The transcriptome landscape of Arabidopsis male meiocytes from high-throughput sequencing: the complexity and evolution of the meiotic process.

Meiosis is essential for eukaryotic sexual reproduction, with two consecutive rounds of nuclear divisions, allowing production of haploid gametes. Information regarding the meiotic transcriptome should provide valuable clues about global expression patterns and detailed gene activities. Here we used RNA sequencing to explore the transcriptome of a single plant cell type, the Arabidopsis male meiocyte, detecting the expression of approximately 20 000 genes. Transcription of introns of >400 genes was observed, suggesting previously unannotated exons. More than 800 genes may be preferentially expressed in meiocytes, including known meiotic genes. Of the 3378 Pfam gene families in the Arabidopsis genome, 3265 matched meiocyte-expressed genes, and 18 gene families were over-represented in male meiocytes, including transcription factor and other regulatory gene families. Expression was detected for many genes thought to encode meiosis-related proteins, including MutS homologs (MSHs), kinesins and ATPases. We identified more than 1000 orthologous gene clusters that are also expressed in meiotic cells of mouse and fission yeast, including 503 single-copy genes across the three organisms, with a greater number of gene clusters shared between Arabidopsis and mouse than either share with yeast. Interestingly, approximately 5% transposable element genes were apparently transcribed in male meiocytes, with a positive correlation to the transcription of neighboring genes. In summary, our RNA-Seq transcriptome data provide an overview of gene expression in male meiocytes and invaluable information for future functional studies.