A comparative study on the protective role of trehalose and LEA proteins against abiotic stresses in transgenic Chinese cabbage (Brassica campestris) overexpressing CaLEA or otsA

Abstract

Trehalose and LEA proteins, representative low MW chemicals that are synthesized under dehydration, are known to protect plants from drought stress. To compare their effectiveness on enhancing tolerance against various abiotic stresses, we generated transgenic Chinese cabbage plants overexpressing E. coli trehalose-6-phosphate synthase gene (otsA) or hot pepper (Capsicum annuum) LEA protein gene (CaLEA). Both transgenic plants exhibited altered phenotype including stunted growth and aberrant root development. When subjected to drought, salt or heat stress, these plants showed remarkably improved tolerance against those stresses compared with nontransformants. After dehydration treatment, leaf turgidity and fresh weight was better maintained in both transgenic plants. CaLEA-plants performed somewhat better under dehydrated condition. When treated with 250 mM NaCl, both otsA-plants and CaLEA-plants remained equally healthier than nontransformants in maintaining leaf turgidity and delaying necrosis. Furthermore, leaf Chl content and Fv/Fm was maintained considerably higher in both transgenic plants than nontransformants. After heat-treatment at 45degreesC, both transgenic plants appeared much less damaged in external shape and PSII function, but LEA proteins were more protective. Our results indicate that although both trehalose and LEA proteins are effective in protecting plants against various abiotic stresses, LEA proteins seem to be more promising in generating stress-tolerant transgenic plants.