Temperature is a primary factor affecting the rate of plant development; as the climate warms, extreme temperature events are likely to increasingly affect agriculture. Understanding how to improve crop tolerance to heat stress is a key concern. Wild plants have evolved numerous strategies to tolerate environmental conditions, notably the regulation of root architecture by phytohormones, but the molecular mechanisms of stress resistance are unclear. In this study, we showed that high temperatures could significantly reduce tobacco biomass and change its root architecture, probably through changes in auxin content and distribution. Overexpression of the OsPT8 phosphate transporter enhanced tobacco tolerance to high-temperature stress by changing the root architecture and increased the antioxidant ability. Molecular assays suggested that overexpression of OsPT8 in tobacco significantly increased the expression of auxin synthesis genes NtYUCCA 6, 8 and auxin efflux carriers genes NtPIN 1,2 under high-temperature stress. We also found that the expression levels of auxin response factors NtARF1 and NtARF2 were increased in OsPT8 transgenic tobacco under high-temperature stress, suggesting that OsPT8 regulates auxin signaling in response to high-temperature conditions. Our findings provided new insights into the molecular mechanisms of plant stress signaling and showed that OsPT8 plays a key role in regulating plant tolerance to stress conditions.

Excessive nitrogen fertilizer application in Guizhou’s tobacco-producing regions has degraded soil fertility and reduced leaf quality. Although different transplanting methods strongly influence tobacco growth and productivity, the interactive effects of nitrogen application rates and transplanting methods on rhizosphere soil and tobacco quality remain insufficiently studied. Using flue-cured tobacco cultivar Yunyan 87, a two-factor experiment with three nitrogen application rates and five transplanting methods was conducted. Based on high-throughput sequencing, we systematically analyzed rhizosphere soil physicochemical properties, microbial community characteristics, and their relationships with tobacco leaf quality. The results showed that nitrogen rate and transplanting method significantly affected soil physicochemical properties, and duckbill transplanting combined with low nitrogen application maintained the highest soil organic matter and available potassium contents. Sequencing identified 34 bacterial phyla and 13 fungal phyla. Proteobacteria and Ascomycota were the dominant bacterial and fungal phyla, respectively. Low nitrogen combined with duckbill transplanting significantly enriched nitrogen-cycling taxa such as Nitrospira and Nitrosomonas, and altered the relative abundance of dominant genera including Sphingomonas, Pseudomonas, Botryotrichum, and Mortierella. LEfSe analysis revealed distinct microbial biomarkers among treatments, with Sphingomonas and Sphingomonadaceae significantly enriched under low nitrogen, whereas specific fungal taxa including Agaricomycetes were indicative of certain transplanting regimes. Tobacco leaf chemical components were optimized under the N1T3 treatment (N1: 121.5 kg/hm²; T3: duckbill transplanting), and Pearson correlation analysis revealed close linkages among key rhizosphere microbes, soil properties, and tobacco quality indices. These findings suggest that a nitrogen application rate of 121.5 kg/hm² combined with duckbill transplanting optimizes rhizosphere microbial community structure, enriches N-cycling functional microbiota, regulates key metabolic functions, and improves tobacco leaf quality. This reduced-nitrogen strategy is environmentally sustainable and provides a scientific basis for green and sustainable tobacco cultivation.