Positional cloning and characterization reveal the role of TaSRN-3D and TaBSR1 in the regulation of seminal root number in wheat

center dot Seminal roots play a critical role in water and nutrient absorption, particularly in the early developmental stages of wheat. However, the genes responsible for controlling SRN in wheat remain largely unknown. center dot Genetic mapping and functional analyses identified a candidate gene (TraesCS3D01G137200, TaSRN-3D) encoding a Ser/Thr kinase glycogen synthase kinase 3 (STKc_GSK3) that regulated SRN in wheat. Additionally, experiments involving hormone treatment, nitrate absorption and protein interaction were conducted to explore the regulatory mechanism of TaSRN-3D. center dot Results showed that the TaSRN-3D(4332) allele inhibited seminal roots initiation and development, while loss-of-function mutants showed significantly higher seminal root number (SRN). Exogenous application of epi-brassinolide could increase the SRN in a HS2-allelic background. Furthermore, chlorate sensitivity and N-15 uptake assays revealed that a higher number of seminal roots promoted nitrate accumulation. TaBSR1 (BIN2-related SRN Regulator 1, orthologous to OsGRF4/GL2 in rice) acts as an interactor of TaSRN-3D and promotes TaBSR1 degradation to reduce SRN. center dot This study provides valuable insights into understanding the genetic basis and regulatory network of SRN in wheat, highlighting their roles as potential targets for root-based improvement in wheat breeding.