structure and evolution of apetala3, a sex-linked gene in silene latifoliaapetala3的结构和演变,与性别有关的基因在硅宾latifolia.pdf

Cegan et al. BMC Plant Biology 2010, 10:180 /1471-2229/10/180 RESEARCH ARTICLE Open Access Structure and evolution of Apetala3, a sex-linked gene in Silene latifolia 1,2 3 1 4 4 1 Radim Cegan , Gabriel AB Marais , Hana Kubekova , Nicolas Blavet , Alex Widmer , Boris Vyskot , 5 5 1* Jaroslav Doležel , Jan Šafář , Roman Hobza Abstract Background: The evolution of sex chromosomes is often accompanied by gene or chromosome rearrangements. Recently, the gene AP3 was characterized in the dioecious plant species Silene latifolia. It was suggested that this gene had been transferred from an autosome to the Y chromosome. Results: In the present study we provide evidence for the existence of an X linked copy of the AP3 gene. We further show that the Y copy is probably located in a chromosomal region where recombination restriction occurred during the first steps of sex chromosome evolution. A comparison of X and Y copies did not reveal any clear signs of degenerative processes in exon regions. Instead, both X and Y copies show evidence for relaxed selection compared to the autosomal orthologues in S. vulgaris and S. conica. We further found that promoter sequences differ significantly. Comparison of the genic region of AP3 between the X and Y alleles and the corresponding autosomal copies in the gynodioecious species S. vulgaris revealed a massive accumulation of retrotransposons within one intron of the Y copy of AP3. Analysis of the genomic distribution of these repetitive elements does not indicate that these elements played an important role in the size increase characteristic of the Y chromosome. However, in silico expression analysis shows biased e