Genome Composition And Full-length Transcriptome Analysis Of Thinopyrum Intermedium

Thinopyrum intermedium（2n=6x=42,E^eE^eE^bE^bStSt or JJJ^sJ^sStSt）,as a third-order gene source of wheat genetic improvement,is one of the important wild parents which is widely used in wheat genetic improvement because of its excellent characters such as strong disease resistance,stress tolerance and floribunda with large panicle.Thinopyrum intermedium is an allohexaploid and the composition of chromosome is complex.It is helpful to reveal the formation and evolution characteristics of Thinopyrum intermedium and to promote its application in wheat genetic improvement by studying it deeply at the level of chromosomes and transcripts.In this study,molecular cytogenetics and sequencing of full-length transcripts were used to investigate the karyotype composition of Thinopyrum intermedium and its evolutionary relationship with its relative diploid plants.The main results obtained are as follows:1.Using pDb12H developed from Da.villosum and St₂-80 developed from Ps.strigosa as fluorescence probes,fluorescence in situ hybridization was carried out on Th.intermedium,Th.elongatum,Th.bessarabicum,Ps.strigosa and Da.villosum.The results showed that 14chromosomes of Thinopyrum intermedium detected pDb12H signal,28 chromosomes of Thinopyrum intermedium and 14 chromosomes of Thinopyrum intermedium detected St₂-80signal on chromosomes ends and chromosomes arms respectively.According to this result,the chromosomes of Th.intermedium were equally divided into three groups on the basis of different signal locis on chromosomes.Then genomic in situ hybridization of Th.intermedium was carried out by using ssDNA as blocking and genomic DNA of Da.villosum,Th.elongatum and Th.bessarabicum as probe.The result showed that 14 chromosomes of Th.intermedium showed signals of V genome corresponding to chromosomes producing pDb12H hybridization signals in Thinopyrum intermedium;The GISH signal sites of Th.elongatum and Th.bessarabicum on Th.intermedium were similar to each other and corresponded to chromosomes producing St₂-80 signals at both ends in Thinopyrum intermedium.The chromosome groups of Thinopyrum intermedium can be expressed as J^vsJ^vsJ^rJ^rStSt by combining the hybrid signals of Da.Villosum,Th.elongatum,Th.bessarabicum and Ps.strigosa.2.The standard karyotypes of Th.intermedium,Th.elongatum,Th.bessarabicum,Ps.strigosa and Da.villosum were constructed by using oligonucleotide probe sets.It was found that the chromosomes of J^vs motifs were rich in signals,and the karyotypes of J^vss and J^r genomes were significantly different from those of the corresponding diploid phylogenetic materials.At the same time,chromosome in situ hybridization was carried out on three germplasms of Th.intermedium from Afghanistan（PI210990）,Russia（PI325190）and Portugal（PI249146）respectively and the FISH and GISH signals of Thinopyrum intermedium from different sources were basically consistent.3.From the leaves of Th.intermedium and its related plants:Th.ponticum,Th.elongatum,Th.bessarabicum,Ps.strigosa and Da.villosum,the full-length transcripts were sequenced.The phylogenetic tree was constructed on the basis of screening 44 homologous genes in line.Among them,Th.elongatum and Th.bessarabicum were divided into the same branch,the phylogenetic relationship was relatively close,and the relationship was the furthest between Ps.strigosa and all the materials.