Heterologous Overexpression of NtNACa from Narcissus tazetta L. var. chinensis ‘Yunxiang’ Enhances Drought and Salt Stress Resistance in Arabidopsis thaliana

Background/Objectives: NAC transcription factors are key regulators of stress responses, yet their roles in Narcissus tazetta L. var. chinensis remain uncharacterized. This study aimed to isolate and functionally analyze NtNACa, a NAC gene from the ‘Yunxiang’ narcissus variety, to evaluate its potential in enhancing abiotic stress tolerance. Methods: NtNACa was cloned and its expression pattern under heat, salt, and ABA treatments was assessed via qRT-PCR. Subcellular localization was determined using GFP fusion in tobacco. NtNACa was overexpressed in Arabidopsis thaliana through floral dip transformation, and transgenic lines were subjected to NaCl, ABA, and drought stress assays. Results: The results showed that NtNACa has high homology with monocot NAC family members and possesses typical NAC transcription factor features. Further analyses revealed that NtNACa localizes to the nucleus, and tissue-specific expression analysis indicated that it is highly expressed in leaves, followed by roots and bulbs. The transcriptional expression of NtNACa is differentially regulated in response to 100 mM NaCl, 100 μM ABA, and 50 °C temperature stress. Overexpression of NtNACa in A. thaliana produced transgenic lines with significantly higher germination rates under ABA and NaCl treatments. Soil-grown transgenic A. thaliana plants overexpressing NtNACa showed markedly increased drought stress. Moreover, NtNACa confers drought resilience by coordinately suppressing oxidative damage (via reduced O2−· production rate and MDA accumulation and elevated AtCAT2 expression), enhancing osmotic adjustment (through AtP5CR-mediated proline biosynthesis), and activating core stress-signaling components such as AtRD29A and AtSnRK2.4. Conclusions: Taken together, these results indicate that heterologous overexpression of NtNACa from ‘Yunxiang’ (N. tazetta) confers enhanced drought and salt tolerance in A. thaliana.