Transcription profiles reveal sugar and hormone signaling pathways mediating tree branch architecture in apple (Malus domestica Borkh.) grafted on different rootstocks

Abstract

Apple trees grafted on different rootstock types, including vigorous rootstock (VR), dwarfing interstock (DIR), and dwarfing self-rootstock (DSR), are widely planted in production, but the molecular determinants of tree branch architecture growth regulation induced by rootstocks are still not well known. In this study, the branch growth phenotypes of three combinations of 'Fuji' apple trees grafted on different rootstocks (VR: Malus baccata; DIR: Malus baccata/ T337; DSR: T337) were investigated. The VR trees presented the biggest branch architecture. The results showed that the sugar content, sugar metabolism-related enzyme activities, and hormone content all presented obvious differences in the tender leaves and buds of apple trees grafted on these rootstocks. Transcriptomic profiles of the tender leaves adjacent to the top buds allowed us to identify genes that were potentially involved in signaling pathways that mediate the regulatory mechanisms underlying growth differences. In total, 3610 differentially expressed genes (DEGs) were identified through pairwise comparisons. The screened data suggested that sugar metabolism-related genes and complex hormone regulatory networks involved the auxin (IAA), cytokinin (CK), abscisic acid (ABA) and gibberellic acid (GA) pathways, as well as several transcription factors, participated in the complicated growth induction process. Overall, this study provides a framework for analysis of the molecular mechanisms underlying differential tree branch growth of apple trees grafted on different rootstocks.

Influence of Citrus Rootstocks on Scion Growth, Hormone Levels, and Metabolites Profile of ‘Shatangju’ Mandarin (Citrus reticulata Blanco)

“…Anatomical structure, material transport, photosynthesis, plant hormones, and other factors are closely related to dwarfing rootstocks; however, limited studies have shown the relationships between the degree of dwarfing and metabolomics. Earlier studies have shown that small-molecule organic acids can affect plant growth and development [57]. Compared with vigorous ('Shatangju'/'Shatang Mandarin') graft combination, most of the organic acids in the dwarf ('Shatangju'/'Flying Dragon') graft combination was upregulated, which is consistent with previous research results.…”

Physiological, biochemical, and molecular aspects of grafting in fruit trees

“…In addition, overexpression of MdNAC1 gene is associated with dwarfism in transgenic apple by regulating endogenous ABA and BR biosynthesis [ 89 ]. Transcriptomic analysis of apple trees grafted on different rootstocks showed that sugar metabolism-related genes and complex hormone regulatory networks complicated the IAA, CK, ABA, and GA pathways [ 90 ].…”

RNA-Seq combined with population-level analysis reveals important candidate genes related to seed size in flax (Linum usitatissimum L.)

“…The heat map and hierarchical clustering of DEGs were generated using TBtools software with FPKM ( Chen et al., 2020a ). Gene Ontology (GO) enrichment and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis of DEGs were based on all expressed background genes and performed using the GOseq R package ( Young et al., 2010 ) and KOBAS software ( Chen et al., 2020b ). GO and KEGG terms with p adj < 0.05 and p < 0.05 were considered significantly enriched by DEGs, respectively.…”