The model of plant nuclear genome evolution. (A) α-proteobacteria and cyanobacteria with RPGs not containing telo-box motif (purple curve) were engulfed in host cell, which possesses euRPGs with telo-boxes. (B) RPGs of endosymbionts (chloroplast and mitochondrion) are transferred into host nuclear genome. (CI) mtRPGs, but not cpRPGs, acquired telo-boxes from host nuclear genome. (CII) both mtRPGs and cpRPGs acquired telo-boxes from host nuclear genome. (DII) under negative selection pressures, telo-boxes of cpRPGs are purged. As a result, mtRPGs and euRPGs share telo-box and exhibit synchronized expression (thick red arrow). On the other hand, cpRPGs do not have telo-boxes in their promoter regions, and the expression coordination between cpRPGs and euRPGs is weak (dashed green arrow).
Wang et al. BMC Evolutionary Biology 2011 11:161 doi:10.1186/1471-2148-11-161