Comparative transcript profiling of fertile and sterile flower buds from multiple-allele-inherited male sterility in Chinese Cabbage (Brassica campestris L. ssp. pekinensis). Brassica rapa subsp. pekinensis

We studied the causes of sterility underlying multiple-allele-inherited male sterility in Chinese cabbage by identifying differentially expressed genes (DEGs) related to pollen sterility between fertile and sterile flower buds. In this work,we performed transcriptome analysis of mRNA isolated from fertile and sterile buds using Illumina HiSeq 2000 platform sequencing. Approximately 80% of ~229 million high quality paired-end reads were uniquely mapped to the reference genome. In sterile buds, 699 genes were significantly up-regulated and 4,096 genes were down-regulated. Among the DEGs, 28 pollen cell wall-related genes, 53 transcription factor genes, 45 phytohormone-related genes, 20 anther and pollen-related genes, 212 specifically expressed transcripts (SETs), and 417 DEGs located in linkage group R07 were identified. Six transcription factor genes BrAMS, BrMS1, BrbHLH089, BrbHLH091, BrAtMYB103, and BrANAC025, were identified as putative sterility-related genes. The weak auxin signal that is regulated by BrABP1 may be one of the key factors causing pollen sterility observed here. Moreover, several significantly enriched GO terms “cell wall organization or biogenesis” (GO:0071554), “intrinsic to membrane” (GO:0031224), “integral to membrane” (GO:0016021), “hydrolase activity, acting on ester bonds” (GO:0016788) and one significantly enriched pathway “starch and sucrose metabolism” (ath00500) were obtained in this work. qRT-PCR and in situ hybridization validated that our RNA-seq transcriptome analysis was accurate and reliable. This study will lay the foundation for elucidating the molecular mechanism(s) underlying sterility, and provide valuable information for studying multiple-allele-inherited male sterility in Chinese cabbage line ‘AB01’. Overall design: Fertile and sterile flower buds of the GMS line ‘AB01’ were generated by deep sequencing, using Illumina Hiseq 2000 platform; each treatment had three biological replicates.