A Neighbor Joining phylogenetic analysis of the CO and COLs family from Arabidopsis (At), rice (Os), soybean (Gm), G. raimondii (Gr) and G. hirsutum (Gh). Multiple alignments were generated using ClustalW [46]. The phylogenetic tree was constructed using MEGA5.1 [47]. Bootstrap values for 1,000 re-samplings were shown on each branch. The 122 CO homologs from five plant species were identified by homology searches in GenBank database using Arabidopsis CO and COL proteins as entry. The clades were divided into three groups, branches of which were marked in differently colors. AtCO, OsHd1, GhCOL1-A and GhCOL1-D were indicated using a black prism.