MADS1-regulated lemma and awn development benefits barley yield
Floral organ shape and size in cereal crops can affect grain size and yield, so genes that regulate their development are promising breeding targets. The lemma, which protects inner floral organs, can physically constrain grain growth; while the awn, a needle-like extension of the lemma, creates photosynthates to promote grain fill. Although several genes and modules controlling grain size and awn/lemma growth in rice have been characterized, these processes, and the relationships between them, are not well understood for barley and wheat. Here, we demonstrate that the barley E-class gene HvMADS1 positively regulates awn length and lemma width, leading to increased grain size and weight. Cytological data indicated that MADS1 promotes grain growth by promoting cell proliferation, while multi-omics data revealed MADS1 target genes associated with cell cycle, phytohormone signaling, and developmental processes. We defined two direct targets of MADS1 regulation, HvSHI and HvDL, whose knockout mutants mimic awn and/or lemma phenotypes of mads1 mutants; and demonstrated that MADS1 interacts APETALA2 (A-class) to synergistically activate downstream genes in awn/lemma development. Notably, we found that MADS1 function remains conserved in wheat, promoting cell proliferation to increase awn length. These findings extend our understanding of MADS1 function in floral organ development to inform strategies for Triticeae crop improvement. Three replicates of barley tissues were collected for RNA extraction: lemma and awn from the central part of lemma and awn from WT and mads1 mutants for RNA-seq and RT-qPCR Overall design: Comparative gene expression profiling analysis of RNA-seq data for mads1 and wild type barley