PmLBD3 leads to dwarfing through auxin and brassinolide signaling pathways in Prunus mume

Grafting with the dwarf rootstock is an efficient method to control the plant height in fruit production. However, the molecular mechanism is still unclear. Our previous study showed that the plants with Prunus mume rootstock exhibits a considerable reduction in plant height, internode length, and number of nodes compared with Prunus persica rootstock. The present study aimed to investigate the mechanism behind the regulation of plant height by P. mume rootstocks through transcriptome and metabolomic analysis with two grafting combinations, Longyan Mume and Longyan Peach. The findings of the study indicate a significant decrease in BR levels in plants that were grafted onto P. mume rootstocks. Plant hormone signal transduction and brassinolide production metabolism gene expression also changed significantly. Flavonoid levels, amino acid and fatty acid metabolites, and energy metabolism in dwarf plants decreased in the research. The present work observed a notable upregulation of PmLBD3 gene expression in plant specimens that were subjected to grafting onto P. mume rootstocks. Auxin signalling cues promote PmARF3 transcription, which directly controls this upregulation. Through its binding to PmBAS1 and PmSAUR36 gene promoters, PmLBD3 promotes endogenous brassinolide inactivation and inhibits cell proliferation. Auxin signaling and brassinolide levels are linked by this gene. In short, PmLBD3 is a key transcription factor that controls the balance of hormones through the auxin and brassinolide signalling pathways, causing P. mume dwarf to appear.