The role of DET1 in Arabidopsis thaliana seed germination responses on ABA, salt and osmotic stress conditions

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2015-10, 2015, 2016-06, 2016-08
Fernando, Veerahennedige Chamanthi Dilukshi
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Taylor and Francis
Ceylon Journal of Science University of Peradeniya
Plant development is tightly linked to the environment. Environmental signals interact with endogenous hormonal cues, allowing plants to optimize their response to external stress. The plant hormone abscisic acid (ABA) is involved in a variety of stress tolerance mechanisms. These pathways have been widely studied in the model plant Arabidopsis thaliana. In this thesis I investigate the effect of light, ABA, and ABA mediated salt and osmotic stress on Arabidopsis seed germination, examining the role of light signaling component DE-ETIOLATED 1 (DET1) in these mechanisms. DET1 is a negative regulator of the light response promoting transcription factor ELONGATED HYPOCOTYL 5 (HY5). Thus, det1 mutants resemble light grown plants when grown in complete darkness. In this study, det1 mutants showed a variety of different germination phenotypes on control, ABA, and salt/osmotic stress conditions. Germination of det1 was sensitive to ABA but resistant to salt and osmotic stress. det1 ABA sensitive germination appeared to be due to an upregulation of a germination inhibiting transcription factor ABSCISIC ACID INSENSITIVE 5 (ABI5) by HY5. On the other hand, we propose that in salt/osmotic stress conditions, HY5 downregulates another transcription factor, ABSCISIC ACID BINDING FACTOR 3 (ABF3) which inhibits seed germination, thus det1 mutants exhibited resistant germination. In addition, DET1 exhibits genetic interactions with genes in the ABA signalling pathway during development. Both hy5 and abf1 mutants suppressed det1 phenotypes not only during vegetative development but also during germination, suggesting that a pathway whereby DET1 negatively regulates HY5, and HY5 positively regulates ABF1. Moreover components of distinct CULLIN4 DAMAGED DNA BINDING PROTEIN 1 (CUL4-DDB1) E3 ligase complexes both suppressed and enhanced det1 phenotypes. Finally, the det1 rapid water loss phenotype was independent of all genes considered except for ABF1. In conclusion, my PhD research shows DET1 plays an important role in Arabidopsis response to stress conditions and, by acting as a repressor of HY5, has a role in the integration of light and ABA signalling pathways.
Arabidopsis, Seed germination, DET1
Fernando, VC Dilukshi, and Dana F. Schroeder. "Genetic interactions between DET1 and intermediate genes in Arabidopsis ABA signalling." Plant Science 239 (2015): 166-179.
Fernando, V. C., and Dana Schroeder. "Shedding light on plant development: light signalling in the model plant Arabidopsis thaliana." Ceylon Journal of Science 45.1 (2016).
Fernando, V.C. Dilukshi and Schroeder D.F. "Arabidopsis DDB1-CUL4 E3 ligase complexes in det1 salt/osmotic stress resistant germination." Plant Signaling and Behavior (2016) In Press
V. C. Dilukshi Fernando and Dana F. Schroeder (2016). Role of ABA in Arabidopsis Salt, Drought, and Desiccation Tolerance, Abiotic and Biotic Stress in Plants - Recent Advances and Future Perspectives, Dr. Arun Shanker (Ed.), InTech, DOI: 10.5772/61957. Available from: