Abstract

Background

Extensive DNA rearrangement of genic colinearity, as revealed by comparison of orthologous genomic regions, has been shown to be a general concept describing evolutionary dynamics of plant genomes. However, the nature, timing, lineages and adaptation of local genomic rearrangement in closely related species (e.g., within a genus) and haplotype variation of genomic rearrangement within populations have not been well documented.

Results

We previously identified a hotspot for genic rearrangement and transposon accumulation in theOrp region of Asian rice (Oryza sativa, AA) by comparison with its orthologous region in sorghum. Here, we report the comparative analysis of this region with its orthologous regions in the wild progenitor species (O. nivara, AA) of Asian rice and African rice (O. glaberrima) using the BB genome Oryza species (O. punctata) as an outgroup, and investigation of transposon insertion sites and a segmental inversion event in the AA genomes at the population level. We found thatOrp region was primarily and recently expanded in the Asian rice species O. sativa and O. nivara. LTR-retrotransposons shared by the three AA-genomic regions have been fixed in all the 94 varieties that represent different populations of the AA-genome species/subspecies, indicating their adaptive role in genome differentiation. However, LTR-retrotransposons unique to either O. nivaraor O. sativa regions exhibited dramatic haplotype variation regarding their presence or absence between or within populations/subpopulations.

Conclusions

The LTR-retrotransposon insertion hotspot in the Orp region was formed recently, independently and concurrently in different AA-genome species, and that the genic rearrangements detected in different species appear to be differentially triggered by transposable elements. This region is located near the end of the short arm of chromosome 8 and contains a high proportion of LTR-retrotransposons similar to observed in the centromeric region of this same chromosome, and thus may represent a genomic region that has recently switched from euchromatic to heterochromatic states. The haplotype variation of LTR-retrotransposon insertions within this region reveals substantial admixture among various subpopulations as established by molecular markers at the whole genome level, and can be used to develop retrotransposon junction markers for simple and rapid classification of O. sativa germplasm.

Comments

This is the publisher pdf of Zhixi Tian, Yanjun Yu, Feng Lin, Yeisoo Yu, Phillip J SanMiguel, Rod A Wing, Susan R McCouch, Jianxin Ma, Scott A Jackson. Exceptional lability of a genomic complex in rice and its close relatives revealed by interspecific and intraspecific comparison and population analysis. BMC Genomics 2011, 12:142 (8 March 2011) and is available at: 10.1186/1471-2164-12-142.

Date of this Version

3-8-2011

DOI

10.1186/1471-2164-12-142

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