Gain of stress-related gene copies through duplication inThellungiella parvula. Genomic regions containing homologs of NHX8, encoding a plasma membrane Li+ transporter , and AVP1, encoding a vacuolar proton transporter , were compared between T. parvula (Tp) and Arabidopsis thaliana (At). Shown are five colinear genes adjacent to NHX8 and AVP1 in the two species. Red arrows indicate duplications. (a)NHX8 is duplicated in tandem into three copies in T. parvula. (b)AVP1 homologs are duplicated and translocated from T. parvula chromosome 5 to chromosome 1. The colinear genomic region in A. thaliana chromosome 1 contains rolling-circle (RC)/helitron transposable elements in the place of an AVP1 homolog (dashed lines), suggesting a possible involvement of transposable elements in the translocation in an ancestor of the two species. The naming of T. parvula genes is according to version 2 of the genome .