Objective Larix kaempferi is an important tree species for afforestation in Northeast China, with significant ecological and economic value. However, drought stress severely affects its growth and development. The role of ERF transcription factors in the drought stress response of L. kaempferi remains unclear. This study aims to explore the function of the LkERF5 gene from L. kaempferi in the drought stress response of tobacco, thereby providing a theoretical basis for elucidating the drought tolerance mechanism of L. kaempferi and for molecular breeding of stress-resistant forest trees.

Method The LkERF5 gene was cloned from L. kaempferi, and its sequence characteristics were analyzed. Subcellular localization of LkERF5 was determined via transient expression in tobacco. Transcriptional activation activity was assessed using a yeast system. The LkERF5 gene was transformed into tobacco via leaf disk transformation, and the phenotypic and physiological differences between wild-type (WT) and LkERF5-overexpressing transgenic tobacco were analyzed under drought stress.

Result (1) LkERF5 encoded 207 amino acids and contained one AP2/ERF conserved domain. (2) LkERF5 was localized in the nucleus and had transcriptional activation activity. (3) After 14 d of drought treatment, the leaves of WT plants withered or died, while the top leaves of LkERF5 transgenic tobacco remained normal growth state. (4) Under drought stress, LkERF5 transgenic plants showed significantly higher soluble sugar and proline contents, indicating enhanced osmotic regulation. Additionally, chlorophyll content, photosynthetic rate, and water use efficiency were significantly increased in transgenic plants, while stomatal conductance, intercellular CO₂ concentration, and transpiration rate were markedly reduced, suggesting enhanced photosynthesis. Furthermore, superoxide dismutase, peroxidase, and catalase activities were significantly enhanced in transgenic plants, accompanied by reduced reactive oxygen species (ROS) accumulation and malondialdehyde content, indicating reduced cellular damage.

Conclusion Overexpression of LkERF5 in tobacco enhances drought tolerance by increasing osmotic adjustment substances, improving photosynthetic efficiency, and scavenging ROS content. This study not only provides critical insights into the functional characterization of LkERF5 in L. kaempferi, but also identifies valuable candidate genetic resources for the improvement of L. kaempferi germplasm.