Differentially expressed genes and phenotypic variation in florets among the isogenic Ogura-CMS, DGMS and inbred lines of broccoli

Abstract Background: Male sterility contributes strongly to hybrid seed purity and production in Brassica crops. To detect plant phenotypes and the gene expression patterns involved in bioprocess of an Ogura cytoplasmic male sterility line (Ogura-CMS), a dominant genic male sterility line (DGMS) and their maintainer line, we analyzed the transcriptomes of broccoli florets among the isogenic Ogura-CMS (T54C), DGMS (T54M) and inbred lines (T54S).Results: There were respectively 505, 585 and 469 upregulated genes, and 1109, 1073 and 543 downregulated genes in the comparison groups of T54C and T54M, T54C and T54S, and T54M and T54S. The head weight and head width showed stronger performance in the Ogura-CMS than the DGMS line or maintainer line. The Ogura-CMS line showed poorer performance in seed yield and seed germination than the DGMS line or maintainer line. The DGMS line had longer maturation and flowering periods than the Ogura-CMS and maintainer lines. The plant hormone genes, auxin (TIR1, GH3 and SAUR) and salicylic acid (SA) (NPR1), and adenosine triphosphate-binding cassette (ABC) transporters-related genes (ABCB1 and ATM) were highly up-regulated in T54C compared with T54M or T54S. The brassinosteroid upregulated gene CYCD3 related to the function of late-flowering and delaying senescence in plants, was detected in T54M over two seasons.Conclusions: Among the isogenic Ogura-CMS, DGMS and inbred lines of broccoli, the Ogura-CMS line showed strong performance in head yield than the DGMS line or the inbred line. The DGMS line had longer days to flowering than the Ogura-CMS and inbred lines. However, the inbred line presented a higher seed yield and seed germination rate than the DGMS or Ogura-CMS line. This study found that some potential plant hormone genes, auxin (TIR1, GH3 and SAUR) and SA (NPR1), and ABC transporters related genes (ABCB1 and ATM) might play a key role in regulation of the developmental trait in the Ogura-CMS line. The BR- upregulated gene CYCD3 may function in late-flowering and delaying senescence of broccoli consistent with the investigations conducted over two seasons. Our findings provided a possible explanation for physiological and developmental differences of broccoli among the Ogura-CMS, the DGMS and the inbred lines.