Global Profiling of Alternative Splicing in Callus Induction of Immature Maize Embryo

Callus induction in plants is similar to pluripotent stem cell induction in animals and can incite global changes in gene expression. Alternative splicing is considered a key factor underlying functional complexity and function in the induction of pluripotent stem cells in animals. However, the role of alternative splicing in plant callus induction remains unclear. We performed high-throughput RNA sequencing of maize callus induced on a callus induction medium (CIM) at different stages and recorded global alternative splicing changes. At every stage, over 20,000 alternative splicing events were detected, and the numbers slightly increased with callus induction. In total, 648 to 2580 genes were found to exhibit significant alternative splicing changes during callus induction-mainly those that belong to the spliceosome, metabolic pathways, and mRNA surveillance pathways. It was also found that alternative splicing can function alongside transcriptional regulation to contribute to callus induction. Especially, ZmWOX11, whose orthologous gene in Arabidopsis plays a vital role in the first-step cell fate transition of callus induction, was found to exhibit alternative splicing and expression level changes during callus induction. Our results establish a foundation from which researchers can further explore the molecular mechanism of callus induction in maize, especially at alternative splicing level.