NATARAJA KARABA, N.Pruthvi, V.2017-02-272017-02-272013-03-19Th-10468http://krishikosh.egranth.ac.in/handle/1/5810002674Drought, temperature extremes and salinity are the most common abiotic stresses, adversely affecting plant growth and productivity. Plants activate stress signalling pathways, biochemical and physiological processes necessary for stress adaptation upon stress induction. Although stress tolerance is governed by multiple traits, a few traits play a major role in adaptation. Under drought, traits linked to water mining and water conservation, water use efficiency and cellular tolerance (CT) to desiccation are considered to be relevant. In this study, attempts have been made to improve CT in drought hardy crop, peanut (Arachis hypogaea, cv. TMV2) and susceptible crop, sunflower (Helianthus annuus, IB20) by coexpressing stress-responsive transcription factors (TFs, namely, AtDREB2A, AtHB7 and AtABF3), the major proteins associated with gene expression. Transgenic crops showed increased tolerance to drought, salinity and oxidative stresses compared to wild type. Simultaneous expression of three TFs induced the expression of various stress responsive genes including detoxifying enzymes, protein kinase, RD29a, LEA and chaperons indicating that co-expression of TFs can be a good strategy to improve stress tolerance by activating multiple pathways. Attempts have also been made to prospect candidate TFs from drought hardy crop, peanut, and three different TFs, namely, AhZinc finger, AhBTF3 and AhNFYA7 were cloned from cDNA and functionally validated under different stresses by over expression in model plant, tobacco. AhZinc finger overexpression resulted in an increased expression of detoxifying enzymes leading to enhanced tolerance to heavy metal stress. AhBTF3 transgenic plants showed better phenotype under mannitol- and NaCl-induced stresses. Similarly, AhNFYA7 transgenic plants exhibited increased tolerance under DTT- and tunicamycin-induced ER stresses. The study demonstrated that the three genes cloned have relevance in improving cellular tolerance under stressful conditions.ennullThesis