Molecular and physiological characterization of brassinosteroid receptor BRI1 mutants in Sorghum bicolor

* The high sequence and structural similarities between BRI1 brassinosteroid receptors of Arabidopsis (AtBRI1) and sorghum (SbBRI1) prompted us to study the functionally conserved roles of BRI in both organisms. * Introducing sorghum SbBRI1 in Arabidopsis bri1 mutants restores defective growth and complements developmental phenotypes to WT levels. * Sorghum mutants for SbBRI1 receptors show defective BR sensitivity and results in impaired growth and development throughout the entire sorghum life cycle. Embryonic analysis of sorghum primary roots traced the root growth and development at the early stages, revealing the role of SbBRI1 in BR perception during cell division and BR sensing. RNA-seq of SbBRI1 mutants support the roles of SbBRI1 in cell wall biosynthesis and remodeling. * Together, these results uncover that sorghum SbBRI1 receptor protein play functionally conserved roles in plant growth and development. To study the role of BRI1 in sorghum in more molecular detail, RNA-seq analysis was used to investigate which processes are transcriptionally regulated by SbBRI1 in bri1-ems72 roots against their sibling WT-ems72 using BC2F2 plants (ko vs wt). For each biological replicate, a minimum of 6 bri1-ems72 and WT-ems72 roots were pooled to homogeneize as much as possible the genetic background of the samples. RNA was extracted using Maxwell 16 LEV PLANT RNA KIT (PROMEGA) and quality checked using Bioanalyzer. A total of 3 biological replicates were taken for each genotype.