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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. [ABSTRACT FROM AUTHOR]

Seashore paspalum (Paspalum vaginatum Swartz) is a commonly used warm-season turfgrass with superior salt tolerance. Low temperature is one of the major abiotic stresses limiting its growth and plantation regions. A protocol for ethyl methane sulphonate (EMS) induced mutations from embryogenic callus and selection of seashore paspalum mutant line with enhanced cold tolerance was established in the study. Treatment of embryogenic callus with 5 h of 0.8% EMS resulted in an approximate 50% survival rate of callus, which was used for inducing mutations from embryogenic callus of seashore paspalum. One mutant line (A6) with enhanced cold tolerance was selected and identified from about 10,000 regenerated plantlets. A6 had lower TEL50 (the temperature resulted in 50% electrolyte leakage) and higher survival rate than its wild type (WT) plants after 7 days of cold acclimation. Antioxidant defense system was responsive to low temperature in both genotypes, while higher CAT activity was maintained in A6 than in WT after 3 days of cold treatment. Among four DREB1/CBF genes induced by cold treatment, higher levels of DREB1A, DREB1D, DREB1E transcripts were observed in A6 than in WT. Free amino acids concentrations in response to cold treatment also showed difference between A6 and WT. The results suggest that the response of DREB1/CBFs expression, CAT activity, and free amino acids concentrations to cold is differentially altered in A6 compared with WT, which is associated with the enhanced cold tolerance in A6. Key message: A mutant line with enhanced cold tolerance was selected by EMS mutagenesis in seashore paspalum. It had higher catalase activity and DREB1/CBFs transcripts with altered free amino acids than WT. [ABSTRACT FROM AUTHOR]

Seashore paspalum (Paspalum vaginatum O. Swartz) is an important warm-season turfgrass with great salinity tolerance. Based on establishment of embryogenic callus induction and regeneration from different mature seeds of ‘Sea Spray’, an Agrobacterium tumefaciens-mediated transformation was established and optimized in this study. Three clones of callus were selected for examining transformation conditions using Agrobacterium tumefaciens strain AGL1 carrying the binary vector pCAMBIA1305.2, containing β-glucuronidase (GUS) as a reporter gene and hygromycin phosphotransferase (HPT) as a selective marker gene. The results showed that a high transient transformation efficiency was observed by using Agrobacterium concentration of OD600 = 0.6, 5 min of sonication treatment during Agrobacterium infection, and 2 d of co-cultivation. By using the optimized transformation conditions, transgenic seashore paspalum plants were obtained. PCR and Southern blot analysis showed that T-DNA was integrated into the genomes of seashore paspalum. GUS staining experiments showed that the GUS gene was expressed in transgenic plants. Our results suggested that the transformation protocol will provide an effective tool for breeding of seashore paspalum in the future. [ABSTRACT FROM AUTHOR]