Abstract
Several cytochromes P450 (P450s) are involved in biosynthesis and catabolism of phtohormones in flowering plants. Genome sequencing projects of Physcomitrella patents and Selaginella moellendorffii have revealed that some orthologous genes to phytohormone-related P450s from the flowering plants may be present in bryophyte and pteridophyte. We think that the comparative analysis of plant P450s conserved across the evolutionary stages can give us a clue to study the evolutionary aspects of phytohormone homeostasis. In this study, we performed functional analysis of P450s involved in abscisic acid (ABA) catabolism from P. patents and S. moellendorffii. While there are no CYP707A-family genes in the genome of P. patents, we have found five CYP707-family genes, CYP707A20, 707A43, 707B1, 707B2, and 707C1 from S. moellendorffii. The full-length ORFs of the P450 genes were isolated by RT-PCR, and the recombinant P450 proteins were expressed with a baculovirus-insect cell system in order to analyze their catalytic activities in vitro. CYP707A20 and 707A43 showed the ABA 8'-hydroxylase activity, while the other three P450s did not metabolize ABA at all.
