An analysis of retroposition in plants based on a family of SINEs from XXXX .

@entity1 @entity5599 @entity4335
The identification of a family of SINE retroposons dispersed in the genome of @entity4335 @entity4335 has provided the basis for an evolutionary analysis of retroposition in plants. The repetitive elements (called S1Bn) are 170 bp long and occupy roughly 500 loci by haploid genome. They present characteristic features of SINE retroposons such as a 3' terminal A-rich region, two conserved polymerase III motifs (box A and B), flanking direct repeats of variable sizes, and a primary and secondary sequence homology to several tRNA species. A consensus sequence was made from the alignment of 34 members of the family. The retroposon population was divided into five subfamilies based on several correlated sets of mutations from the consensus. These precise separations in subfamilies based on "diagnostic" mutations and the random distribution of mutations observed inside each subfamily are consistent with the master sequence model proposed for the dispersion of @entity1 retroposons. An independent analysis of each subfamily provides strong evidence for the coexpression of at least three @entity5599 ( @entity5599 ). In contrast to @entity1 retroposition, diagnostic positions are not shared between @entity5599 . We therefore propose that @entity5599 were all derived from a general master sequence (GMS) and independently activated for retroposition after a variable period of random drift. Possible models for plant retroposition are discussed.
