Physiological Response Of Mn Hyperaccumulator Schima Wallichii To Mn Stress And Metabolics And Transcriptomics Analysis

There are abundant manganese ore resources in China.And mining and smelting of manganese ore increased the risk of manganese pollution in soil.Manganese is an essential trace element for creature,but excess manganese can inhibit crops growth,and endanger human being's health.The amount of heavy metals in soil can be reduced through plants' absorbance and transferation,which is a kind of green environmental remediation technology.Woody plants have high biomass and long life cycle,and those are unique advantages in the phytoremediation of heavy metal.But the capacity of woody plants to accumulate heavy metals is usually very low,and most of heavy metal is accumulated in the roots of woody plants.Through sand culture,a new manganese hyperaccumulator,Schima wallichii,was found.And this species has a good applicantion prospect in the phytoremedation of manganese pollution.In the thesis,one-year old seedlings of S.wallichii were treated with 50 mmol/L and 100 mmol/L Mn respectively.And the physiological responses and changes in metabolic path and gene expression were investigated with physiological and biochemical methods,metabonomics and genomics.The main conclusions are as followed:1.After being treated for one month,Mn concentrations in roots,stems and leaves of S.wallichii apparently increased with Mn treatment concentrations rising.The Mn concentration in leaves of S.wallichii under 100 mmol/L Mn reached 10946.3 mg/kg,what is more,both Mn translocation factor and the root tolerance index of S.wallichii were greater than 1,which indicated that S.wallichii is a Mn hyperaccumulator.The Mg,Ca,Fe,Cu,K and Zn concentrations in stems and leaves of S.wallichii were not markedly influnced by Mn treatments.But the concentrations of Fe,Cu and Zn in roots of S.wallichii under Mn treatments were significantly improved.After being treated for 6d,MDA content in leaves of S.wallichii did not change apparently,and SOD activity decreased,but CAT and POD activities notably rose.It demonstrated that CAT and POD play important roles in S.wallichii resisting to Mn stress.Malic acid obviously decreased Mn concentration in leaves and translocation factor of S.wallichii under 100mmol/L Mn treatment.Simultaneously,the concentrations of Fe,Cu and Zn in roots of S.wallichii under 100mmol/L Mn had declining tendencies.2.The relative concentrations of organic small molecular substances in leaves of S.wallichii under Mn stress were measured with Gas Chromatography-Mass Spectrography(GC-MS).Metabolic changes were analyzed through the unsupervised principal component analysis(PCA)and supervised partial least squares-discriminant analysis(PLS-DA).It was found that the metabolic pathways of aspartate amino acids family responsing for lysine biosynthesis associates with several energy metabolism pathways,and play multiple roles in plant metabolism.The content of the amono acids in the lysine metabolic pathway under high Mn stress(100 mmol/L Mn)was higher than those of control.The soluble lysine concentration in 100mmol/L Mn treatment significantly increased compared with the control.Meanwhile,the concentrations of soluble amino acids involved in lysine biosynthesis,such as aspartic acid,threonine,methionine and isoleucine,also elevated to various extents.According to database NIST,78 metabolites which changed significantly under Mn stress were indentified(VIP > 1).And 18 substances among them belong to amino acids.The following amino acids increased dramtically under Mn stress: Amino acids in proline metabolic pathway(ornithine,glutamate and proline),in lysine metabolic pathway(methionine,lysine aspartic acid,threonine and isoleucine)and in aromatic amino acid pathway(tyrosine and phenylalanine),which indicated that the three metabolic pathways play significant roles in S.wallichii resisting to Mn stress.3.The transcriptome of S.wallichii leaves of CK and 100mmol/L treatment were de novo sequenced.The results demonstrated that 119 unigenes were up-regulated and 145 unigenes were down-regulated in the leaves of S.wallichii under 100mmol/L Mn treatment.By KEGG pathway analysis,the gene encoding shikimic acid dehydrogenase,which is involved in biosynthesis of phenylalanine,tyrosine,and tryptophan was upregulated under Mn treatment.This result deciphered the concentrations of tyrosine and phenylalanine increase in the leaves of S.wallichii treated by Mn.