A SQUAMOSA promoter-binding protein-like transcription factor controls crop ideotype for high productivity in barley

Authors: Yang, Shengming; Overlander-Chen, Megan; Carlson, Craig; Fiedler, Jason

Submitted to: Plant Direct
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/29/2022
Publication Date: 9/12/2022
Citation: Yang, S., Overlander-Chen, M., Carlson, C.H., Fiedler, J.D. 2022. A SQUAMOSA promoter-binding protein-like transcription factor controls crop ideotype for high productivity in barley. Plant Direct. 6(9). Article e450. https://doi.org/10.1002/pld3.450.
DOI: https://doi.org/10.1002/pld3.450

Interpretive Summary: The erect leaf phenotype in cereal crops is a highly desirable trait that enhances light capture capacity and photosynthetic efficiency under dense planting. However, this favorable phenotype is generally coupled with undesirable agronomic traits, and the molecular mechanism controlling leaf angle has not been fully understood. In the present study, we identified a gene regulating leaf angle in barley and found that this gene encoded a protein that regulates other genes. Mutant plants that don’t have this gene have a disruption in the formation of certain structures at the base of barley leaves, which results in a more erect leaf trait. More importantly, we found that the mutant shows similar yield and agronomic traits to non-mutant plants. Therefore, our research has provided genetic material for breeders to improve barley yield using a suitable architecture for dense planting, and it also has provided a new gene target for barley geneticists to optimize light use efficiency under field conditions.

Technical Abstract: Crop architecture is important for light capture and tightly affects economic yield under field condition. Understanding the genetic regulation of this important trait is crucial in the ongoing development of high-yielding barley cultivars. Here, we conducted map-based cloning of the Liguleless 1 (Lig 1) regulating leaf angle in barley. A loss-of-function mutant of Lig 1 obtained by spontaneous mutation lacked ligules and auricles, which resulted in smaller leaf angles. A compact architecture caused by erect leaves is an especially desirable target trait to increase yield by limiting light competition in high-density plantings. Genetic mapping anchored the Lig 1 gene onto 2H within an '300-kb region, wherein we identified in the mutant a 20-kb deletion in a SQUAMOSA promoter-binding protein-like (SPL) gene, HORVU.MOREX.r3.2HG0202650. Phylogenetic analysis suggested this SPL in barley might be a homolog of leaf angle regulators Zmlg1 and TaSPL8 in maize and wheat, respectively. Using CRISPR technology, we knocked out the SPL-encoding gene and phenocopied the Lig1 mutant, corroborating HORVU.MOREX.r3.2HG0202650 is the Lig1 gene. Importantly, we demonstrate through cloning of Lig1 that this SPL transcription factor is conserved in monocots, which provides a target for gene manipulation to maximize light interception capability and photosynthesis efficiency in high-density plantings.