Temperature Perception Regulates Seed Germination in Solanum nigrum via Phytohormone Signaling Pathways

Black nightshade (Solanum nigrum L.) is a highly invasive weed in agricultural systems, primarily dispersed by seeds. Its germination is regulated by temperature, which varies among populations. We investigated the germination responses to temperature in two S. nigrum populations (XJ1600 and XJ1633) and identified eight putative candidate genes: GA20ox1, GA3ox1, GA2ox1, NCED9, CYP707A2, SPT, PIF1, and ABI5. These genes are involved in the phytohormone signaling pathway. Under low-temperature conditions, SPT likely perceives cold signals, promoting germination by up-regulating GA20ox1 and CYP707A2 while suppressing GA2ox1, thus potentially increasing bioactive GAs and reducing ABA levels. Under high-temperature conditions, PIFs likely perceive the heat signal. Through regulation mediated by the known negative regulator SOMNUS (SOM), NCED9 and GA2ox1 were up-regulated, while GA3ox1 was down-regulated, which could collectively modulate seed germination by altering ABA and GA levels. This study clarifies how temperature regulates S. nigrum seed germination through integrated hormonal and genetic mechanisms. This understanding directly supports the development of predictive models for weed emergence and informs the design of sustainable control strategies.