Karyotypes Identification Of Wheat—Thinopyrum Intermedium Derivatives And Transcriptome Analysis Of Alien Addition Line TAI 1-4

Thinopyrum intermedium(2n=42), which is one of the wild relative species of wheat, is a perennial plant of Elytrigia. Th. intermedium possesses numerous agriculturally desirable characteristics, and thus may provide useful genes for wheat genetic improvement. In Elytrigia, Th. intermedium is actually the first successful case to hybridizing with wheat, and many kinds of new germplasm lines were developed from the progenies of common wheat and Th. intermedium, including amphidiploids, addition lines and substitution lines etc. In the present study, fluorescence in situ hybridization(FISH) and genome in situ hybridization(GISH) were used to investigate the karyotypes of Th. intermedium, amphidiploids of wheat(Triticum aestivum) – Th. intermedium(Trititrigia) and the “TAI” series of alien addition lines.Based on GISH using genomic DNA of Pseudoroegneria strigosa and Dasypyrum villosum as probes and DNA from Aegilops tauschii as a block, Th. intermedium genome was divided into three subgenome sets(St,Js and J) and 14 chromosomes(7 pairs) per set. Combination of the results of FISH and GISH, the ideogram of Th. intermedium was established, which has laid an indispensible for further studies.Karyotypic analysis of the five Trititrigia amphidiploids showed that, Zhong1-Zhong5 all had the whole set of wheat chromosomes plus 12-14 Th. intermedium chromosomes, and the constitutions of alien chromosomes were 6Js + 4St-Js + 2J,6Js + 4St-Js + 2J,4Js + 2Js-W + 6St+ 2St-Js,2Js + 2Js-W + 4St-Js + 2S-W + 4St and 2Js + 2Js-W + 4St-Js + 6St. The alien chromosomes in each amphidiploid were all from different subgenomes of Th. intermedium. During the formation of Trititrigia amphidiploids, many translocations have taken places between different genomes of Th.intermedium, and some between common wheat and Th.intermedium.The two sets of alien addition lines(the TAI series) showed highly unstable karyotypes, including loss of alien chromosomes, substitution of wheat chromosomes by alien chromosomes, and substitution and translocation between different chromosomes of wheat. In contrast, we found that the karyotypes of amphidiploids were more stable than those of the addition lines. Changes of karyotypes in addition aliens were more complex and diverse. According to the alien chromosomes from Th.intermedium, which were structurally modified in the Trititrigia amphidiploids, the two sets of alien addition lines were divided into only five types, 3J,7Js,5Js,4Js-D and 5St-Js.For analysis the impact of the alien chromosomes on gene expression, three karyotypes of TAI I-4 were chosen for transcriptome sequencing. The data showed that there were no dramatic changes between wheat and alien addition lines. Alien genes were identified by SNP, and we found that these genes expressed at a much higher level in Th.intermedium than in TAI I-4, suggesting general suppression of gene activity from alien chromosomes by the wheat genome.Further analysis of the mechanisms leading to formation of mixed genomes and the genetic basis of the Tritirigia amphidiploids may provide novel insights into our current understanding of polyploidy speciation in plants.