Normal and Abortive Buds Transcriptomic Profiling of Cytoplasmic Male Sterile Line and Its Maintainer.

Bud abortion is the main factor affecting hybrid seeds' yield during broccoli cross breeding when using cytoplasmic male sterile ( CMS) lines. However, the genes associated with bud abortion are poorly understood. We applied RNA sequencing to analyze the transcriptomes of normal and abortive buds of broccoli maintainer and CMS lines. Functional analysis showed that among the 54,753 annotated unigenes obtained, 74 and 21 differentially expressed genes in common were upregulated and downregulated in CMS abortive buds compared with CMS normal buds, maintainer normal, and abortive buds, respectively. Nineteen of the common differentially expressed genes were enriched by GO terms associated with glycosyl hydrolases, reactive oxygen species scavenging, inhibitor, and protein degradation. Ethylene-responsive transcription factor 115 and transcriptional factor basic helix-loop-helix 137 were significantly upregulated; transcription factors DUO1 and PosF21/RF2a/BZIP34 were downregulated in CMS abortive buds compared with the other groups. Genes related to polygalacturonase metabolism, glycosyl hydrolases, oxidation reduction process, phenylalanine metabolism, and phenylpropanoid biosynthesis were significantly changed in CMS abortive buds. Our results increase our understanding of bud abortion, provide a valuable resource for further functional characterization of CMS during bud abortion, and will aid in future cross breeding of crops.