Stu-miR393-5p-StTIR1A-StPLC2 module regulates the development of adventitious and lateral roots of potato.

key messageStu-miR393-5p and StTIR1A modulate adventitious root length, thereby directly affecting plant height of potato. An interaction occurs between the StTIR1A and StPLC2 proteins. Potato (Solanum tuberosum L.), as the world's fourth-largest food crop, is frequently subjected to abiotic stresses-notably drought and high soil salinity-which impair growth and reduce yields. Modifying root architecture represents a promising strategy to enhance environmental adaptability. However, due to its shallow-rooted phenotype, research on the structural regulation of potato root systems remains limited. This study demonstrates that Stu-miR393-5p modulates plant growth through dual regulation of root system architecture and auxin homeostasis, primarily by altering adventitious root length and lateral root number. Dual-luciferase and GUS reporter assays confirmed direct cleavage of StTIR1A mRNAs by Stu-miR393-5p. StTIR1A expression was post-transcriptionally repressed by Stu-miR393-5p. Modification of the StTIR1A gene altered adventitious root development, lateral root number, and root auxin content in potato plants. We confirmed that StTIR1A interacts with StPLC2, StRACK, and StSINAT2 via yeast two-hybrid, bimolecular fluorescence complementation, and split-luciferase complementation assays. Analysis of the expression of StYUCCA3, StGH3.4, and StPIN1 in StTIR1A transgenic lines demonstrated that the Stu-miR393-5p-StTIR1A module participates in auxin signaling transduction and modulates root morphogenesis. Integrating these results with the known function of PLC2 in auxin homeostasis, we propose a coherent Stu-miR393-5p-StTIR1A-StPLC2 module. Collectively, our findings establish that this module regulates IAA signaling to shape root architecture, thereby opening a new avenue for research on improving potato root systems.