Identification of new cotton fiber-quality QTL by multiple genomic analyses and development of markers for genomic breeding

Cotton fiber is one of the main raw materials for the textile industry.In recent years,many cotton fiber quality QTL have been identified,but few were applied in breeding.In this study,a genome wide association study(GWAS)of fiber-quality traits in 265 upland cotton breeding intermediate lines(GhBreeding),combined with genome-wide selective sweep analysis(GSSA)and genomic selection(GS),revealed 25 QTL.Most of these QTL were ignored by only using GWAS.The CRISPR/Cas9 mutants of GhMYB_D13 had shorter fiber,which indicates the credibility of QTL to a certain extent.Then these QTL were verified in other cotton natural populations,5 stable QTL were found having broad potential for application in breeding.Additionally,among these 5 stable QTL,superior genotypes of 4 showed an enrichment in most improved new varieties widely cultivated currently.These findings provide insights for how to identify more QTL through combined multiple genomic analysis to apply in breeding.

Red fluorescent protein (DsRed2), an ideal reporter for cotton genetic transformation and molecular breeding

Genes encoding reporter proteins are used as visual marker-assisted tools in genetic transformation as well as plant breeding. In this study, the red fluorescent protein identified in Discosoma sp. coral(DsRed2) was successfully used as a visual marker for cotton genetic engineering. DsRed2 was successfully expressed in two cotton cultivars,JIN668 and YZ1, driven by the Ca MV-35 S promoter via the Agrobacterium-mediated transformation. Our results suggest that DsRed2 expression provides an early-stage selection tool for the transgenic calli via visual observation. Red fluorescence can be detected not only in callus and somatic embryos but also in most tissues and organs of mature plants. The transgenic line Yz-2-DsRed2 was crossed with four different cotton cultivars to assess the transgene heritability and stability in different genetic backgrounds.The heritability of the red color was highly stable when Yz-2-DsRed2 was used as a male parent. The DsRed2 gene expressed 100% in the F_1 hybrids. To investigate the relationship between DsRed2 transcription and DNA methylation, a methylation-specific PCR approach was applied to the Ca MV-35 S promoter region. The results showed a negative association between DNA methylation level in the promoter region and the transgene transcription.Taken together, these findings suggest DsRed2 a visual reporter gene for cotton genetic transformation and molecular breeding programs.

High-temperature stress suppresses allene oxide cyclase 2 and causes male sterility in cotton by disrupting jasmonic acid signaling

Cotton(Gossypium spp.) yield is reduced by stress. In this study, high temperature(HT) suppressed the expression of the jasmonic acid(JA) biosynthesis gene allene oxide cyclase 2(GhAOC2), reducing JA content and causing male sterility in the cotton HT-sensitive line H05. Anther sterility was reversed by exogenous application of methyl jasmonate(MeJA) to early buds. To elucidate the role of GhAOC2 in JA biosynthesis and identify its putative contribution to the anther response to HT, we created gene knockout cotton plants using the CRISPR/Cas9 system. Ghaoc2 mutant lines showed male-sterile flowers with reduced JA content in the anthers at the tetrad stage(TS), tapetum degradation stage(TDS), and anther dehiscence stage(ADS). Exogenous application of MeJA to early mutant buds(containing TS or TDS anthers) rescued the sterile pollen and indehiscent anther phenotypes, while ROS signals were reduced in ADS anthers. We propose that HT downregulates the expression of GhAOC2 in anthers, reducing JA biosynthesis and causing excessive ROS accumulation in anthers, leading to male sterility. These findings suggest exogenous JA application as a strategy for increasing male fertility in cotton under HT.

Repression of microRNA 160 results in retarded seed integument growth and smaller final seed size in cotton

microRNA 160(miR160),targeting auxin response factors(ARFs),plays many roles in plant development.We investigated the role of the mi R160/ARF axis in regulation of cotton seed size.Suppressing mi R160 activity,specifically in the seed coat,led to smaller seeds and less fiber production owing to attenuated growth of the maternal integument.Scanning electron microscopy and histology showed that expansion of cells in the integument was retarded in mi R160-suppressed lines.Four Gh ARF genes were targeted by mi R160 and were upregulated in mi R160-suppressed lines,indicating that a mi R160/ARF axis is present in cotton.Five genes(Ghir_A05 G003740,Scaffold1878 G000010,Ghir_D09 G024980,Ghir_A11 G010730,and Ghir_A05 G041590),associated with reduced seed development were downregulated in mi R160-suppressed lines.Our results suggest that the mi R160/ARF axis controls maternal integument growth to influence seed size by directly or indirectly regulating seed development-associated genes.

The laccase gene Gh Lac1 modulates fiber initiation and elongation by coordinating jasmonic acid and flavonoid metabolism

Cotton fibers are single cells originating in the epidermis of cotton ovules,and serve as the largest natural fiber source for the textile industry.In theory,all epidermal cells have the potential to develop into fibers,but only 15%–25%of epidermis cells develop into commercially viable lint fibers.We previously showed that Gh Lac1 participates in cotton defense against biotic stress.Here we report that Gh Lac1 also has a role in cotton fiber development.Gh Lac1 RNAi lines in cotton showed increased differentiation of fiber initials from epidermis and shortened fiber length,resulting in unchanged lint percentage.Suppression of Gh Lac1 expression led to constitutively hyperaccumulated jasmonic acid(JA)and flavonoids in ovules and fiber cells.In vitro ovule culture experiments confirmed the distinct roles of JA and flavonoids in fiber initiation and elongation,and showed that fiber development is spatially regulated by these chemicals:the increased fiber initiation in Gh Lac1 RNAi lines is caused by hyperaccumulated JA and rutin content during the fiber initiation stage and shortened fiber length is caused by constitutively increased JA and naringenin content during the fiber elongation stage.

Phenotypic plasticity and genetic variation of cotton yield and its related traits under water-limited conditions

Global warming is limiting availability of water resources in arid and semi-arid regions,and so understanding water use efficiency(WUE)is increasingly important for agricultural production in those areas.As China is the largest cotton producing area,the problem of balancing WUE and efficient cotton production is a major issue.In this study,we used a natural population of 517 Upland cotton accessions to conduct a water-controlled trial in south and north of Xinjiang over two years.A total of 18 traits including agronomic traits,fiber yield indices and fiber quality indices,were investigated for broad-sense heritability and coefficient of variation.Appropriate water limitation was found to promote the establishment of favorable agronomic traits in cotton,associated with an increased cotton yield of 8.46%in Xinjiang,at the expense of a certain degree of fiber quality,such as decreased fiber length and an over-higher micronaire value.We detected 33 QTL related to response to water limitation using a drought resistance coefficient(DRC),and 6 QTL were found using a comprehensive indicator of CIDT(comprehensive index of drought tolerance)at the genetic level by integrating resequencing data.Two novel QTL-hotspots including six differentially expressed genes(DEGs)were further identified related to the drought response of cotton.These findings not only suggested a new approach to irrigation of cotton fields in Xinjiang,but also provided abundant genetic evidence for genetic breeders to study drought improvement of crops.

Transcriptome and metabolome analysis reveal that oral secretions from Helicoverpa armigera and Spodoptera litura influence wound-induced host response in cotton

Cotton(Gossypium hirsutum)is an important fiber crop worldwide.Insect attack causes cotton yield and quality losses.However,little is known about the mechanism of cotton response to insect attack.We simulated insect feeding by applying insect oral secretions(OS)to wounds,and combined transcriptome and metabolome analysis to investigate how OS from two major pest species(Helicoverpa armigera and Spodoptera litura)affect cotton defense responses.We found that respectively 12,668 and 13,379 genes were differentially expressed in comparison with wounding alone.On addition of OS,the jasmonic acid signaling pathway was rapidly and strongly induced,whereas genes involved in salicylic acid biosynthesis were downregulated.On constructing a coexpression gene network,we identified a hub gene encoding a leucine-rich repeat receptor kinase that may play an important role in early signal recognition and transduction.OS from the two insect species altered the abundance of flavonoid-related compounds in different patterns.Gossypol remained in lower concentration after OS application than after wounding alone,suggesting a suppressive effect of OS on cotton defense response.This study illustrated transcriptional and metabolic changes of cotton in responding to OS from two chewing insect species,identified potential key response genes,and revealed evidence for OS inhibition of wounding-induced cotton defense response.

Attenuation of ethylene signaling increases cotton resistance to a defoliating strain of Verticillium dahliae

The severity of Verticillium wilt on cotton caused by defoliating strains of Verticillium dahliae has gradually increased and threatens production worldwide. Identification of the molecular components of leaf defoliation may increase cotton tolerance to V. dahliae. Ethylene, a major player in plant physiological processes, is often associated with senescence and defoliation of plants. We investigated the cotton–V.dahliae interaction with a focus on the role of ethylene in defoliation and defense against V. dahliae.Cotton plants inoculated with V. dahliae isolate V991, a defoliating strain, accumulated more ethylene and showed increased disease symptoms than those inoculated with a non-defoliating strain. In cotton with a transiently silenced ethylene synthesis gene(GhACOs) and signaling gene(GhEINs) during cotton–V. dahliae interaction, ethylene produced was derived from cotton and more ethylene increased cotton susceptibility and defoliation rate. Overexpression of AtCTR1, a negative regulator in ethylene signaling, in cotton reduced sensitivity to ethylene and increased plant resistance to V. dahliae.Collectively, the results indicated precise regulation of ethylene synthesis or signaling pathways improve cotton resistant to Verticillium wilt.

miR398b negatively regulates cotton immune responses to Verticillium dahliae via multiple targets

MicroRNAs(miRNAs)play essential roles in plant defense responses,although such roles have not been identified in cotton in response to the plant pathogenic fungus Verticillium dahliae.In this study,the functions of miR398b and its target genes in cotton-V.dahliae interaction were investigated.The transcript levels of miR398b were down-regulated by V.dahliae infection and miR398b overexpression in cotton made the plants more susceptible to V.dahliae.The results suggest that miR398b negatively regulates cotton resistance to V.dahliae.This may occur by miR398b repression of some CC-NBS-LRR genes via translational inhibition,interfering with defense responses and leading to cotton susceptibility to V.dahliae.Alternatively,miR398b may guide the cleavage of the mRNAs of GhCSD1,GhCSD2 and GhCCS,each of which functions in reactive oxygen species(ROS)regulation and homeostasis,thereby causing excessive ROS accumulation in miR398b-overexpressing plants in response to V.dahliae infection.This study suggests conserved and novel roles of miR398b in the cotton–V.dahliae interaction.These discoveries may be coupled with new strategies in cotton breeding programs to improve resistance to V.dahliae.

Vickers hardness change of the Chinese low-activation ferritic/martensitic steel CLF-1 irradiated with high-energy heavy ions

In the present work,the irradiation hardening behavior of a Chinese low-activation ferritic/martensitic steel CLF-1,a candidate for fusion reactor blankets,is studied.Specimens were irradiated with high-energy14N and56Fe ions at the terminal of a cyclotron to three successively increasing damage levels of 0.05,0.1 and 0.2 displacements per atom(dpa)at about-50°C.The energy of the incident ions was dispersed to 11 successively decreasing grades using an energy degrader,thereby generating an atomic displacement damage plateau in the specimens from the surface to a depth of 25μm,which is sufficiently broad for the Vickers hardness test.Eight different loads(i.e.98 mN,196 m N,490 m N,980 m N,1.96 N,4.9 N,9.8 N and 19.6 N)were applied to the specimens to obtain the depth profiles of the Vickers hardness by using a microhardness tester.Hardening was observable at the lowest damage level,and increased with increasing irradiation dose.A power-law correlation of the Vickers hardness with the damage level(HV0=1.49+0.76 dpa0.31)is proposed.Testing with a nano-indentation technique was also performed,and a linear relationship between the Vickers micro-hardness and the nanohardness(HV0=0.83 H0)was observed.A comparison with other RAFM steels(CLAM,JLF-1,F82 H,EUROFER97 etc.)under neutron or charged particle irradiation conditions shows that most of the RAFM steels exhibit similar power-law exponents in the dose dependence of irradiation hardening.The difference in the irradiation hardening may be attributed to differences in microstructure prior to irradiation.

Comparative genomic analyses reveal cis-regulatory divergence after polyploidization in cotton

Polyploidization has long been recognized as a driver for the evolutionary formation of superior plant traits coupled with gene expression novelty.However,knowledge of the effect of regulatory variation on expression changes following polyploidization remains limited.In this study,we characterized transcriptional regulatory divergence by comparing tetraploid cotton with its putative diploid ancestors.We identified 144,827,99,609,and 219,379 Tn5 transposase-hypersensitive sites(THSs)in Gossypium arboreum,G.raimondii,and G.hirsutum,respectively,and found that the conservation of promoter THSs was associated with coordination of orthologous genes expression.This observation was consistent with analysis of transcription-factor binding sites(TFBS)for 262 known motifs:genes with higher TFBS conservation scores(CS)showed less change than those genes with lower TFBS CS in expression levels.TFBS influenced by genomic variation were involved in the novel regulation networks between transcriptional factors and target genes in tetraploid cotton.We describe an example showing that the turnover of TFBS was linked to expression pattern divergence of genes involved in fiber development(fiber-related genes).Our findings reveal the regulatory divergence of the transcriptional network in cotton after polyploidization and characterizes the regulatory relationships of genes contributing to desirable traits.

Study on Co-Effect of K₂SO₄Deposition and Low Concentration SO₂on Performances of V₂O₅/AC Catalysts for Low Temperature SCR

Simulated compounds were prepared by loading K2SO4 onto V2O5/AC catalysts. Study the effect of K2SO4 on V1/AC catalysts in the presence of low concentration SO2. Transient response techniques, TPD was carried out. The results indicated that the DeNO activity of V1/AC catalysts was decreased seriously in the early period of operation, but the deactivation was gradually diminished with SO2 adsorption and then, it was completely eliminated. For the sulphated catalysts (saturated catalysts by sulphate), their SCR activity were free from existence of gaseous SO2. the loss of activity about 10% caused by K2SO4 was found on them. The deactivation of K2SO4 deposited catalysts was due to the decrease of adsorbed and activated NH3, or some acid sites.

棉属光敏色素PHY基因家族的全基因组鉴定与驯化选择分析

光敏色素(PHY)作为植物体内重要的红光(R)和远红光(FR)受体,在调节植物花期、提高作物产量以及调控植物抗逆性方面均具有重要作用。鉴定棉花PHY基因,探究其驯化和改良的遗传调控网络,发掘棉花光敏色素关键基因,为早熟棉花品种的从头驯化和育种提供新见解。以5个拟南芥(Arabidopsis thaliana)光敏色素基因作为种子序列,利用生物信息学方法,对不同棉种中的PHY基因进行全基因组系统鉴定。系统发育分析表明,锦葵科植物中的PHY基因包括PHYA、PHYB、PHYC与PHYE四个亚家族。PHY基因在陆地棉(Gossypium hirsutum)不同群体间的驯化选择分析结果表明, PHY基因的驯化过程可分为早期驯化和后期遗传改良2个阶段。对陆地棉野生种和栽培品种在长、短日照下的转录组分析显示,GhPHYA1Dt和GhPHYB1Dt在长、短日照下的表达差异显著;在长日照处理14小时后,栽培品种GhPHYC1At和GHPHYE1At的表达量显著低于野生种。研究结果为进一步揭示棉花PHY基因的驯化选择和功能机制奠定了基础,为棉花早熟新品种选育和从头驯化提供了理论依据。

High-quality Gossypium hirsutum and Gossypium barbadense genome assemblies reveal the landscape and evolution of centromeres

Centromere positioning and organization are crucial for genome evolution;however,research on centro-mere biology is largely influenced by the quality of available genome assemblies.Here,we combined Oxford Nanopore and Pacific Biosciences technologies to de novo assemble two high-quality reference genomes for Gossypium hirsutum(TM-1)and Gossypium barbadense(3-79).Compared with previously published reference genomes,our assemblies show substantial improvements,with the contig N50 improved by 4.6-fold and 5.6-fold,respectively,and thus represent the most complete cotton genomes to date.These high-quality reference genomes enable us to characterize 14 and 5 complete centromeric regions for G.hirsutum and G.barbadense,respectively.Our data revealed that the centromeres of allotetraploid cotton are occupied by members of the centromeric repeat for maize(CRM)and Tekay long terminal repeat families,and the CRM family reshapes the centromere structure of the At subgenome after polyploidization.These two intertwined families have driven the convergent evolution of centromeres between the two subgenomes,ensuring centromere function and genome stability.In addition,the reposi-tioning and high sequence divergence of centromeres between G.hirsutum and G.barbadense have contributed to speciation and centromere diversity.This study sheds light on centromere evolution in a sig-nificant crop and provides an alternative approach for exploring the evolution of polyploid plants.

CRISPR-Cas9-mediated construction of a cotton CDPK mutant library for identification of insect-resistance genes

Calcium-dependent protein kinases(CDPKs)act as key signal transduction enzymes in plants,especially in response to diverse stresses,including herbivory.In this study,a comprehensive analysis of the CDPK gene family in upland cotton revealed that GhCPKs are widely expressed in multiple cotton tissues and respond positively to various biotic and abiotic stresses.We developed a strategy for screening insect-resistance genes from a CRISPR-Cas9 mutant library of GhCPKs.The library was created using 246 single-guide RNAs targeting the GhCPK gene family to generate 518 independent T0 plants.The average target-gene coverage was 86.18%,the genome editing rate was 89.49%,and the editing heritability was 82%.An insect bioassay in the field led to identification of 14 GhCPK mutants that are resistant or susceptible to insects.The mutant that showed the clearest insect resistance,cpk33/74(in which the homologous genes GhCPK33 and GhCPK74 were knocked out),was selected for further study.Oral secretions from Spodoptera litura induced a rapid influx of Ca^(2+) in cpk33/74 leaves,resulting in a significant increase in jasmonic acid content.S-adenosylmethionine synthase is an important protein involved in plant stress response,and protein interaction experiments provided evidence for interactions of GhCPK33 and GhCPK74 with GhSAMS1 and GhSAM2.In addition,virus-induced gene silencing of GhSAMS1 and GhSAM2 in cotton impaired defense against S.litura.This study demonstrates an effective strategy for constructing a mutant library of a gene family in a polyploid plant species and offers valuable insights into the role of CDPKs in the interaction between plants and herbivorous insects.

A comprehensive overview of cotton genomics,biotechnology and molecular biological studies

Cotton is an irreplaceable economic crop currently domesticated in the human world for its extremely elongated fiber cells specialized in seed epidermis,which makes it of high research and application value.To date,numerous research on cotton has navigated various aspects,from multi-genome assembly,genome editing,mechanism of fiber development,metabolite biosynthesis,and analysis to genetic breeding.Genomic and 3D genomic studies reveal the origin of cotton species and the spatiotemporal asymmetric chromatin structure in fibers.Mature multiple genome editing systems,such as CRISPR/Cas9,Cas12(Cpf1)and cytidine base editing(CBE),have been widely used in the study of candidate genes affecting fiber development.Based on this,the cotton fiber cell development network has been preliminarily drawn.Among them,the MYB-b HLH-WDR(MBW)transcription factor complex and IAA and BR signaling pathway regulate the initiation;various plant hormones,including ethylene,mediated regulatory network and membrane protein overlap fine-regulate elongation.Multistage transcription factors targeting Ces A 4,7,and 8 specifically dominate the whole process of secondary cell wall thickening.And fluorescently labeled cytoskeletal proteins can observe real-time dynamic changes in fiber development.Furthermore,research on the synthesis of cotton secondary metabolite gossypol,resistance to diseases and insect pests,plant architecture regulation,and seed oil utilization are all conducive to finding more high-quality breeding-related genes and subsequently facilitating the cultivation of better cotton varieties.This review summarizes the paramount research achievements in cotton molecular biology over the last few decades from the above aspects,thereby enabling us to conduct a status review on the current studies of cotton and provide strong theoretical support for the future direction.

High-density Linkage Map of Cultivated Allotetraploid Cotton Based on SSR, TRAP, SRAP and AFLP Markers

A high-density linkage map was constructed for an F2 population derived from an Interspecific cross of cultivated allotetraploid species between Gossypium hirsutum L. and G. barbadense L. A total of 186 F2 individuals from the Interspecific cross of ＂CRI 36 × Hal 7124＂ were genotyped at I 252 polymorphic loci Including a novel marker system, target region amplification polymorphism （TRAP）. The map consists of 1 097 markers, including 697 simple se- quence repeats （SSRs）, 171 TRAPs, 129 sequence-related amplified polymorphisms, 98 amplified fragment length polymorphisms, and two morphological markers, and spanned 4 536.7 cM with an average genetic distance of 4.1 cM per marker. Using 45 duplicated SSR loci among chromosomes, 11 of the 13 pairs of homologous chromosomes were Identified In tetraploid cotton. This map will provide an essential resource for high resolution mapping of quantitative trait loci and molecular breeding in cotton.

Activated carbon coated palygorskite as adsorbent by activation and its adsorption for methylene blue

An activation process for developing the surface and porous structure of palygorskite/carbon（PG/C） nanocomposite using ZnC l2 as activating agent was investigated. The obtained activated PG/C was characterized by X-ray diffraction（XRD）, Fourier transform infrared spectroscopy（FTIR）, field-emission scanning electron microscopy（SEM）, and Brunauer-Emmett-Teller analysis（BET） techniques. The effects of activation conditions were examined,including activation temperature and impregnation ratio. With increased temperature and impregnation ratio, the collapse of the palygorskite crystal structure was found to accelerate and the carbon coated on the surface underwent further carbonization. XRD and SEM data confirmed that the palygorskite structure was destroyed and the carbon structure was developed during activation. The presence of the characteristic absorption peaks of C_C and C-H vibrations in the FTIR spectra suggested the occurrence of aromatization. The BET surface area improved by more than 11-fold（1201 m2/g for activated PG/C vs. 106 m2/g for PG/C） after activation, and the material appeared to be mainly microporous. The maximum adsorption capacity of methylene blue onto the activated PG/C reached 351 mg/g. The activated PG/C demonstrated better compressive strength than activated carbon without palygorskite clay.

Suppression of the homeobox gene HDTF_1 enhances resistance to Verticillium dahliae and Botrytis cinerea in cotton

Development of pathogen-resistant crops, such as fungus-resistant cotton, has significantly reduced chemical application and improved crop yield and quality. However, the mechanism of resistance to cotton pathogens such as Verticillium dahliae is still poorly understood. In this study, we characterized a cotton gene （HDTF1） that was isolated following transcriptome profiling during the resistance response of cotton to V. dahliae. HDTFI putatively encodes a homeodomain transcription factor, and its expression was found to be down-regulated in cotton upon inoculation with V. dahliae and Botrytis cinerea. To characterise the involvement of HDTF1 in the response to these pathogens, we used virusinduced gene silencing （VlGS） to generate HDTFl-silenced cotton. VIGS reduction in HDTF1 expression significantly enhanced cotton plant resistance to both pathogens. HDTF1 silencing resulted in activation of jasmonic acid （JA）-mediated signaling and JA accumulation. However, the silenced plants were not altered in the accumulation of salicylic acid （SA） or the expression of marker genes associated with SA signaling. These results suggest that HDTF1 is a negative regulator of the JA pathway, and resistance to V. dahliae and B. cinerea can be engineered by activation of JA signaling.

Improvement of the activity and SO_(2) tolerance of Sb-modified Mn/PG catalysts for NH_(3)-SCR at a low temperature

A series of MnM/palygorskite(PG)(M=La,W,Mo,Sb,Mg)catalysts was prepared by the wetness co-impregnation method for low-temperature selective catalytic reduction(SCR)of NO with NH_3.Conversion efficiency followed the order Sb>Mo>La>W>Mg.A combination of various physico-chemical techniques was used to investigate the influence of Sb-modified Mn/PG catalysts.MnSb_(0.156)/PG catalyst showed highest NO conversion at low temperatures in the presence of SO_(2) which reveals that addition of Sb oxides effectively enhances the SCR activity of catalysts.A SO_(2) step-wise study showed that MnSb_(0.156)/PG catalyst displays higher durable resistance to SO_(2) than Mn/PG catalyst,where the sulfating of active phase is greatly inhibited after Sb doping.Scanning electron microscopy and X-ray diffraction results showed that Sb loading enhances the dispersion of Mn oxides on the carrier surface.According to the results of characterization analyses,it is suggested that the main reason for the deactivation of Mn/PG is the formation of manganese sulfates which cause the permanent deactivation of Mn-based catalysts.For Sb-doped Mn/PG catalyst,SO_(x) ad-species formed were mainly combined with SbO_(x) rather than MnO_(x).This preferential interaction between SbO_(x) and SO_(2) effectively shields the MnO_(x) as active species from being sulfated by SO_(2) resulting in the improvement of SO_(2) tolerance on Sb-added catalyst.Multiple information support that,owing to the addition of Sb,original formed MnO_(x) crystallite has been completely transformed into highly dispersed amorphous phase accounting for higher SCR activity.