While high-temperature stress severely inhibits the growth, development, and tuberization of potatoes (Solanum tuberosum L.), moderate high temperatures can trigger thermomorphogenesis. However, the molecular mechanisms underlying thermomorphogenesis in potato remain largely elusive. In this study, we identified a heat-responsive, nucleus-plastid shuttling transcriptional activator, StHEMERA (StHMR), whose nuclear translocation was enhanced under high-temperature conditions. Transgenic analyses revealed that the high-temperature induced increase in plant height and cell elongation in potato depends on the function of StHMR. The StHMR-silenced lines displayed a phenotype insensitive to elevated temperatures. Biochemical evidence further revealed that StHMR forms a regulatory module with PHYTOCHROME INTERACTING FACTOR 4 (StPIF4), a potato homolog of the central Arabidopsis thermosensory. StPIF4 is indispensable for high-temperature-induced stem elongation and directly binds the promoters of the auxin biosynthesis gene YUCCA8 (StYUC8) and the cell-elongation gene α-EXPANSION A8 (StEXPA8). StPIF4 regulates cell elongation under high-temperature conditions by binding to E-box elements within the promoters of these genes. Notably, StHMR functions as a transcriptional co-activator that enhances the ability of StPIF4 to activate the transcription of StYUC8, especially under heat conditions. Collectively, this study characterizes the StHMR-StPIF4 module as a key molecular unit of potato thermomorphogenesis and highlights its potential relevance to tuber formation, providing promising molecular targets for breeding heat-tolerant potato varieties.

Soil salinization is one of the most prominent abiotic stresses affecting agricultural production. As the third most significant staple crop, the potato exhibits heightened sensitivity to salt stress. Alternative polyadenylation (APA) is a key regulator of gene expression, significantly impacting plant growth and stress response. However, the role of APA in response to salt stress remains elusive in potato, as genetic resources for salt-tolerant potatoes are limited. In this study, germplasms of nine salt-sensitive and seven salt-tolerant accessions were screened, respectively. Salt-tolerant germplasms exhibited superior ROS scavenging capabilities and ionic balance compared to salt-sensitive germplasms. This study characterized APA events in leaves and roots of Morocco 1 (salt-tolerant) and Qingshu 9 (salt-sensitive) under control and salt stress using TAIL-seq. Salt stress induced global APA dynamics in potato. A total of 1831 and 4235 APA genes were identified in the leaves and roots of Qingshu 9, respectively. In contrast, Morocco 1 exhibited only 559 and 2696 APA genes in its leaves and roots, respectively. APA led to an average extension of the 3’ UTR of most genes by 25 bp. Moreover, five candidate genes potentially responsive to salt stress via APA were identified. In summary, our results illustrate that APA is significant for regulating gene expression under salt stress, providing new perspectives for studying salt tolerance in potato.