Defining the developmental program leading to meiosis in maize

In multicellular organisms, the entry into meiosis is a complex process characterized by increasing levels of meiotic specialization. We used single-cell RNA-sequencing to reconstruct the developmental program into meiosis in maize. We observed a smooth continuum of expression stages leading up to meiosis, followed by a sharp reorganization of the transcriptome in early meiotic prophase. This latter transcriptional shift was dramatic, with 26.7% of expressed genes changing by 2 fold or more, and occurred just prior to a proposed cell cycle checkpoint. Changes in cell physiology accompanied the nuclear events of meiosis, including a decrease in protein translation capacity and increase in membrane-bound organelles. We further identified differences in gene expression between the mitotic and meiotic cell cycles. Our results uncover a multi-step pathway into meiosis and highlight the power of single cell RNA-seq to define developmental transitions.