Regulation by sugar and hormone signaling of the growth of Brassica napus L. axillary buds at the transcriptome level

Branching is an important factor affecting the yield of Brassica napus L. Generally, however, field-grown B. napus cannot develop branches from the middle and lower parts of the plant, although axillary buds are present in these parts. To explore the cause of this phenomenon at the mRNA level, we analyzed buds from the top, upper, middle and lower parts of B. napus by RNA-SEq. In total, 27,992 expressed genes were found, 479 of which were considered to be closely related to axillary bud development. Genes related to the regulation of sugar signaling and plant hormone signal transduction were subjected to Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analyses. Seven types of transcription factors, including phytochrome-interacting factors (PIFs), homeobox 1 (HB-1), light sensitive hypocotyls 4 (LSH4), BRANCHED 1 (BRC1), WRKY DNA-binding proteins (WRKYs) and Transducin/WD40 repeat-like superfamily proteins (WD40s), were enriched. The soluble sugar content in the axillary buds was assessed and found to differ significantly among the four regions of the plant; in short, the soluble sugar content decreased from top to bottom. In this study, we provide a transcriptional profile of axillary buds from different parts of B. napus plants; these data will be important for future studies on the growth and development of axillary buds.