Plant growth regulation useful for plant production in arid environment

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We isolated seven Arabidopsis mutants (mizu-kussei : miz) defective in root hydrotropism. We characterized their phenotypes and identified genes responsible for the mutations of miz1 and miz6. Roots of both miz1 and miz6 showed impaired hydrotropism, but their gravitropism, elongation growth and morphological feature were normal. These results suggest that the pathway inducing hydrotropism is independent of gravitropism. MIZ1 phenotype resulted from a single recessive mutation, which encoded a novel protein containing a domain (the MIZ domain) that was highly conserved among terrestrial plants. We hypothesized that MIZ1 evolved to play an important role in adaptation to terrestrial life. In addition, a pMIZ1::GEIS fusion gene was strongly expressed in columella cells of the root cap but not in the elongation zone, suggesting that MIZ1 functions in the early phase of the hydrotropic response. We found that auxin response is indispensable for both hydrotropism and gravitropism, but mecha … More nisms for auxin redistribution differ between hydrotropism and gravitropism in Arabidopsis roots.A variety of wheat, Hong Mang Mai, exhibits tolerance to deep-sowing conditions by extreme elongation of the first internodes in soil. To exert this response, the first internodes of Hong Mang Mai possessed greater ability to produce cells, compared to other varieties. It was revealed that gibberellin plays roles in both cell elongation and cell division of the internodes. However, extraordinary elongation of the first internodes of Hong Mang Mai occurred due to cell division rather than cell elongation. Based on these results, we are now studying molecular mechanisms for the deep-sowing tolerance of Hong Mang Mai.Plants respond to gravity for controlling their growth orientation. We found that gravisensing is required for circumnutation and winding response in morning glory and that glycine-rich protein (CsGRP1) and auxin-mediated transcription (CsARF2 and CsARF5) play roles in the gravity regulation of peg formation in cucumber seedlings. Less