Brassinosteroid biosynthesis and signaling:Conserved and diversified functions of core genes across multiple plant species

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 abundant opportunities for plant breeding and crop improvement.Enzymes and other proteins involved in the biosynthesis and signaling of BRs are well understood from molecular genetics and phenotypic analysis in Arabidopsis thaliana;however,knowledge of the molecular functions of these genes in other plant species,especially cereal crop plants,is minimal.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 for which additional research is in order.We performed phylogenetic analysis of gene families involved in the biosynthesis and signaling of BRs and re-analyzed publicly available transcriptomic data.Gene trees coupled with expression data provide a valuable guide to supplement future research on BRs in these important crop species,enabling researchers to identify gene-editing targets for BR-related functional studies.

The barren stalk2 Gene Is Required for Axillary Meristem Development in Maize

The diversity of plant architecture is determined by axillary meristems (AMs). AMs are produced from small groups of stem cells in the axils of leaf primordia and generate vegetative branches and reproductive inflorescences . Previous studies identified genes critical for AM development that function in auxin biosynthesis, transport, and signaling. barren stalkl (ba1), a basic helix-loop-helix transcription factor, acts downstream of auxin to control AM formation. Here, we report the cloning and characterization of barren stalk2 (ba2), a mutant that fails to produce ears and has fewer branches and spikelets in the tassel, indicating that ba2 functions in reproductive AM development. Furthermore, the ba2 mutation suppresses tiller growth in the teosinte branchedl mutant, indicating that ba2 also plays an essential role in vegetative AM development. The ba2 gene encodes a protein that co-localizes and heterodimerizes with BA1 in the nucleus . Characterization of the genetic interaction between ba2 and ba1 demonstrates that ba1 shows a gene dosage effect in ba2 mutants, providing further evidence that BA1 and BA2 act together in the same pathway. Characterization of the molecular and genetic interaction between ba2 and additional genes required for the regulation of ba1 further supports this finding. The ba1 and ba2 genes are orthologs of rice genes, LAX PANICLE1 (LAX1) and LAX2, respectively, hence providing insights into pathways controlling AMs development in grasses.