Spatiotemporal localization of jasmonate in the regulation of fruit set in tomato

Tomato (Solanum lycopersicum) is a globally important crop, typically requiring pollination for fruit set. Seedless fruit production—fruit set without pollination (parthenocarpy)—is a desirable trait for horticulture, though its molecular mechanisms are not fully understood. Research on tomato fruit set has largely focused on phytohormones like auxin and gibberellins (GAs), while the role of jasmonic acid (JA) remains unclear. Here, we identified a novel seedless mutant, Sldad1 (Solanum lycopersicum defective in anther dehiscence1), with a mutation in JA biosynthesis induced by ethyl methanesulfonate (EMS) mutagenesis in the ‘Micro-Tom’ background. SlDAD1 was specifically transcribed in the stamen filament, particularly two days before anthesis, with JA levels correlating to its transcript abundance, as visualized by imaging mass spectrometry. Notably, JA also accumulated in the ovary and ovule before anthesis. Sldad1 produced seedless fruit without any manual pollination or emasculation (untouched) and seeded fruit via self-pollination. The mutant showed increased cell expansion, elevated GA levels, and higher GA20ox3 gene transcripts, while GA biosynthesis inhibition treatment suppressed Sldad1-induced fruit set. Overall, our findings suggest that JA synthesized in the filament accumulates in the ovule before anthesis, thereby preventing tomato fruit set, at least in part, through the modulation of GA metabolism.