MicroRNA profiles and their control of male gametophyte development in rice.

Plant microRNAs (miRNAs) act as negative regulators of gene expression by slicing target transcripts or inhibiting translation. A number of miRNAs play important roles in development. In order to investigate the potential function of miRNAs during male gametogenesis in rice, we obtained both gene and small RNA expression profiles by combining microarray and high-throughput sequencing technologies. From the microarray datasets, 2,925 male gametophyte-specific genes were identified, including 107 transcription factors and three significant Argonaute genes (AGO12, AGO13, and AGO17). From the sRNA-Seq datasets, 104 unique miRNAs (miRus) were identified, including 47 known miRus and 57 novel miRus; interestingly, most of the new miRus are pollen-specific and not conserved among species. Furthermore, an interactive network of miRNA-target was constructed based on the two datasets. By employing enrichment analysis, the miRNA-regulated targets were found to be involved in both the up and down pathways, but predominantly in the down pathways, including 37 GO biological processes and 32 KEGG pathways. These findings indicate that miRNAs play a broad regulatory role during male gametophyte development in rice.