Arabodopisis ChyB And DREB2A Genes Improved Transgenic Tobacco Abiotic Stress Tolerance

Abiotic stresses such as strong sunlight, high temperature, drought and salinityare principal problems for agriculture and major reasons that account for crop yieldreduction. Under such conditions, plant often produces a lot of reactive oxygenspecies (ROS) that cause damage. During their long history of evolution, plants haveevolved a variety of molecular and biochemical mechanisms to adapt to these adverseconditions.The dehydration-responsive element (DRE)/CRT (C-repeat) containing theconserved sequence A/GCCGAC and was identified as a cis-element located inpromoter region of genes involved in abiotic stress tolerance. In1997, Stocking andhis colleagues isolated a cDNA encoding a DRE/CRT binding protein,CBF1/DREB1B from Arabidopsis, by the yeast one-hybrid screening. Since then,many DREB family genes were isolated from a variety of plants and their productsspecifically bind to DRE/CRT to activate transcription of genes that confer plant withtolerance to abiotic stress such as drought, salt, and low temperature.In order to investigate the function of DREB2ACA in plant salt-tolerance reactionand thus to explore its application value in genetic engineering. DREB2ACA wascloned using SOE-PCR, and was constructed in plant expression vector driven byrd29A promoter. Tobacco plants were genetically transformed with the vector.Integration and expression of the gene was confirmed using molecular analysis.Compared to the control, transgenic lines had higher photosynthesis pigments,enhanced photosynthesis rate and lower MDA level under salt condition.Salt-inducible expression of DREB2ACA enhanced transcripts of tobacco LEANtRED10A. Under salt stress, the transgenic lines maintained higher SOD, PODactivity, higher proline concentration. All these results demonstrate that DREB2ACAis probably a promising candidate gene for drought improvement in crops.Carotenoids are essential for photosynthesis and photoprotection in plant life. Inorder to study the protective role of zeaxanthin under drought stress, we increased thecapacity for its accumulation in tobacco by over-expression of Arabidopsis β-carotenehydroxylase chyB gene. This manipulation leads to a2-4fold increase of xanthophyllscycle pigments. Under high-light condition, the transformants converted moreβ-carotene into zeaxanthin compared to the controls. The enhancement of zeaxanthinincreased the total antioxidant capacity in lipid phase and made plants more tolerant todrought stress, as shown by less leaf necrosis, reduced lipid peroxidation and enhanced photosynthesis rate. The function of the gene in drought tolerance wasexplored and discussed. We conclude that genetic manipulation of chyB gene maypresent a powerful method in the production of drought-tolerant crops.