Genome-wide analysis of transcription factors involved in maize embryonic callus formation.

In this study, a maize inbred line with a strong capacity to induce embryonic callus, 18-599R, was used to analyze the transcription factors expressed during embryonic callus formation. A total of 1180 transcription factors were found to be expressed during three key stages of callus induction. Of these, compared with control, 361, 346 and 328 transcription factors were significantly downregulated during stages I, II and III, respectively. In contrast, 355, 372 and 401 transcription factors (TFs) were upregulated during the respective stages. We constructed a transcription factor-mediated regulatory network and found that plant hormone signal transduction was the pathway most significantly enriched among TFs. This pathway includes 48 TFs regulating cell enlargement, cell differentiation, cell division and cell dedifferentiation via the response to plant hormones. Through real-time polymerase chain reaction (PCR) and degradome sequencing, we identified 23 transcription factors that are regulated by miRNA. Through further analysis, ZmMYB138, a member of the MYB transcription factor family localized in the nucleus, was verified to promote embryonic callus formation in the maize embryo through GA signal transduction.