The germin-like protein gene Mdip1 was introduced into tomato line Ailsa Craig via Agrobacterium-mediated method. Transgenic lines were confirmed for integration into the tomato genome using PCR, Southern blot hybridization. One to three copies of the transgene were integrated into the tomato nuclear genome. Transcription of Mdip1 in various transgenic lines was determined using real-time PCR. Performance test of resistance analyses to chilling stress with T1 generation transgenic tomato lines showed that the transgenic lines exhibited lighter symptoms of chilling injury and kept higher values of biomass accumulation and chlorophyll content than those of non-transformed plants. The resistance levels were related to expression levels of the transgene compared with wild-type plants, and the contents of AsA and AsA/DHA in both normal and low-temperature conditions were increased, while the H2O2 and MDA content were decreased in the transgenic plants. Meantime, the contents of GSH and GSH/GSSG and GalLDH activity were also increased in the overexpression plants. Based on these results, it can be concluded that Mdip1 may play a pivotal role in increasing tomato tolerance against chilling stress by increasing redox level and lowering H2O2 and lipid peroxidation accumulation.

The widely present symbiotic association between arbuscular mycorrhizal fungi (AMF) and plant roots contributes considerably to improve plant growth, nutrient uptake and stress responses. The present study addressed the potential of AM fungus Funneliformis mosseae in the alleviation of chilling stress for cucumber seedlings. The results showed that the AMF-inoculated cucumber seedlings had significant higher fresh weight and dry weight than non-AMF inoculated control plants under both normal (25/15 degrees C) and low temperature (15/10 degrees C) treatment. Under chilling stress, AMF inoculation significantly improved the content of related secondary metabolites including phenols, flavonoids, lignin, DPPH activity and phenolic compounds compared with the non-AMF control. Furthermore, large increments were observed in a number of enzymatic activities related to secondary metabolism and antioxidant system in AMF-inoculated seedlings under low temperature, such as glucose-6-phosphate dehydrogenase (G6PDH), shikimate dehydrogenase (SKDH), phenylalanine ammonia-lyase (PAL), cinnamyl alcohol dehydrogenase (CAD), polyphenol oxidase (PPO), guaiacol peroxidase (G-POD), caffeic acid peroxidase.(CA-POD) and chlorogenic acid peroxidase (CGA-POD). As well, the expression of stress-related marker genes was enhanced in AMF-inoculated seedlings in comparison with the non-AMF control. Furthermore, AMF symbiosis decreased hydrogen peroxide (H2O2) content under low temperature. Taken together, these results indicated that the enhanced secondary metabolism and integrated transcriptional regulation might play a crucial role in AMF-mediated alleviation of chilling stress in cucumber. (C) 2013 Elsevier B.V. All rights reserved.

The mitochondrial uncoupling protein genes improve plant stress tolerance by minimizing oxidative damage. However, the underlying mechanism of redox homeostasis and antioxidant signaling associated with reactive oxygen species (ROS) accumulation remained poorly understood. We introduced LeUCP gene into tomato line Ailsa Craig via Agrobacterium-mediated method. Transgenic lines were confirmed for integration into the tomato genome using PCR and Southern blot hybridization. One to three copies of the transgene were integrated into the tomato nuclear genome. Transcription of LeUCP in various transgenic lines was determined using real-time PCR. Transgenic tomato overexpressing LeUCP showed higher growth rate, chlorophyll content, maximum photochemical efficiency of PSII (Fv/Fm), photochemical quenching coefficient (qP) and electron transport rate (ETR), increased contents of AsA and proline, higher AsA/DHA ratio and GalLDH activity, reduced ROS accumulation, and enhanced heat stress tolerance compared with the control plants. The transgenic tomato plants also exhibited significant increases in tolerance against the necrotrophic fungus Botrytis cinerea. Taken together, our results suggest that LeUCP may play a pivotal role in controlling a broad range of abiotic and biotic stresses in plants by increasing redox level and antioxidant capacity, elevating electron transport rate, lowering H2O2 and lipid peroxidation accumulation.