Evaluating Tartary Buckwheat Genotypes with High Callus Induction Rates and the Transcriptomic Profiling during Callus Formation

Due to their complex genotypes, low in vitro regeneration rates, and difficulty in obtaining transgenic plants, studies concerning basic biological research and molecular breeding in Tartary buckwheat (TB) are greatly limited. In this study, the hypocotyls of 60 genotypes of TB (TBC1~60) were used as explants. Of these, TBC14 was selected due to a high callus induction rate of 97.78% under dark and a proliferation coefficient (PC) of 28.2 when cultured on MS medium supplemented with 2.0 mg/L of 2,4-D and 1.5 mg/L of 6-BA. Subsequently, the samples of the calli obtained from TBC14 were collected at 0, 10, 20, and 30 d, and their transcriptomes were sequenced where identified. GO enrichment led to the detection of the most significant active gene set, which was the DNA binding transcription factor activity. The DEGs related to the pathways concerning metabolism, the biosynthesis of secondary metabolites, and hormone signal transduction were the most enriched in the KEGG database. The sets of MYB, AP2/ERF, and bHLH TFs exhibited the highest number of DEGs. Using this enrichment analysis, 421 genes encoding TFs, 47 auxin- and cytokinin-related genes, and 6 signal transduction-associated genes were screened that may play significant roles in callus formation (CF) in TB. Furthermore, FtPinG0008123200.01 (bZIP), a key gene promoting CF, was screened in terms of the weighted gene co-expression network associated with the various stages of CF. Our study not only provides valuable information about the molecular mechanism of CF but also reveals new genes involved in this process.