Constitutive expression of a group 3 LEA protein from Medicago falcata (MfLEA3) increases cold and drought tolerance in transgenic tobacco.

KEY MESSAGE: MfLEA3 is involved in protection of catalase activity and confers multiple abiotic stress tolerance. Late embryogenesis abundant (LEA) proteins are involved in plant growth, development and abiotic stress tolerance. A member of group 3 LEA proteins from Medicago sativa subsp. falcata (L.) Arcang, MfLEA3, was investigated in the study. MfLEA3 transcript was induced in response to cold, dehydration, and abscisic acid (ABA), while the cold-induced transcript of MfLEA3 was blocked by pretreatment with inhibitor of ABA synthesis. Constitutive expression of MfLEA3 led to enhanced tolerance to cold, drought, and high-light stress in transgenic tobacco plants. Compared to accumulated reactive oxygen species (ROS) in the wild-type in response to treatments with low temperature, drought, and high light, ROS were not accumulated in transgenic plants. Superoxide dismutase, catalase (CAT), and ascorbate-peroxidase activities were increased in all plants after treatments with the above stresses, while higher CAT activity was maintained in transgenic plants compared with wild-type. However, transcript level of CAT-encoding genes including CAT1, CAT2, and CAT3 showed no significant difference between transgenic plants and wild-type, indicating that the higher CAT activity was not associated with its gene expression. ABA sensitivity and transcripts of several ABA and stress-responsive genes showed no difference between transgenic plant and wild-type, indicating that ABA signaling was not affected by constitutive expression of MfLEA3. The results suggest that MfLEA3 may be involved in the protection of CAT activity and confers multiple abiotic stress tolerance.