The Effects Of Nitrogen And Phosphrous To The Length Of Taproot And The Ability Of Rhizosphere Acidification In Arabidopsis Thaliana

Nitrogen and phosphorus are essential to the plant.They are among the least-available macronutrients required by plants.They participate widely in regulating plant growth and physiological metabolism.Nitrogen and phosphorus nutrition required for plant mainly are from rhizosphere soil to be absorbed.When nitrogen and phosphorus are deficient in the rhizosphere soil,plants improve the absorption and utilization efficiency of nitrogen and phosphorus nutrition by changing its own root morphology and physiological and biochemical metabolism process to adapt to the stress of nitrogen and phosphorus nutrition.However,the molecular mechanism of rhizosphere state of nitrogen and phosphorus is not very clear.Our laboratory obtains the related to nitrogen and phosphorus nutrition respectively Arabidopsis mutants through the screening of mutants library.We look forward to understanding the molecular mechanism of plant to adapt to the stress of nitrogen and phosphorus nutrition.The characteristics of short root mutant sr883 analysis in Arabidopsis thaliana:sr883 is from EMS mutagenesis screening of mutants of Arabidopsis short root.PI dyeing shows that sr883 mutant taproot apical quiescent center stem cells dysplasia,the number of cells significantly reduces in the areas of meristematic,elongation zone cells significantly shorten the length.Under the condition of lack of ammonium nitrogen,sr883 mutant mains spikes long recovered greatly and ammonium nitrogen restrained the growth of the taproot when the mount of ammonium was too much.Therefore,sr883 is nitrogen nutrition regulation of root development in Arabidopsis mutants.Map-based cloning analysis shows that sr883 located in the top five chromosome.The lacking of At5g05980 genetic encoding area 2019 bp bases,caused sr883 showed shorter taproot phenotype.A semi-quantitative PCR analysis shows that lack of ammonium increased SR883 gene expression.GUS staining of tissue characterization and GFP fusion protein subcellular localization of the analysis show that SR883 gene have been expressed in plants of various organizations.Its coding protein distribution in different parts of the cytoplasm.We use containing auxin indicator DR5::GFP and DR5::GUS to hybrid with sr883 respectively.We got sr883:DR5:GFP and sr883:DR5:GUS homozygous Arabidopsis thaliana.Experiments showed that the lack of ammonium treatment enhanced obviously sr883:DR5:GFP intensity of fluorescence.The staining of sr883:DR5:GUS obviously increased.The lack of ammonium treatment can increase sr883 root auxin concentration.SR883 gene expression is induced by the lack of ammonium,then promote the auxin content in root.This is an opportunity to clear the molecular mechanism of root growth under the lack of ammonium treatment.The p444 is our laboratory obtained by low phosphorylated screening mutants.Under the condition of low phosphorus stress,p444 showed rhizosphere acidification missing phenotype.This shows p444 is related to soil uptake phosphorus.Map-based cloning for p444,we found its mutation site is at At5g04140.The gene encodes glutamate synthase in plants and involves in GS-GOGAT circulation.The gene can use alpha-ketone glutaric acid and glutamine synthesis glutamic acid,adjust the assimilation of nitrogen.Gene P444 influence the balance of small organic molecules,such as alpha-ketone glutaric acid,glutamate,glutamine.In order to verify circulation of GS-GOGAT whether related small molecules involved in regulating p444 under low phosphorus induced rhizosphere acidification.We added sucrose,glucose,alpha-ketone glutaric acid,glutamate and glutamine in rhizosphere to explore influence of rhizosphere acidification.The results showed that low concentration(50 ?M)glutamine can make the wild-type Arabidopsis rhizosphere acidification capacity reduce.This result is similar to phenotype of p444 mutant under low phosphorus stress.Thus we speculate the accumulation of glutamine may make p444 lack of rhizosphere acidification.By combining the above small molecules to low phosphorylation reaction,we found in all of acidification reaction,the experimental results are always consistent with the result of adding glutamine alone.This shows that glutamine plays a leading role in the rhizosphere acidification reaction induced by low phosphorus.According to the previous studies,the P444 located where part is mainly expressed in the ground.So we suspected p444 via remote control to adjust the rhizosphere acidification reaction induced by low phosphorus.Further through the graft,we found the local upper into the wild type,low phosphorus under the condition of rhizosphere acidification is enhanced;while the local is divided into upper mutant,under the condition of low phosphorus rhizosphere acidification is reduced.This has nothing to do with whether the root is from the wild type or mutant.Therefore we believe that the aboveground part of plant plays an important role under the condition of low phosphorus rhizosphere acidification.In order to verifythe accumulation of glutamine effects on rhizosphere acidification,we design an experiment of the petiole incision.Adding glutamine in petiole slit can reduce the Arabidopsis rhizosphere acidification induced by low phosphorus intensity.By measuring the content of glutamine under low phosphorus condition of wild type and mutant,we found that after treated with low phosphorus,the glutamine content change of underground is obvious.Therefore,we think the rhizosphere acidification of p444 mutant is likely to be the lack of glutamate synthesis function.The accumulation of glutamine as long distance signal molecular regulats of the rhizosphere acidification reaction induced by low phosphorus.