Transcriptome analysis revealed the response of pumpkin to low potassium stress and the role of CmPOT5-like gene in potassium transport

• Two pumpkin varieties C1 and C2 showed different physiological/transcriptome responses to low potassium. • LK inhibits photosynthesis genes (PSI/II, ATPase) and activates lignin genes (POX/PRDX6). • CmPOT5-like enhances K⁺ uptake in Arabidopsis under LK, confirming transport role. • First transcriptome-level study reveals pumpkin's LK adaptation mechanisms. Potassium (K⁺) deficiency significantly impairs pumpkin yield and quality, yet the physiological and molecular responses of pumpkin plants to low-potassium (LK) stress remain underexplored. In this study, we investigated the physiological and transcriptomic responses of two pumpkin varieties, 'CM0091′ (C1, LK-tolerant) and 'CM4602′ (C2, LK-sensitive), under low potassium (LK) and moderate potassium (MK) supply conditions. Our results revealed that the growth was suppressed in both varieties under prolonged LK stress, though to a greater extent in the sensitive C2 line. Transcriptomic analysis revealed distinct responses between C1 and C2 under LK and MK conditions. Under LK stress, 14 genes associated with photosystem I, 11 genes linked to photosystem II, and 2 genes related to F-type ATPase were downregulated, while genes involved in lignin synthesis, such as peroxidase ( POX ) and peroxiredoxin-6 ( PRDX6 ), were upregulated. These molecular changes corresponded with reduced photosynthetic activity in leaves and increased root lignification under LK stress. Additionally, 41 differentially expressed genes associated with K⁺ uptake and transport were identified. Among these, CmPOT5-like ( CmoCh14G009130 ), a key candidate gene for potassium absorption and transport, was characterized. This gene contains a 549 bp open reading frame encoding 182 amino acids and is localized to the plasma membrane, cytoplasm, and nucleus. It is predominantly expressed in roots and significantly upregulated under LK stress. Overexpression of CmPOT5-like in Arabidopsis thaliana significantly enhanced potassium content and accumulation in roots and leaves compared to wild-type plants under LK conditions. This study provides the first comprehensive transcriptomic analysis of pumpkin responses to LK stress and validates the role of a critical potassium transport gene, offering insights for developing potassium-efficient pumpkin varieities.