Study On Fertility-Related MicroRNAs Of S Type CMS In Maize

Cytoplasmic male sterility (CMS) wildly exists in the plant world. It has been used as an important resource in crop hybridization breeding. The exploration of the regulatory mechanism in male sterility and fertility restoration can help us to better understand and utilize this phenomenon. MicroRNA (miRNA) is a class of～21nt small RNA. It is recognized to participate in almost every stage of plant development and plays a significant regulatory role in different kinds of biological processes.This study attempted to search for miRNAs related to fertility by investigating the expression profiles of maize pollen miRNAs from an S type CMS line S-Mo17rf3rf3(rf3) and its fertility restored line S-Mol7Ri3Rf3(Rf3). Targets of these miRNAs were predicted and analyzed to explore the possible role of miRNAs in fertility regulation. The results of this study are listed as follows:(1) Through the analysis of Solexa high-throughput sequencing,100known miRNAs belonging to20families were recognized and81novel miRNAs belonging to44families were predicted;(2) Of all the known miRNAs, two miRNAs showed extremely significant expression difference between the two lines and7miRNAs had significant differential expression levels. There were also21miRNAs displaying expression difference between1.5fold and2fold. All of the30miRNAs expressed more strongly in rf3except miR160f;(3) Among those30miRNAs,11miRNAs (miR156k, miR159a/b, miR164a/b/c/d and miR167a/b/c/d) with higher expression levels were verified using stem-loop RT-qPCR. Their expression trends were consistent with the sequencing result;(4) Targets of miRNAs were predicted by Targetfinder software and analyzed by Gene Ontology classification and annotation. Many targets of known miRNAs were found to have DNA-binding function and participated in processes like transcription regulation and hormone response.By studying the functions of miRNAs and their targets, we find that these miRNAs play a vital role in plant growth and development. The miRNAs verified by stem-loop RT-qPCR have been reported to regulate floral development. We propose that these four miRNAs all take part in the regulation of fertility in various degrees.