1 Nutrients Katerina Dadakova, Department of Biochemistry Figures adopted from Buchanan et al., Biochemistry & molecular biology of plants Nutrients Essential mineral nutrients Nutrients Potassium K+ is the most abundant cellular cation K+ functions: •osmoticum •charge balance •enzyme activation Nutrients Compound Oxidation state of N Name N2 0 Dinitrogen (nitrogen gas) HN3 -3 Ammonia NH4+ -3 Ammonium ion N2O +1 Nitrous oxide NO +2 Nitric oxide NO2- +3 Nitrite NO2 +4 Nitrogen dioxide NO3- +5 Nitrate Nitrogen nitrogen fixation glutamine synthetase N2 NH4+ Glutamine Organic nitrogen compounds Glutamate Selected organic nitrogen compounds Nitrogen deficiency phenotype Nutrients Plants may acquire N as: • ammonium ion •nitrate •dinitrogen, only in the case of plant species capable of endosymbiosis with nitrogen-fixing bacteria • Obtaining nitrogen through symbiosis consumes 12 to 17 g of carbohydrate per gram of N fixed Nutrients Nitrogen fixation N2 + 16ATP + 8e- + 8H+ 2NH3 + H2 + 16ADP + 16Pi Nitrogenase complex Dinitrogenase reductase Fe protein Dinitrogenase MoFe protein Nutrients An external file that holds a picture, illustration, etc. Object name is nihms171659f1.jpg Object name is nihms171659f1.jpg Legume-rhizobial symbiosis The plant creates root nodules to ensure: •microaerobic environment •organic acids to feed the bacteria •carbon skeletons to transport fixed nitrogen • Bacterial symbionts fix nitrogen and release the resulting ammonia • • 1.Plant signals 2.Nod factors 3.Nodulin proteins Nutrients Nodule morphogenensis In symbiosomes, bacteria differentiate into bacteroids Nutrients Microaerobic nodule environment is created Carbon is provided to the bacteroids as dicarboxylic acids •oxidation of DCA provides ATP •DCA carbon backbones are used for nitrogen transport Nutrients Ammonia assimilation GS-GOGAT cycle Nutrients Nitrate assimilation Nutrients Nitrate reductase NR homodimer NR reaction NO3- + NAD(P)H + H+ NO2- + NAD(P)+ + H2O FAD Heme -Fe MoCo Hinge II Hinge I NAD(P)H NAD(P)+ NO3- NO2- Nutrients Nitrite reductase NiR reaction NO2- + 6 Fdxred + 8 H+ NH4+ + 6 Fdxox + 2 H2O Nutrients Regulation of nitrate assimilation hours of nitrate exposure days Nutrients Sulfur APS – 5-adenylylsulfate PAPS – 3´phosphoadenosine-5´-phosphosulfate, Nutrients Phytochelatin molecule Nutrients Coenzyme A Thiamine pyrophosphate Nutrients Nutrients Sulfate activation Nutrients Sulfate reduction to sulfide Nutrients Cysteine synthesis Nutrients Regulation of sulfate assimilation • Sulfur assimilation is not strongly regulated by light the enzymes are also active in etiolated plants and do not demonstrate diurnal oscillations • • Sulfur assimilation is regulated by developmental stage all the enzymes are highly active in young leaves and root tips • • Sulfur assimilation is regulated in response to the availability of sulfur sulfur starvation results in the up-regulation of sulfate transport and APS reductase • The content of reduced sulfur and nitrogen is strictly coordinated • Sulfite and sulfide are not allowed to accumulate Nutrients Phosphorus Nutrients Phosphate functions: •component of nucleic acids and phospholipids •energy conversion (ATP) •regulation Endomycorrhizae Root modifications in low Pi concentration, days