title: Evolution of parental ITS regions of nuclear rDNA in allopolyploid Aegilops (Poaceae) species.
abstract: The genus Aegilops comprises approximately 25 diploid, tetraploid and hexaploid species, in which the genome types of all allopolyploids involve either U or D genome, or both of them. The internal transcribed spacer (ITS) region of 18S-26S nuclear ribosomal DNA (rDNA) from 11 allopolyploid species and 7 related diploid species in the genus were directly sequenced by pooled PCR products. Phylogenetic analyses for tracing evolutionary patterns of parental rDNA in allopolyploid species were performed using the neighbor-joining method. The D genome involved tree included three clades (CC-DDCC, DDMM-DDMMSS-DDMMUU, and MM-MhMh-DDNN), but did not include Ae. squarrosa (DD). It indicated that the rDNA of ancestral D genome had been somewhat differentiated in allopolyploids. The U genome involved tree showed that the allopolyploids and their common ancestor, Ae. umbellulata, formed a clade, suggesting that rDNA in UUMM and UUSS genomes has been homogenizing toward that of ancestral U genome. The phylogenetic pattern of U genome based on ITS sequences also supported the "pivotal-differential" hypothesis.
authors.affiliation: College of Life Sciences, Wuhan University, Hubei, China. jbwang@whu.edu.cn
authors.forename: J B
authors.initials: JB
authors.lastname: Wang
authors.forename: C
authors.initials: C
authors.lastname: Wang
authors.forename: S H
authors.initials: SH
authors.lastname: Shi
authors.forename: Y
authors.initials: Y
authors.lastname: Zhong
mesh_terms: D018744:DNA, Plant / Q000235:genetics; D004275:DNA, Ribosomal / Q000235:genetics*; D019143:Evolution, Molecular; D010802:Phylogeny; D006109:Poaceae / Q000235:genetics*; D011123:Polyploidy; D012091:Repetitive Sequences, Nucleic Acid / Q000235:genetics*; D016415:Sequence Alignment; D017422:Sequence Analysis, DNA; D014158:Transcription, Genetic / Q000235:genetics
chemical_list: D018744:DNA, Plant; D004275:DNA, Ribosomal