29.シロイヌナズナの高塩ストレス時における不活性化酵素遺伝子によるジベレリン量調節(口頭発表)

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When exposed to salinity stress, plants retard their growth and become compact in consequence. It was recently reported that bioactive GA levels are decreased in Arabidopsis in response to high-salinity stress, and the resultant increase in DELLA proteins contributes to growth retardation under salt stress conditions (Achard et al., Science 2006). We have reported that overexpression of salinity-responsive DDF1 gene, encoding an AP2 transcription factor of DREB1/CBF subfamily, causes dwarfism mainly through a reduction of GAs by ectopic induction of GA2ox7 gene in transgenic Arabidopsis. Furthermore, the DDF1 overexpressor plants and GA deficient mutants showed increased tolerance to high-salinity stress. These results indicate that a reduction in endogenous GA levels is one of the stress responses in Arabidopsis. We assessed the contribution of the DDF1-GA2ox7 pathway to the reduction in endogenous GA levels under high-salinity stress. Public microarray data (AtGenExpress) and our quantitative RT-PCR results indicate that at least six GA2ox genes (including GA2ox7) are upregulated by high salinity. Furthermore, in both wild type and ga2ox7-2 mutants, bioactive GA_4 levels were similarly decreased under high-salinity, indicating that this decrease occurs in the absence of GA2ox7. These results indicate that, under high-salinity stress, Arabidopsis actively reduces endogenous GA levels not only by transcriptional activation of GA2ox7, but also by inducing multiple GA2ox genes.
2008-10-06

29.シロイヌナズナの高塩ストレス時における不活性化酵素遺伝子によるジベレリン量調節(口頭発表)

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