Functional Study on the Regulation of Adventitious Root Formation by Serine Acetyltransferase 4 in Peach Rootstock ‘GF 677’

Objective To investigate the molecular characteristics and biological function of PpSAT4 (a serine acetyltransferase-encoding gene) in adventitious root formation, and explore its potential as a candidate gene for improving the rooting ability of difficult-to-root peach rootstocks via molecular breeding. Methods PpSAT4 was identified from the adventitious root transcriptome of the peach rootstock ‘GF677’. Its function in adventitious root formation was validated through heterologous overexpression in Prunus salicina and Arabidopsis thaliana. Results PpSAT4 encodes a 287-amino-acid protein, with a predicted molecular weight of 30.49 kDa and an isoelectric point (pI) of 6.70. Promoter sequence analysis identified multiple cis-acting regulatory elements, including light-responsive, auxin-responsive (e.g., TGA-element) and gibberellin-responsive (e.g., P-box) elements, indicating that PpSAT4 expression may be regulated by key plant hormones and environmental signals during adventitious root initiation. Stable PpSAT4 -overexpressing transgenic lines were successfully obtained in both species. In Prunus salicina , PpSAT4 overexpression significantly promoted adventitious root formation (increased root length, root surface area, root diameter, root volume and root tip number) and enhanced root peroxidase (POD) and superoxide dismutase (SOD) activities. Consistent results were observed in transgenic Arabidopsis , which showed longer primary roots, higher lateral root density, and elevated POD and SOD activities. These results confirm the conserved pro-rooting function of PpSAT4 in peach. Conclusion PpSAT4 positively regulates adventitious root formation, likely by modulating redox homeostasis. It is a promising target for improving rooting capacity of difficult-to-root peach rootstocks through genetic engineering.