Isopentenyl pyrophosphate isomerase（IPP） is responsible for the reversible isomerization of isopentenyl pyrophosphate and dimethylallylpyrophosphate（DMAPP）， playing an important role in the biosynthesis of downstream terpenoid products. In this paper， 31 IPP genes were identified from genomes of various mono- and dicotyledonous plants such as Oryza sativa and Arabidopsis thaliana by bioinformatics method. Phylogenetic analysis indicated that these IPPs were divided into three clades， in which those from monocotyledon plants formed a monophyletic clade. IPPs within the same clade shared similar domains and might have similar biological functions. The analysis on cis-regulatory elements of O. sativa and A. thaliana IPP genes exhibited multiple response elements such as drought response elements. Finally， quantitative PCR results showed that the expression patterns of IPP transcription levels in O. sativa and A. thaliana were diversified. These above results provided theoretical basis for systematic understanding and further application of IPPs.

In order to explore the genetic background of tulip germplasm resources， accurately evaluate and screen excellent germplasm for genetic improvement of tulips， the genetic background of 40 tulip varieties was analyzed by SRAP molecular markers， and their genetic diversity and relationships were clarified， respectively. The results showed that out of 43 pairs of SRAP primers， 21 pairs of polymorphic primers were available for genetic diversity analysis of tulips， and 249 clear and stable bands were amplified in the 40 tulip varieties， of which 245 were polymorphic bands with a polymorphism rate of 98.39%. The genetic similarity index of the 40 tested varieties ranged from 0.502 0 to 0.867 5， and the genetic diversity parameters including the number of alleles（N_{\mathrm{a}}^{\mathrm{*}}）， number of effective alleles（N_{\mathrm{e}}^{\mathrm{*}}）， Nei’s gene diversity index（H^*）， Shannon’s information index（I^*）， and polymorphic information content were 1.981 0， 1.514 9， 0.304 2， 0.460 3， and 0.321 2， resp-ectively， indicating rich genetic diversity in the tested materials. Cluster analysis and principal coordinate analysis showed that the 40 tulip varieties were classified into two major groups， among which ‘Christmas Magical’， ‘Banja Luka’， and ‘Madame Lefeber’ were relatively distant genetic relationships from other varieties and had certain differences in their genetic backgrounds.

In order to explore the metabolic mechanism of Lanzhou lily（Lilium davidii var. unicolor） in response to autotoxicity stress， one-year-old（Lily1）， two-year-old（Lily2） and three-year-old（Lily3） Lanzhou lilies were used as materials， and gas chromatography-mass spectrometry（GC-MS） was used to analyze the metabolomic changes of Lanzhou lily under continuous cropping years， and a total of 124 metabolites were detected and identified. R software was used to normalize the samples， and orthogonal partial least squares discriminant analysis（OPLS-DA） was used to find differential metabolites， and related metabolite pathways were screened for joint analysis. The results showed that there were 16 differential metabolites（lipids， flavonoids， saccharides and phenols） between Lily1 and Lily2， and all of them were up-regulated； and it was significantly enriched in tyrosine metabolism， propionic acid metabolism and flavonoid biosynthetic metabolic pathways. The contents of lipids， flavonoids and saccharides increased， indicating that in the second year of continuous cropping， Lanzhou lily responded to autotoxicity stress by actively synthesizing lipids， flavonoids and saccharides. There were 21 differential metabolites between the metabolomes of Lily1 and Lily3， including one up-regulated metabolite（3-α-mannobiose） and 20 down-regulated metabolite packages （amines， acids， and lipids）； and five metabolic pathways were significantly enriched， including biosynthesis of tropane， piperidine and pyridine alkaloids， phosphate and hypophosphite metabolism， lysine degradation， glutathione metabolism and D-amino acid metabolism. There were 21 differential metabolites between Lily2 and Lily3 groups， and the only up-regulated metabolite was 3-α-mannobiose. The results showed that in the third year of continuous cropping of Lanzhou lily， saccharides， as carbohydrates， were directly involved in cell membrane stability， actively responded to autotoxicity stress. The 20 down-regulated metabolites were amines， acids and lipids； only the propionic acid metabolism and flavonoid biosynthetic metabolism pathways were significantly enriched.

Ribulose-1，5-diphosphate carboxylase/oxygenase（Rubisco） is a key enzyme in photosynthesis， in which small subunits（rbcS） are encoded by nuclear genes and mainly expressed in leaves. In this study， the Rubisco small subunit genes PxrbcS1 and PxrbcS2， which are highly expressed in Populus × xiaohei’s leaves， were determined by RT-qPCR technology， and their upstream promoters of 2 240 and 2 174 bp were cloned respectively. The results of promoter element analysis showed that the promoters of PxrbcS1 and PxrbcS2 had multiple elements related to light induced expression， including G-box， MRE and Box4 elements. Plant expression vectors of pBI-121-pPxrbcS1：：GUS and pBI-121-pPxrbcS2：：GUS were constructed and genetically transformed into 84K poplar（P. alba×P. glandulosa）. GUS histochemical staining and qPCR expression analysis showed that the promoters of PxrbcS1 and PxrbcS2 could drive the GUS gene to express in 84K poplar leaves with high specificity. In conclusion， the above results showed that PxrbcS1 and PxrbcS2 promoters with high leaf expression activity were successfully cloned from P.×xiaohei， and the promoters might be applied to the study of gene functions related to plant photosynthesis and genetic operations to improve photosynthesis in plants， including poplars.

Psathyrostachys juncea was considered an important ancestral species of Leymus. The genomic Cot-1 DNA library with highly repeat sequences of Psa. juncea was constructed， and sequenced and characterized， and the results showed that the library could be classified into six types： retrotransposons， transposons， satellite DNA， LZ-NBS-LRR， uncharacterized sequences， and retrotransposon LTR mixed LTR/Copia， and the proportions were 49.5%， 1.0%， 28.7%， 5.9%， 13.9% and 1.0% of the Cot-1 DNA， respectively. Furthermore， two satellite DNAs and five retrotransposon sequences were used as probes， and chromosomes in Psa. juncea， Leymus secalinus and L. racemosus were detected by florescence in situ hybridization （FISH）. The results showed that the hybridization signals of satellite DNA sequences TaiI-family and pSc250-family were mainly distributed at the ends of chromosomes， and the number of TaiI-family hybridization signals were 20， 16， 7， and 18 in Psa. juncea， L. secalinus， L. racemosus （PI 531811） and L. racemosus （PI 531812）， respectively， and the number of pSc250-family hybridization signals were 17 and 24 in Psa. juncea and L. secalinus， respectively， but no signal was detected in two L. racemosus samples. The distribution of retrotransposon sequences on the chromosomes of three detected species was basically dispersed， and the distribution of chromosome sequences in Leymus species showed a tendency of homogenity. Especially， clone sequences pPj-44 and pPj-28 showed significant differences in signal distribution between Psa. juncea and Leymus species， suggesting sequence expansion and contraction， respectively， during allopolyploidization， and clone sequence pPj-77 only differentiated the hybridization intensity of 10 chromosomes from the rest of the chromosomes in one L. racemosus（PI 531812）. The results suggested the repeats of Psa. juncea evolved rapidly and had homogenous diffusion during the polypoid formation of Leymus species and the repeat composition might be significant different among different Leymus species.

In order to explore the ploidy level and genome size of Sorbus sect. Sorbus species， the nuclear DNA content from somatic cells was measured by flow cytometry and Oryza sativa subsp. japonica ‘Nipponbare’ was used as the internal control. The results showed that the genome size of 19 species ranged from 0.648 to 0.803 pg， with the diploid， triploid and tetraploid levels， including 15 diploid species with 2C values ranging from 1.335 to 1.607 pg for， and one triploid species S. himalaica with 2C values of 2.137 pg，and three tetraploid species， S. albopilosa， S. prattii and S. pseudovilmorinii， with 2C values of 2.594， 2.891 and 2.751 pg， respectively. The 2C values of 16 species and new ploidy levels of five species were reported for the first time， indicating that there were changes of ploidy heterogeneity among interspecific and intraspecific in Sorbus sect. Sorbus.

The expression of gene transcription activation based on CRISPR-dCas9 might avoid phenotypic interference caused by gene ectopic expression， and made genes expressed efficiently and specifically. In this study， a novel CRISPR-Act3.0 expression system based on CRISPR-dCas9 was used to perform transcriptional activation of the vascular cambium-specific transcription factor ANT（AINTEGUMENTA） in Populus trichocarpa to create genetic materials and function analysis. First， homology analysis was conducted on the PtrANTs transcription factors of P. trichocarpa， and PtrANT-4 was selected for subsequent research. PtrANT-4 gene was cloned and its expression in various tissues was analyzed using fluorescence quantitative PCR. Secondly， three gRNAs were designed on the gene promoter of PtrANT-4， and the transcriptional activation expression vector CRISPR-dCas9/ANTprogRNAs was constructed. The expression of the vector was detected by transient protoplast transformation method. Finally， the expression vector was transformed into P. trichocarpa using Agrobacterium-mediated method， and transcription-activated genetic plants of PtrANT-4 were obtained. The results showed that there were four PtrANTs transcription factors in P. trichocarpa. PtrANT-4 was specifically expressed in vascular cambium of lateral meristem of P. trichocarpa. The transcription activation vector successfully constructed based on the CRISPR-Act3.0 expression system has the transcriptional activation effect of PtrANT-4 after transformation in xylem protoplasts of P. trichocarpa. The expression level of the PtrANT-4 gene in the genetically transformed plants was significantly increased only in the vascular cambium， suggesting that PtrANT-4 might play an important role in the development of stem vascular cambium This study lays a foundation for the functional study of PtrANT， and provides important genetic materials for the study of the mechanism of vascular cambial stem cell development.

To explore the metabolic response mechanism of Lagerstroemia indica ‘Pink Velour’ to salt and alkali stresses， one-year-old asexual cottage seedlings were treated to salt stress（NaCl， pH=7.02） and alkali stress（NaHCO₃ and Na₂CO₃， Na⁺ mole ratio 2∶1， pH=9.52） respectively， and the leaves metabolic changes and differences of the two treatment groups and the control group（CK） were analyzed and compared by using liquid chromatography mass spectrometry（LC-MS）. The results showed that 156 and 176 different metabolites were screened in salt and alkali stress group respectively， and 23 different metabolites were screened in both groups， and the rest were unique different metabolites. KEGG enrichment analysis showed that the biosynthesis of secondary metabolites， amino acid metabolism， carbohydrate metabolism， fatty acid metabolism and plant hormone synthesis were main metabolic pathways in response to salt and alkali stress. Glycine， serine and threonine anabolism， ABC transporter protein and Vitamin B₆ anabolism were the unique metabolic pathways in salt stress groups. Biosynthesis of valine， leucine， isoleucine， arginine， proline， folic acid and ascorbic acid， and mutual transformation between pentose and glucuronic were the unique metabolic pathway in alkali stress groups. The changes of different metabolites and enriched metabolic pathways might be the main mechanism of L. indica response to the salt stress and alkali stress.

FERONIA （FER） receptor kinase plays an important role in pollen and stigma recognition in flowering plants. To analyze the function of receptor-like kinase FERONIA（FER） in the pollination in ornamental kale（Brassica oleracea var. acephala）， BoFER gene was cloned from the stigma of the self-incompatibility line（S_13-bS_13-b ） of ornamental kale by RT-PCR， and the cloned cDNA sequence was 2 682 bp， which encoded 893 amino acids containing the highly conserved kinase domain and Ser/Thr kinase binding site， and the expression level of BoFER was analyzed by qRT-PCR. The results showed that the expression of BoFER in stigmas gradually increased after incompatible pollination， but gradually decreased after compatible pollination. Furthermore， the interaction between BoFER and known proteins related to self-incompatibility were analyzed by yeast two-hybrid. The results suggested that BoFER interacted with the kinase domain of S-locus receptor kinase BoSRK_13-b.

To analyze gene function in plants lacking stable genetic transformation system， virus-induced gene silencing（VIGS） was needed， and Iris sanguinea， a monocotyledon， was selected as materials. The specific fragment of IsPDS gene was isolated and the VIGS recombinant vector pTRV2-IsPDS was constructed and leaves were infected by injection. The results showed that the most effective infection was achieved by injecting its leaf veins with syringes when the OD₆₀₀ values of the resuspension were adjusted to 0.8-1.0 after the those of pTRV1 and pTRV2-IsPDS were adjusted to 1.8-2.0. The experiment was conducted when outdoors temperature was 15-20 ℃ from 6 p.m. to 8 p.m.， and a 1 mL syringe needle pricking the outer epidermis of I. sanguinea leaves and 1 mL of heavy suspension slowly injected along parallel veins into its vascular bundles. A clear albino phenotype might appear after about 14 days. TRV1 and TRV2 virus vectors were detected in the plants with phenotypic changes and in the no-load group. The expression of IsPDS in the albino plants was significantly lower than that in the no-load group and the control group. With the concentration of agrobacterium tumefaciens carrying virus vector increased in the preparation of infection solution， the infection efficiency of the whole experiment was improved， and no shading was needed after inoculation.

To provide theoretical basis for genetic improvement of reproductive regulatory traits of Catalpa bungei， DELLAs family genes were identified and the function of CbuGRAS9 was analyzed. Based on the genomic data of Catalpa bungei， five CbuDELLAs genes homologous to Arabidopsis thaliana were identified and cloned. ExPASy， SWISS-MODEL， Plant-mPloc， PlantCare and other online tools were used to predict the isoelectric point， protein structure， sub-cellular localization and promoter cis-acting elements of CbuDELLAs protein. The expression differences of CbuDELLAs were analyzed by using Catalpa ‘Bairihua’ and Catalpa bungei ‘Luoqiu No.1’ as materials， and the molecular function of CbuGRAS9 was confirmed by heterologus transformation in Arabidopsis thaliana， and the proteins interacted with CbuGRAS9 were screened by yeast two-hybrid library. The results showed that the amino acid number of the five CbuDELLAs proteins ranged from 455 to 588 aa， the relative molecular weight of the proteins ranged from 5.04 to 6.43 kDa， and the isoelectric point value ranged from 4.81 to 5.14. All CbuDELLAs proteins contained DELLA and GRAS conserved domains and are hydrophilic proteins. Sub-cellular localization prediction showed that CbuDELLAs protein was located in the nucleus. The analysis of promoter cis-acting elements showed that the five promoter regions of DELLAs all contained cis-acting elements involved in gibberellin reaction. The results of qRT-PCR showed that the expression of CbuDELLAs in Catalpa ‘Bairihua’ were significantly higher than that in Catalpa bungei ‘Luoqiu No.1’， and CbuGRAS9 was the most significantly gene， and the flowering time of CbuGRAS9 transgenic plants were significantly delayed. Proteins interacted with CbuGRAS9 were mainly concentrated in metabolic pathways such as ribosome， amino acid synthesis， secondary metabolism， photosynthesis and TCA cycle.

In order to investigate the function of HMG（High mobility group proteins） genes under abiotic stresses in Populus davidiana×P. bolleana， the HMG genes were cloned and the stress tolerant function of HMGs was identified， and the theoretical foundation for using the gene in tree breeding through genetic engineering was laid. Seven homologous genes of ArabidopsisHMGs（named PdbHMG1-7） were found by homologous sequence alignment， and sequence analysis of PdbHMG1-7 was performed using bioinformatics tools respectively， the expression patterns of PdbHMG1-7 gene in leaves and roots of Populus davidiana×P.bolleana under different stresses were investigated by qRT-PCR.Results The ORF length of PdbHMG1-7 were 456-2 004 bp respectively， the amino acid residues encoded by PdbHMG1-7 genes were 151-667 aa， and the molecular weight of the encoded protein were 16.72-75.54 kDa， and the theoretical isoelectric point were 5.35-9.36， and the seven PdbHMG were hydrophilic proteins. The results of multiple sequence alignment and phylogenetic tree analysis showed that all 7 PdbHMG genes contained HMG-box conserved domains and belonged to HMGB subfamily. The analysis results of cis-acting elements contained in the promoter showed that the promoter sequence of PdbHMG genes contained a variety of elements in response to hormones and stress. The expression pattern analysis showed that the expression levels of seven PdbHMGs in roots and leaves under NaCl， PEG₆₀₀₀， ABA and CdCl₂ stress treatment changed in at least one stress treatment time point respectively. In leaves， PdbHMG2 were induced under the stress of NaCl， PEG₆₀₀₀， ABA and CdCl₂， and almost all of them were significantly up-regulated respectively， but PdbHMG7 was down-regulated. Under NaCl and CdCl₂ stress， PdbHMG1， PdbHMG3 and PdbHMG6 were almost significantly up-regulated during the whole stress process respectively. The expressions of PdbHMG3 in leaves were also significantly up-regulated at most time points under NaCl and CdCl₂ stress. In roots， the expression of PdbHMG3 and PdbHMG5 was significantly up-regulated in the whole process of NaCl treatment. However， PdbHMG6 was not significantly expressed during NaCl stress except for 9-12 h， the expression of PdbHMG6 was significantly down-regulated at other stress time points. During ABA treatment， PdbHMG6 was down-regulated in roots. Conclusion The results showed that seven PdbHMG genes could respond to at least one stress treatment in one organ， but the types and mechanisms of involved stress response might be different. This study provided a reference for further studying the function of PdbHMGs family genes in Populus davidiana×P. bolleana.

To explore the relationship between the Catalase（CAT） gene and saline-alkali stress tolerance of Lilium pumilum， the CAT gene was successfully cloned from L. pumilum bulb. The length of region ORF was 1 479 bp， encoding 492 amino acids， and sequence alignment and phylogenetic tree analysis were performed， and the Catalase protein of L. pumilum was found to be closely related to the Catalase proteins of L. sargentiae， Ananas comosus， Elaeis guineensis and other plants. The Catalase protein was induced to express， and purified in vitro with 1 mol·L^-1 IPTG as the inducer after constructing prokaryotic expression vector pQE-LpCat. The results showed that the growth concentration of bacteria solution containing PQE-LpCat protein was higher than that of the control strain under the stress of 50 mmol·L^-1 NaHCO₃. Under the stress of 1 mol·L^-1 NaHCO₃ and 2.5 mol·L^-1 H₂O₂， less wilting was observed in plants overexpressing the LpCAT gene compared to wild-type. Determination of the physiological indexes including net photosynthetic rate， stomatal conductance， intercellular CO₂ and transpiration rate， H₂O₂ concentration and contents of malondialdehyde（MDA） showed that tobacco plants overexpressing the LpCat gene were more tolerant to saline and alkali stress than wild-type tobacco plants.

To clarify the function of FmCCoAOMT gene， the expression pattern of FmCCoAOMT gene was analyzed by qRT-PCR using Fraxinus mandshurica as material in this study. The results showed that FmCCoAOMT gene was tissue specific. The expression level was the highest in the xylem of both female and male perennial plants， and was 9.4 times higher than that in the bark of new shoots in male plants， and was 13.1 times higher than that of leaf in female plants. The leaf disk method was used to obtain transgenic tobacco plants. Compared with the wild type， the lignin content of overexpressing FmCCoAOMT was increased by 41%， while the cellulose and hemicellulose contents were decreased by 32% and 52%， respectively. Tobacco overexpressing FmCCoAOMT after abiotic stress treatment compared to wild type， the activity of POD and SOD increased， the content of MDA decreased， and the content of reactive oxygen decreased after stress treatment. After NaCl treatment， POD activity was 83% higher than that of control group. After NaCl， ABA and mannitol treatments， SOD activity increased by 56.6%， 44.2% and 19.0%， and MDA content decreased by 77.2%， 11.7% and 47.6%， respectively. The results indicated that FmCCoAOMT gene might be involved in lignin synthesis of F. mandshurica， promoted abiotic stress tolerance.

To investigate the effect of β-amyrin synthase gene（Aeβ-AS） on triterpenoid saponin synthesis of Aralia elata， the Aeβ-AS gene was cloned and genetically transformed into tobacco. The expression difference of Aeβ-AS gene in different parts of transgenic tobacco was analyzed， and the expression levels of Aeβ-AS gene， upstream and downstream key enzyme genes and total triterpene content were detected respectively. The results showed that the plant overexpression vector PROKⅡ-Aeβ-AS was successfully constructed and transferred into wild type tobacco， and seven transgenic lines were obtained and expressed at the mRNA level， and the expression level in leaves was higher than that in roots and stems. In transgenic tobacco， the expression levels of Aeβ-AS gene and its upstream and downstream key enzyme genes were higher than those of wild type， and the relative expression levels of NtFPS and NtSS genes of strain L21 were the highest， and the relative expression levels of NtSE and Aeβ-AS genes of strain L30 were the highest. Compared with wild-type tobacco， the total triterpene content of GM tobacco was significantly increased（1.1-1.6 times）. The results showed that synthesis of Aeβ-AS gene and heterologous transformation in tobacco could significantly increase the total triterpene content in transgenic tobacco.

In order to explore the role of WALLS ARE THIN（WAT1） in wood formation and response to stress in woody plants， bioinformatics toolswas used for analysis， and quantitative Real-time PCR（qRT-PCR） was used to investigate the expression patterns of EgrWAT1L and EgrWAT1S in different tissues， internodes and in response to different stresses， and the gene EgrWAT1S and its other transcript EgrWAT1L were cloned from Eucalyptus grandis. The results showed that the EgrWAT1S was highly expressed in phloem， while EgrWAT1L was mainly expressed in roots， and the expression patterns were significantly different under methyl jasmonate（MeJA） and salicylic acid（SA） treatment， salt stress， phosphorus（P） and boron（B） deficiency， and even opposite under MeJA and SA. These results suggested that EgrWAT1L might affect EgrWAT1S expression through transcriptional regulation and further protein translation in response to hormone and stress treatments. The studies provided a basis for further elucidate the function in the growth and development of EgrWAT1 gene and also provided a possibility for future molecular breeding of Eucalyptus.

To investigate the role of WRKY transcription factors（TFs） in sensing saline-alkali stress signals and maintaining their tolerance function through physiological and biochemical regulatory pathways， and the WRKY42 gene of Amorpha fruticosa was cloned and the expression pattern in response to salt（NaCl） and alkali（NaHCO₃） stress and tissue organs was analyzed， and the salinity tolerance function was also studied its by overexpression in tobacco. In this study， the AfWRKY42 gene was cloned based on transcriptome sequencing data of A. fruticosa L. under stress. Bioinformatics analysis showed that AfWRKY42 contained a WRKY structural domain， two low-complexity regions and a helix region. Phylogenetic tree analysis of amino acids revealed that AfWRKY42 was most closely related to WRKY47 of Cajanus cajan and WRKY42 of Mucuna pruriens. The localization of AfWRKY42 protein in mesophyll protoplasts of Arabidopsis thaliana was confirmed in nucleus by a transient gene expression system. Quantitative analysis of AfWRKY42 gene showed the highest expression in the shoot epidermis of Sophora japonica. Detection of expression patterns in roots and leaves treated with NaCl and NaHCO₃ showed an overall increasing trend induced by it， suggesting that overall stress induced an increase in AfWRKY42 gene expression， and AfWRKY42 gene was associated with the regulation of salinity tolerance in plants. Analysis of salinity tolerance in 35S-initiated overexpressing T3 generation of tobacco lines transgenic for AfWRKY42 gene showed that the transgenic tobacco lines showed increased resistance after salinity stress treatment， it had higher chlorophyll and electrical conductivity and significantly lower malondialdehyde content than the wild type， indicating that AfWRKY42 played an important regulatory role in response to salinity stress. It would provide a WRKY transcription factor candidate gene for salinity resistance breeding and lay the foundation for improving the resistance of A. fruticosa and other plants.

To investigate the potential function of ubiquitin carboxyl terminal hydrolases（UCHs） in the ubiquitination process of laticiferous of Hevea brasiliensis， the full-length sequences of two UCHs family members（HbUCH-L3 and HbUCH-L5） were isolated from Hevea brasiliensis， and both had typical UCHs domains. The open reading frame of HbUCH-L3 and HbUCH-L5 were 993 bp and 558 bp， and encoded 330 and 185 amino acids， respectively. The results of qRT-PCR showed that HbUCH-L3 and HbUCH-L5 were constitutively expressed in all tissues， but was low in latex. In vitro ubiquitination substrates cleavage of recombinant HbUCHs showed that both HbUCH-L3 and HbUCH-L5 had the function of hydrolyzing ubiquitin. HbUCHs significantly reduced the overall ubiquitination level of C-serum proteins； while， the deubiquitinating activity of HbUCH-L3 was higher than that of HbUCH-L5. Therefore， it was speculated that UCHs played a role in maintaining the dynamic balance of laticiferous ubiquitination and thus played a specific biological function， but the exact mechanism was still unclear.

In order to cultivate rice varieties resistant to Xanthomonas oryzae pv. oryzae， Rhizoctonia solani， Magnaporthe oryzae and Fusarium fujikuroi， the method of mining resistance genes is an important way to select resistant varieties. RT-PCR method was used to clone the LcWRKY40 gene （MN187915） from the leaves of Leymus chinensis. The result showed that the CDS was 1 053 bp in length and encoded 350 amino acids with a molecular weight of 38.1 kDa. The results of bioinformatics analysis showed that the primary structure of LcWRKY40 contained WRKY domain， zinc finger protein domain and nuclear localization sequence. Phylogenetic tree construction and motif analysis showed that the phylogenetic relationship between LcWRKY40 and HvWRKY38 was closed. The results of subcellular localization in tobacco showed that the LcWRKY40 protein was located in the nucleus， verified by the software prediction. qRT-PCR tissue specific expression analysis showed that LcWRKY40 gene was expressed in root， stem， leaf， leaf sheath， Lemma and anther of Leymus chinensis respectively， but the expression level was the highest in leaf but the lowest in Lemma. Transgenic LcWRKY40 tobacco plants and wild-type tobacco plants were inoculated with X. oryzae pv. Oryzae， R. solani， M. oryzae and F. fujikuroi， respectively， which showed that transgenic LcWRKY40 tobacco plants could alleviate the four pathogens in different degrees， and showed high resistance to M. oryzae and F. fujikuroi. Therefore， it was speculated that LcWRKY40 protein played a key regulatory role in signal pathways such as resisting disease stress and improved the resistance of plant pathogens， which layed a molecular foundation for the study of LcWRKY40 function and abiotic stress.

To explore the role of SSR1 gene encoding a functionally unknown mitochondrial protein of Arabidopsis thaliana in plant growth and stress response， ssr1-2 and its suppressor mutants EMS143 and EMS145 were used to track the growth of their roots and aboveground parts， as well as their proline sensitivity and iron homeostasis， and the effects of ssr1-2 short root phenotype on aboveground growth of seedlings were analyzed by micrografting. The results showed that the primary root length of ssr1-2 was shorter and the root architecture was similar to the fibrous root system. The growth of their shoots was also retarded， but appeared considerably later than the short-root phenotype. The results of micrografting revealed that the roots of ssr1-2 could restrict the growth of the wild-type shoots and， and conversely， the shoot of ssr1-2 could also affect the growth of the wild-type roots， but the former had a bigger effect. ssr1-2 showed a hypersensitive phenotype to proline in seed germination， root length and leaf chlorophyll content. In addition， ssr1-2 appeared insensitive to Fe nutrition， that was， the stimulating effect of Fe salt on seedling growth was significantly less than that of wild-type WS， indicating a significant decrease in its ability to utilize Fe. The results suggested that SSR1 might be involved in the regulation of A. thaliana root growth by affecting the utilization of iron nutrient， implying that the impairment of the mitochondrial iron utilization machinery might contribute significantly to the enhanced inhibitory effect of proline on plant growth and development.