HvSL1andHvMADS16promote stamen identity to restrict multiple ovary formation in barley

Abstract

Correct floral development is a consequence of a sophisticated balance between environmental and molecular cues. Floral mutants provide insight into the main genetic determinants that integrate these cues, as well as providing opportunities to assess functional conservation across species. In this study, we characterize the barley (Hordeum vulgare) multiovary mutants mov2.g and mov1 and propose causative gene sequences: a C2H2 zinc-finger HvSL1 and a B-class gene HvMADS16, respectively. In the absence of HvSL1, flowers lack stamens but exhibit functional supernumerary carpels resulting in multiple seeds per floret when artificially pollinated. Deletion of HvMADS16 in mov1 causes homeotic conversion of lodicules and stamens into bract-like organs and carpels that contain non-functional ovules. Based on developmental, genetic, and molecular data we propose a model by which stamen specification in barley is defined by HvSL1 acting upstream of barley B-class genes, specifically the transcriptional up-regulation of HvMADS16. The present work identifies strong conservation of stamen formation pathways with rice, but also reveals intriguing species-specific differences. The findings lay the foundation for a better understanding of floral architecture in Triticeae, a key target for crop improvement.