Ethylene-responsive factor HvERF72 regulates starch synthesis and B-type starch granules initiation in barley

Starch biosynthesis is a pivotal determinant of barley grain quality and yield, yet its regulatory mechanisms remain incompletely characterized. This study identifies HvERF72, an AP2-domain transcription factor, as a key regulator of starch biosynthesis and granule initiation in barley grains. Comparative analyses of CRISPR/Cas9-generated HvERF72 knockout mutants revealed enhanced B-type granule formation and elevated total starch content, whereas overexpression lines exhibited contrasting phenotypes, including reduced starch accumulation and suppressed B-type granule initiation. Transcriptional profiling at 15 DAF indicated significant upregulation of critical starch biosynthesis genes (HvAGPL1,HvAGPS1,HvSS2a,HvSBEI,HvSBEIIb, and HvGBSSI) in mutants, while overexpression lines showed downregulation of these genes. Mechanistic investigation demonstrated that HvERF72 directly binds to GCC-box motifs in the promoter regions of HvSS2a and HvSBEI,repressing their transcription. These findings establishHvERF72as dual-function regulator that modulates starch biosynthesis and B-type granule initiation, providing novel molecular targets for optimizing starch yield and industrial quality in barley breeding programs.