Early regulatory networks driving somatic embryogenesis in Saccharum spp. L. revealed by time-resolved proteomics

The induction of somatic embryogenesis is controlled by various genes and proteins involved in hormonal pathways and stress responses, which act as key regulators of in vitro cellular reprogramming. In this study, we employed a temporal proteomic approach to investigate the underlying molecular mechanisms governing sugarcane (Saccharum spp.) embryogenic callus formation in response to 2,4-dichlorophenoxyacetic acid (2,4-D) during induction. Proteomic profiling revealed 996 differentially accumulated proteins (DAPs) across at least one pairwise comparison among time points (0, 7, 14 and 21 days) during callus induction. These DAPs were classified into different clusters on the basis of their accumulation profile. Proteins involved in embryogenesis, histone epigenetic regulation, hormone responses and protein post-translational modification accumulate during callus induction. The predicted interactions between the TOPLESS protein and auxin response proteins (SKP1, CUL1 and CAND1) are associated with increased accumulation of the histone deacetylase HDT2 protein, a regulator of chromatin condensation, during embryogenic callus initiation. Moreover, proteomic analysis revealed a temporal reduction in methylation cycle enzymes during callus induction, whereas global DNA methylation showed only a slight, non-significant increase, suggesting that additional regulatory layers are present. The identified protein dynamics provide valuable targets for refining somatic embryogenesis protocols and advancing their biotechnological applications in sugarcane. SIGNIFICANCE: Genetic engineering and plant cloning usually involve the induction of embryogenic competence using 2,4-dichlorophenoxyacetic acid (2,4-D). This study presents protein-protein interaction (PPI) networks regulated during the induction of sugarcane callus using 2,4-D, in addition to the morphological aspects of the explant during the process. Proteomic analysis of time series shows the regulation of protein kinases and transcriptional regulators TOPLESS, CUL1, SKP1, CAND1, and ARGONAUTE kinases, revealing mechanisms of activation of induction and multiplication of embryogenic callus. Furthermore, the possible interaction between GH3.8 and SnRK/SAPK kinases suggests a link between hormonal responses.