The Distribution Characteristics Of Different Fragments Of Tandem Repeats On Triticeae Chromosomes And Identification Of Dasypyrum Villosum Chromosomes In Wheat Backgrounds

Tandem repeats are abundant in higher eukaryotes.Researches show that the variation of tandem repeats have important effects on the structure of genome and chromosomes,leading to the alteration of gene expression and the changes inphenotype.Therefore,it is valuable to study the distribution characteristics of the tandem repeats in chromosomes.The Dasypyrum villosum provides some elite genes for wheat breeding program.It is also important to identify the Dasypyrum villosum chromosomes in wheat backgrounds.In this study,the metaphase chromosomes of wheat,rye,barley,Dasypyrum villosum,octoploid triticale and wheat-Dasypyrum villosum diploids were analyzed using oligonucleotide probes?oligo probes?and non-denatured fluorescence in situ hybridization?ND-FISH?technology.Oligonucleotide probes were developed from repetitive sequences KU.D15.15,different segments of pSc119.2 and pTa71?rDNA?.The following is the results:1.The oligonucleotide probe Oligo-Ku,which was designed according to repetitive sequence KU.D15.15,combined with oligonucleotide probe?GT?₇ can be used to identify Dasypyrum villosum chromosomes from wheat chromosomes using ND-FISH.Additionally,the oligo probe?GT?₇ can distinguish seven individual chromosomes of Dasypyrum villosum.The probe Oligo-Ku also recognizes the rye chromosome wheat background.2.The sequence 3B.117?117 bp?,which is derived from pSc119.2 family of wheat 3B chromosome,can be divided into 5 segments by?T?n.Seven oligonucleotides were designed based on these five segments,and the seven oligo probe displayed different signal intensity on the same chromosome of wheat,rye or Dasypyrum villosum.The distribution status of different segments from the same tandem sequence are different on different regions of the same chromosome.3.In order to ascertain whether other pSc119.2 sequences have this characteristics,six pSc119.2 sequences were randomly selected from 1B and 3B chromosomes.These sequences were also separated into 5 segments by?T?n,and 36 oligonucleotide probes were designed based on these segments.ND-FISH analysis using these probes showed that the signal strength of these probes was different.The signals of the probes derived from the first,the second,the third and the fifth segments were strong,and the signals of probes derived from the fourth segment were weak.The probes that have the same length and are derived from different segments produced different signal strength,and this indicates that the signal strength of oligo probes was determined by base composition.Additionally,the signal strength of the probes that derived from the whole length of the fifth segments was stronger thant that derived from the partial sequences of the fifth segments,and this indicates that the signal strength of oligo probes was also determined by base length.4.There are four different tandem repeats in wheat rDNA pTa71,and they are A,B,C,and D family,respectively.Oligonucleotide probes were designed based on the repetitive units of the four tandem repeat families,and they were used to analyze the chromosomes of wheat,barley,rye,and Dasypyrum villosum using ND-FISH technology.The probes derived from A family produced strong signals and the signals of the probes derived from the other three families were weak.The two oligo probes,Oligo-pTa71A-1 and Oligo-pTa71A-2,that were derived from the repetitive unit?135 bp?of A family produced the same signal strength on 1B and 6B chromosomes.However,the signal strength of Oligo-pTa71A-1 on 1R and 1V chromosomes was weaker than that of Oligo-pTa71A-2.5.To explore the signal patterns of the similar A repetitive family from rye and and Dasypyrum villosum,a total of four pTa71A-like sequences were cloned from rye and Dasypyrum villosum genomes.Each pTa71A-like sequences was divided into three segments and a total of 12 oligonucleotide probes were designed.ND-FISH analysis indicates that the12 oligo probes produced different signal strength on 1R or 1V chromosomes.It was presumed that the status of the different segments of the pTa71A-like sequence were different on the metaphase 1R or 1V chromosmes.The oligonucleotide probes develope in this study can be used to conveniently identify the chromosomes of Dasypyrum villosum in wheat backgrounds.In addition,the results that different oligo probes derived from the same repetitive sequence displayed different signal strength and different signal loci reflect the different distribution patterns and structural characteristics of these repetitive sequences on chromosomes of Triticeae.