Figure 4

Conservation of heme oxygenase 1 (HO1) enzymes in land plants. HO enzymes mediate the oxidative cleavage of the heme ring to produce biliverdin IXα, the committed step towards the biosynthesis of the phytochrome chromophores, such as PQB. Public database searches identified HO1 enzyme genes from a wide array of plant species, including the earliest land plants (bryophyte and lycophyte). Amino acid sequences of the HO1 proteins were retrieved from the NCBI database (http://www.ncbi.nlm.nih.gov/protein). A phylogenetic tree was constructed using the MEGA7 software with the neighbor-joining method.