Genome Constitution Of Hystrix Komarovii (Poaceae: Triticeae)

Hystrix Moench is a small perennial genus in the tribe Triticeae(Poaceae).It was established by Moench(1794) according to the distinct morphological character of lacking glumes,or long setaceous awm-shaped ones,if present.The type species is Hystrix patula Moench.Since then,eleven species have been included in Hystrix,and three of them growing in China.Cytologically,Church(1967) reported that Hy.patula had a close affinity to species of the Elymus canadensis L.complex.Dewey(1984) reported that Hy.patula had the StH genomes and included Hystrix in the genus Elymus L.according to genome classification. Jensen et al.(1997) reported that Elymus coreanus(Hy.coreana) and E.californicus(Hy. californica) have the same genome constitution of Leymus(NsXm),and included them in the genus Leymus Hochst.Thus,the taxonomy of Hystrix becomes complicated.The definition of Hystrix and its precise taxonomic rank are still under discussion.The main dispute is whether included the species of Hystrix in Hystrix,or regard it as a part of Elymus or Leymus.Hystrix komarovii(Roshev.) Ohwi is a tetraploid species(2n=4x=28) in Hystrix. Ellenskog-Staam et al.(2007) reported that Hy.komarovii likely had a variant of the StH genome based on the results of GISH and Southern genomic hybridization.However,Zhang et al.(2009) suggested that Hy.komarovii might have similar NsXm genomes to Hy.coreana and Hy.duthiei,but not the StH genomes of H.patula based on the nrDNA ITS sequences.In order to investigate the genome constitution of Hy.komarovii,genomic-specific RAPD markers,genomic in situ hybridization(GISH) and nrDNA ITS sequences analysis of Hy. komarovii,the other four Hystrix species and the related species were carried out in this study. The main results are as follows:1.Five genomic-specific RAPD markers representing the St,H,Ns,E~e and E~b genome respectively were utilized to determine the genome relationships among Hy.komarovii and the related species.The results showed that:(1) the St and H genomic-specific RAPD markers presented in Hy.patula and other Elymus species containing St and H genome,but absent in Hy.komarovii,Hy.duthiei ssp.duthiei,Hy.duthiei ssp.longearistata and Hy. coreana;(2) the Ns genomic-specific RAPD marker presented in Hy.komarovii as well as in Hy.duthiei ssp.duthiei,Hy.duthiei ssp.longearistata and Hy.coreana,but absent in Hy. patula;(3) the E~e and E~b genomic-specific RAPD markers absent in either Leymus or Hystrix species.The results suggested that Hy.komarovii might contain the Ns genome,but absent the St and H genome.2.Four genomic DNA probes containing St,H,Ns,E~e genome,respectively,were used in genomic in situ hybridization(GISH) for detecting the presence of these four genomes in Hy.komarovii and the other Hystrix species.The results showed that:(1) Hy.patula had the St and H genome;(2) Hy.duthiei ssp.duthiei,Hy.duthiei ssp.longearistata and Hy.coreana had the Ns genome of Psathyrostachys and the other genome shared one or a few repetitive sequences with the E~e genome;(3) the 14 chromosomes showed strong green fluorescence when 28 chromosomes of Hy.komarovii were hybridized with the probed Ns-genome DNA of Psathyrostachys,while the 14 chromosomes showed strong or weak green hybridization signals when the chromosomes of Hy.komarovii were hybridized with the probed E~e-genome DNA of Lophopyrum elongatum.The results suggested that Hy.komarovii had the Ns genome of Psathyrostachys,and the other genome of Hy.komarovii had high homology with the E~e genome of Lophopyrum.3.To estimate the phylogenetic relationships of Hy.komarovii and the related species, nuclear ribosomal internal transcribed spacer(ITS) of 14 taxa in Triticeae containing St,H, Ns,E~e,E~b,StH and NsXm genomes were analyzed.In the ITS tree,Hy.komarovii,Hy. duthiei ssp.duthiei,Hy.duthiei ssp.longearistata and Hy.coreana formed one group with the species from Psathyrostachys and Leymus,which indicated a close phylogenetic relationship among these species.Hy.patula was claded with other two Elymus species.The results indicate that Hy.komarovii might had the NsXm genomes of Leymus,which is in agreement with those of cytology and GISH.4.According to the results of genomic-specific RAPD assay,GISH,and nrDNA ITS sequenes analysis in the present study,it is concluded that Hy.komarovii had a set of Ns genome and the other genome had high homology with the E~e genome of Lophopyrum.Hy. komarovii absent the StH genomes of Elymus.