Cytoplasmic male sterility (CMS) in flowering plants is usually caused by incompatibility between mitochondrial and nuclear genomes, and can be restored by nuclear genes known as restorer-of-fertility (Rf). | A combined small RNA and transcriptome sequencing analysis reveal regulatory roles of miRNAs during anther development of Upland cotton carrying cytoplasmic male sterile Gossypium harknessii D2 cytoplasm