The gain of function mutation blf13 in the barley orthologue of the rice growth regulator NARROW LEAF1 is associated with increased leaf width.
Canopy architecture in cereals plays an important role in determining yield. The width of leaves represents one key aspect of this canopy architecture. However, our understanding of leaf width control in cereals remains incomplete. Classical mutagenesis studies in barely identified multiple morphological mutants, including those with differing leaf widths. Of these, we characterized the broad leaf13 (blf13) mutant in detail. Mutant plants form wider leaves due to increased post-initiation growth and cell proliferation. The mutant phenotype perfectly co-segregated with a semi-dominant, missense mutation in the HvHNT1 gene which affected a highly conserved region of the encoded protein, orthologous to the rice NARROW LEAF1 (NAL1) protein. Causality of this mutation for the blf13 phenotype is further supported by correlative transcriptomic analyses and protein-protein interaction studies showing that the mutant HvNHT1 protein interacts more strongly with a known interactor than wild-type HvHNT1. The mutant HvHNT1 protein also showed stronger homodimerization compared to wild type HvHNT1homodimerization, with a dimer between mutant and wildtype HvHNT1intermediate. Thus, the blf13 mutation parallels known gain-of-function NAL1 alleles in rice that increase leaf width and grain yield, suggesting the blf13 mutation may have a similar agronomic potential in barley. Overall design: Differential gene expression analysis between the barley mutants blf13 and nal1 and their wild types Bonus and Sebastian. Three biological replicates each.