Differential gene expression networks and auxin responses during maize callus induction from explant tissues with contrasting embryogenic potential

Abstract

Maize somatic embryogenesis process depends on explant characteristics and genotype. The relationship between explant developmental timing and embryogenic potential of derived tissues is still poorly understood. The present work explored the adjustments of transcriptomes and proteomes from explants with contrasting embryogenic potential – immature and mature zygotic embryos from the Tuxpeño VS-535 genotype – during callus induction. Differentially accumulated transcripts and proteins were represented by oxidation/reduction, stress response, and metabolic process adjustments during the dedifferentiation of both explants. However, the explant with high embryogenic potential and derived callus displayed more significant enrichment in cell proliferation and plant hormone signal transduction pathways. Between the differentially accumulated proteins, it is of notice a significantly higher enrichment of catabolic and anoxia processes in non-embryogenic as opposed to anabolic and oxidation-reduction processes in the embryogenic callus induction. Transcription factors such as Auxin Response Factors (ARFs), signal transduction (Homeobox; HB), and embryogenesis-related AP2-EREB mRNAs characterized the immature embryos. Activator and repressor ARFs substantially differed at the early stages of callus induction between immature and mature embryo explants. The overall analysis of these findings helps to understand the molecular basis of gene expression regulation during callus dedifferentiation and auxin responses from maize explants with contrasting embryogenic potential.

Significance

This work contributes with overall transcript and protein patterns during the callus induction phase of Mexican landrace Tuxpeño VS-535 maize somatic embryogenesis from immature and mature embryos. Using comparisons between explants, between each explant and the induced callus, and between callus, differential biological process enrichment at transcript and protein levels for the embryogenic callus induction indicated key roles for cell proliferation, hormone signaling and biosynthetic processes for embryogenic callus induction. Furthermore, a battery of TF family enriched in the immature embryo, including several auxin response factors support the differential gene expression reprogramming during dedifferentiation from explants with contrasting embryogenic potential in maize somatic embryogenesis.