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Integrative Analyses of Metabolome and Transcriptome Reveal Scion–Stock Asymmetry Reduction and Shift of Sugar Metabolism During Graft Junction Formation in Malus Domestica (‘Hanfu’) Homograft

Year: 2025

Type: article

Abstract: Grafting is widely used as a breeding method to enhance productivity and resilience. However, the mechanisms of graft healing remain poorly understood. In this study, we performed Malus domestica (‘Hanfu’) homograft and observed morphological and anatomical changes during the healing process in the graft junction within 40 days after grafting (DAG) with focus on vascular connection between the stock and the scion traced with acid fuchsin dye. The observation showed different phases in the healing process. Phase I, from 0 to 20 DAG, involved formation and proliferation of callus, while phase II, from 20 to 40 DAG, involved reestablishment of vascular connection between the stock and the scion. In order to obtain an in-depth understanding of graft healing processes, transcriptomic and metabolomic changes were analyzed in the stock and the scion tissues at the graft junction in different phases. The transcriptomic data showed different gene expression profiles in the scion and stock in phase I, while gene expression profiles were similar between the scion and the stock during phase II, when differentially expressed genes (DGEs) (20 DAG vs 40 DAG) were highly enriched in pathway of sugar metabolism. In agreement with the transcriptomic result, there was significant difference in metabolite profile between the stock and the scion at 20 DAG, while their metabolomic difference reduced at 40 DAG. Metabolomic analysis highlighted increase in many sugars such as sucrose, glucose, raffinose and melibiose before vascular reconnection (phase I) while decrease in these sugars after vascular reconnection (phase II). Exogenous application of glucose, sucrose, raffinose and melibiose promoted vascular reconnection. The results suggest a shift from asymmetry to relative symmetry in gene expression and metabolism between the stock and the scion during the process of graft junction formation, which involves changes in sugar metabolism. Sugar accumulation is important for the healing process between the stock and the scions.

Source: International Journal of Molecular Sciences

DOI: 10.3390/ijms26115290