Biochemistry, Biophysics and Molecular Biology, Roy J. Carver Department of
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In the original definition, synteny implied physical co-localization of genetic loci – i.e., genes – as demonstrated by genetic linkage. This applies to the emerging realization that plants appear to have shuffled their genomes to assemble biosynthetic gene clusters (BGCs) for more specialized metabolism (Nutzmann et al., 2018). However, this assembly process is not well understood. Indeed, the evolutionary timescale over which these BGCs can be assembled, or persist, has not been widely explored. In this issue of New Phytologist Liu et al. (pp. xx – xx) have carried out such analysis of a particular type of BGC in the Brassicaceae. Specifically, by anchoring their studies with oxidosqualene cyclases, the authors are then limited to examining triterpenoid metabolism. Nevertheless, within this context comprehensive bioinformatic analyses were carried out, along with biochemical characterization of selected BGCs. The results strongly indicate that at least these Brassicaceae triterpenoid BGCs exhibit a surprisingly dynamic nature, with many clearly having arisen since the evolutionary divergence of the constituent species examined here. In particular, while synteny is evident, the co-clustered genes generally are differentially ordered and, although often containing members of the same enzymatic subfamilies, phylogenetically distinct. Distinct triterpenoid natural product outcome was shown for two such BGCs by recombinant biochemical characterization. By contrast, others of these BGCs appear to have persisted, with their orthologous function demonstrated by biochemical characterization for one pair, implying consistent selective pressure for retention of the resulting triterpenoids, with strong biological activity recently shown for at least the thalianol product of the pair of BGCs examined here (Huang et al., 2019). Accordingly, these BGCs are readily assembled, yet also can be retained, indicating more than just genomic instability underlies their appearance. While the results reported here strictly pertain to Brassicaceae triterpenoid BGCs, it seems most likely that such dynamic gene shuffling applies to plant BGCs more broadly, providing wider import.
© The Author. New Phytologist © New Phytologist Trust
Peters, Reuben J., "Doing the gene shuffle to close synteny: dynamic assembly of biosynthetic gene clusters" (2020). Biochemistry, Biophysics and Molecular Biology Publications. 309.