Single-cell transcriptome sequencing (ScRNA-seq) uncovers the regulatory role of lodicule cells in rice floret opening (FO).

Floret opening (FO) in rice (Oryza sativa L.) is triggered by lodicule swelling. However, the regulatory mechanisms underlying lodicule-mediated FO remain largely unclear. In particular, it is unknown whether distinct floral cell types coordinately regulate lodicule osmotic potential and cell wall remodeling. To address this question, we performed single-cell transcriptome sequencing on spikelets sampled at pre-floret opening and FO stages. This study demonstrates strong communication between phloem and lodicule cells during FO, potentially involving transport of calcium ions, soluble sugars, and water. These osmolytes contribute to lowering lodicule osmotic potential, thereby facilitating swelling. Multiple FO genes involved in lodicule cell wall remodeling showed heterogeneous activation in lodicule cells, suggesting fine regulation of cell wall remodeling and cell deformation. Together, these findings provide single-cell insights into lodicule control of FO. In addition, we identified multiple FO regulators, providing genetic resources for improving FO.