Conservation and diversification of genes regulating brassinosteroid biosynthesis and signaling

Brassinosteroids (BRs) are important regulators that control myriad aspects of plant growth and development including biotic and abiotic stress responses, such that modulating BR homeostasis and signaling presents enormous opportunities for plant breeding and crop improvement. Enzymes and proteins involved in the biosynthesis and signaling of BRs are well understood from molecular genetics and phenotypic analysis in Arabidopsis thaliana; however, knowledge of molecular function of these genes in other plant species, especially cereal crop plants, is highly limited. In this manuscript, we comprehensively review functional studies of BR genes in Arabidopsis, maize, rice, Setaria, Brachypodium, and soybean to identify conserved and diversified functions across plant species, and to highlight cases where additional research is in order. We performed phylogenetic analysis of gene families known to be involved in biosynthesis and signaling of BRs and re-analyzed publicly available transcriptomic data. Gene trees coupled to expression data provide a useful guide to supplement future research on BRs in these important crop species, such as to allow researchers to identify genes to target through gene editing techniques to perform BR-related functional studies.