Transcriptomics analyses reveal the molecular roadmap and long non-coding RNA landscape of sperm cell lineage development

Sperm cell (SC) lineage development from the haploid microspore to SCs represents a unique biological process in which the microspore generates a larger vegetative cell (VC) and a smaller generative cell (GC) enclosed in the VC, then the GC further develops to functionally specified SCs in the VC for double fertilization. Understanding the mechanisms of SC lineage development remains a critical goal in plant biology. We isolated individual cells of the three cell types, and characterized the genome-wide atlas of long non-coding (lnc) RNAs and mRNAs of haploid SC lineage cells. Sperm cell lineage development involves global repression of genes for pluripotency, somatic development and metabolism following asymmetric microspore division and coordinated upregulation of GC/SC preferential genes. This process is accompanied by progressive loss of the active marks H3K4me3 and H3K9ac, and accumulation of the repressive methylation mark H3K9. The SC lineage has a higher ratio of lncRNAs to mRNAs and preferentially expresses a larger percentage of lncRNAs than does the non-SC lineage. A co-expression network showed that the largest set of lncRNAs in these nodes, with more than 100 links, are GC-preferential, and a small proportion of lncRNAs co-express with their neighboring genes. Single molecular fluorescence in situ hybridization showed that several candidate genes may be markers distinguishing the three cell types of the SC lineage. Our findings reveal the molecular programming and potential roles of lncRNAs in SC lineage development.