Development and Application of Transposable Element-Based Chromosomal Markers for the St Genome in Triticeae.

The St genome, originating from Pseudoroegneria (Nevski) Á. Löve, plays an important role in Triticeae. In this study, the Pseudoroegneria stipifolia genome (2n = 2x = 14, StSt) was screened to identify sequences that could be used for FISH. A total of 163 effective clones were obtained from the genomic plasmid library which was constructed by DNase I digestion of P. stipifolia nuclear genomic DNA. Analysis of these clones identified 112 with characteristics of transposable elements (TEs), 13 with characteristics of tandem repetitive sequences, 8 with characteristics of mRNA sequences, and 30 unknown sequences. Fluorescent signals were detected for 11 of 41 TE sequences on P. stipifolia chromosomes after in situ hybridization and were divided into 4 types according to signal distribution patterns: over the whole St genome chromosomes, telomere to pericentromeric regions, centromere to pericentromeric regions, and terminal regions. The affinity between St and Y genomes was studied using the 11 TE probes in 3 StStYY species. Five TE probes showed no obvious difference between subgenomes, 2 probes displayed divergence only in 2 StStYY species, and 4 probes exhibited significant differences among 3 StStYY species. These results provide a preliminary understanding of the sequence composition of the St genome and enabled 11 novel TE probes to be developed and applied.