Origin and evolution of CIN gene family. Plant CINs originated from an orthologous ancestral gene after the endosymbiotic origin of chloroplasts. In charophytes, mosses and basal vascular plants, duplication of CINs (α1 clade) from chloroplast produced CINs in the cytosol with a loss of signal peptides from N-terminals (β clade). No α2 CINs were identified in Selaginella moellendorff, a basal vascular plant. In vascular plants, duplication of CINs (α1) from chloroplast produced CINs in the mitochondria (α2). A) Endosymbiotic gene transfer. B) The first gene duplication event resulted in the loss of signal peptides, hence the appearance of β CIN in the cytosol. C) Whole genome duplication. D) The second gene duplication event leads to the creation of CINs in the mitochondria (α2).