbiotic partners Schmidt, S., Raven, J.A. and Paungfoo-Lonhienne, C. (2013). The mixotrophic nature of photosynthetic plants. Funct. Plant Biol. 40: 425-438 by permission of CSIRO publishing. 2  22/01/2020 Plants have specific transporters for NO3-, NH4+ and other N forms HATS = high affinity transporters LATS = low affinity transporters Nacry, P., Bouguyon, E. and Gojon, A. (2013). Nitrogen acquisition by roots: physiological and developmental mechanisms ensuring plant adaptation to a fluctuating resource. Plant Soil. 370: 1-29, With kind permission from Springer Science and Business Media 3  22/01/2020 NH4+ NH4+ H+ H+ 4  22/01/2020 2132 5  22/01/2020 Avantage de la nutrition mixte (NH4 + NO3) 6  22/01/2020 Ammonisation Ammonium, Ammoniac, Ammoniaque (NH4+, NH3, NH4OH) AMMONISATION Bacillus subtilis 7  22/01/2020 NITRIFICATION MISE EN EVIDENCE DE LA REDUCTION DU NITRATE NO2 (36h) NO3 (24h) Asparagine (48h) NO3 8  22/01/2020 ORIGINE DES COFACTEURS NITRATE REDUCTASE NITRITE REDUCTASE ( NR) (NIR) NADH NADPH REDUCTION DU NITRATE EN AMMONIUM NR : nitrate réductase NiR : nitrite réductase VACUOLE NO3 PLASTE NO3 NO3 NiR NR NO2 NH4+ NO2 NR NO3- + NADH + 2H+ + 2 e- NO2- + NAD+ + 2H2O NiR NO2- + 6 Ferrred + 6H+ + 6 e- NH3 + 6 Ferrox + H2O + OH- 9  22/01/2020 STRUCTURE DE LA NITRATE REDUCTASE 10  22/01/2020 RT-PCR Northern Blot _ N NR NiR qRT-PCR quantitative NR Quantité relative 10 NiR NiR NR 1 _ N REGULATION DE LA NITRATE REDUCTASE PAR LE SUBSTRAT 11  22/01/2020 REGULATION DE LA NITRATE REDUCTASE PAR LA LUMIERE REGULATION DE LA NITRATE ET DE LA NITRITE REDUCTASE PAR DIFFERENTS FACTEURS 12  22/01/2020 LA GLUTAMINE SYNTHASE (GS) ISOFORMES ET ADRESSAGE 13  22/01/2020 FACTEURS DE REGULATION DE LA GS DU NITRATE A LA GLUTAMINE VACUOLE NO3 PLASTE NiR NO2 NO2 NH4+ + Glu a-céto- GS-2 glutarate NR GDH NO3 NO3 2 Glu Gln + a-céto- glutarate GOGAT GS-1 Gln NH4+ + Glu NR : nitrate réductase GS : glutamine synthase GDH : glutamate déshydrogénase NiR : nitrite réductase GOGAT : glutamine oxoglutarate amido transférase 14  22/01/2020 BIOSYNTHESE DES ACIDES AMINES LA TRANS-AMINATION Acide aspartique et acide glutamique COOH HCO3- Pi COOH C OPO32- C O CH2 CH2 COOH Phosphoenol – pyruvate (PEP) Acide oxalo- acétique (AOA) COOH COOH COOH HC NH2 HC NH2 C O Transamination AOA + + (CH2)2 CH2 (CH2)2 COOH COOH COOH Acide glutamique Acide aspartique Acide a-cetoglutarique 15  22/01/2020 LUMIÈRE ET RÉGULATION DE LA BIOSYNTHÈSE DE L’ASPARAGINE Glutamine + aspartate Light Dark Asparagine 40 synthétase % total amino acid Asparagine + glutamate 30 20 10 0 WT aat2 WT aat2 ASPARTATE ASPARAGINE BIOSYNTHÈSE DE L’ASPARAGINE 16  22/01/2020 VUE D’ENSEMBLE DE LA BIOSYNTHÈSE DES ACIDES AMINÉS BIOSYNTHÈSE DES ACIDES AMINÉS AROMATIQUES VOIE DU SHIKIMATE Shikimate Pi Pi PEP Shikimate-3-P Chorismate 17  22/01/2020 BIOSYNTHÈSE DE LA PHÉNYLALANINE ET DE LA TYROSINE 18