<scp> <i>StLAX5</i> </scp> regulates stolon initiation to control the tuber number and productivity of potato

The stolon, whose subapical swelling produces the edible tuber and thus determines the ultimate yield, is one of the most striking features of potato. However, the initiation of this critical organ is a complex process whose regulatory mechanisms remain elusive. This study demonstrated that StLAX5, an auxin influx carrier, is a key determinant of stolon and tuber number in potato. Compared with wild-type (WT) plants, StLAX5-knockout (KO) lines showed a significant reduction in stolon and tuber number, while StLAX5-overexpression (OE) lines exhibited a marked increase in these traits. Compared with the WT plants, StLAX5-KO lines had fewer lateral stolon primordia and lower indole-3-acetic acid (IAA) content, whereas StLAX5-OE lines showed increases in both indices. This indicates that StLAX5-mediated auxin accumulation is critical for stolon initiation in potato. In conclusion, StLAX5 regulates stolon emergence by modulating IAA content, and node density via internode elongation, thereby ultimately determining potato tuber number and productivity.