Domain structure of BCH from green algae and CrtR from cyanobacteria and red algae. Ten BCH-type CHYs from green algae, one CrtR-type CHY from red algae and five CrtRs from cyanobacteria are included. A partial protein sequence (position: 110–400) has been selected for domain structure analysis. The predicted trans-membrane segments are shaded in red. The histidine boxes are shaded in green and Black stars indicate the positions of conserved histidine residues. Ten BCH-type CHYs from green algae includes Prasionphyceae [Micromonas pusilla, Micromonas sp. RCC299, Ostreococcus sp. RCC809, Ostreococcus tauri, and Ostreococcus lucimarinus]. One CrtR-type CHY from the red alga is Cyanidioschyzon merolae. The information of BCH genes from algae is as in Table 1. Five CrtRs from cyanobacteria includes Synechococcus sp. JA-2-3B'a (2–13) [Cyanobase: CYB_0102], Synechococcus sp. JA-3-3Ab [Cyanobase: CYA_1931], Cyanothece sp. PCC 7425 [Cyanobase: Cyan7425_1008], Acaryochloris marina MBIC11017 [Cyanobase: AM1_3637] and Thermosynechococcus elongatus BP-1 [Cyanobase: tlr1900].