Differentially expressed genes in the transition from callus proliferation to differentiation in Ceratopteris richardii

Regeneration is common in plants and transcription factors greatly contribute to this versatility of flowering plants; however, the evolution of this capability has hardly been explored. The callus can be induced from an intact plant rather than an explant in the water fern Ceratopteris richardii and the employed media are very different. The callus was verified having resulted in indirect de novo shoot organogenesis (IDNSO). Hundreds of genes were differentially expressed between the proliferating and the differentiating callus, hinting at significant changes in photosynthesis and hormone response. Many transcription factors were also differentially expressed, providing cues on how the callus proliferated and differentiated. STM-, ANT-, and ESE3-like transcription factor were simultaneously expressed in the vascular-initial-like cells in the callus, thus identifying a key tissue in callus differentiation; furthermore, they might have undergone subfunctionalization or neofunctionalization during evolution. Therefore, IDNSO was considered both conserved and diversified throughout vascular plants. The callus is employed, and there are three reference samples of the differentiating callus and three control samples of the proliferating callus