Lineage‐specific evolution of flavin‐containing monooxygenases involved in aliphatic glucosinolate side‐chain modification.

Abstract: Glucosinolates, a class of specialized metabolites specific to the order Brassicales, have diverse bioactivities that are largely dependent on the structures of their side chains. Flavin‐containing monooxygenases (FMOs) encoded by the <italic>FMOGS‐OX</italic> genes have been found to catalyze side‐chain modifications during the synthesis of methionine‐derived aliphatic glucosinolates. Seven <italic>FMOGS‐OX</italic> genes have been identified in <italic>Arabidopsis</italic> Heynh., but the evolution of these genes in the Brassicaceae, a family including many economically important vegetables, is poorly understood. In this study, the phylogenetic and syntenic relationships of the <italic>FMOGS‐OX</italic> genes belonging to 12 sequenced Brassicaceae species were analyzed. Our results showed that the <italic>FMOGS‐OX</italic> genes included two tandem arrays, the <italic>FMOGS‐OX2‐4</italic> group (group A) and the <italic>FMOGS‐OX5‐7</italic> group (group B). The evolutionary histories of the <italic>FMOGS‐OX</italic> groups A and B were similar across the Brassicaceae, but two lineage‐specific evolutionary routes developed after these two separate species lineages diverged from <italic>Aethionema arabicum</italic> (L.) Andrz. ex DC. In the lineage I route, <italic>FMOGS‐OX</italic> gene copies tended to increase due to frequent tandem duplication events in most species and a whole genome triplication in <italic>Camelina sativa</italic> (L.) Crantz. In the lineage II route, gene copies decreased due to deletion events. Combining these results with those of previous studies, we speculated that the <italic>FMOGS‐OX</italic> genes were derived from an ancestral gene with a broad expression distribution and a broad range of substrates, which then underwent subfunctionalization to generate progeny limited in either spatial expression or substrate structure. Furthermore, the absence of FMOGS‐OX5 substrates in some <italic>FMOGS‐OX5</italic>‐containing species may suggest neofunctionalization of these genes. [ABSTRACT FROM AUTHOR]