Transcriptomic and physiological insights into auxin-mediated root growth and potassium uptake in tobacco under low-potassium stress

BACKGROUND: Improving potassium uptake efficiency in plants is crucial for agricultural production. Auxin is a key plant hormone that promotes root growth and enhances the ability of plants to absorb and accumulate mineral nutrients. To investigate the role of auxins in root growth and potassium uptake mechanisms under low-potassium stress, we used tobacco as a model plant and conducted hydroponic experiments. RESULTS: Low-potassium stress significantly impairs root development and potassium uptake in tobacco plants. Under these conditions, exogenous Indole acetic acid (IAA) enhanced root development and increased potassium uptake, whereas N-1-naphthylphthalamic acid (NPA) inhibited root growth and adversely affected potassium absorption and retention. Transcriptome sequencing under low-potassium conditions identified 8,381 differentially expressed genes (DEGs) between the two different treatment groups that were primarily enriched in pathways related to photosynthesis-antenna proteins, photosynthesis, plant hormone signal transduction, and the MAPK signaling pathway. Analysis of the DEGs associated with auxin signaling, potassium ion channels, transporters, and transcription factors revealed several key genes involved in low-potassium stress response, including KUP6, IAA14, ARF16, PIN1, SKOR, NPF7.3, and AP2/ERF. Notably, KUP6 was upregulated following IAA treatment and downregulated by NPA, indicating that this potassium ion transporter gene plays a crucial role in the auxin-mediated alleviation of low potassium stress in tobacco, which is likely linked to endogenous auxin levels. CONCLUSIONS: Our study revealed that potassium deficiency impairs root development and uptake in tobacco and that auxin is critical in mitigating this stress. This study highlights the regulatory function of auxin in enhancing root growth and potassium absorption under low potassium conditions, offering insights into the molecular mechanisms of potassium stress response.