Abstract
Hypocotyl growth occurs as a result of an interaction between environmental factors and endogenous phytohormones. In Arabidopsis, high temperature promotes auxin synthesis to increase hypocotyl growth. We previously showed that exogenously provided auxin stimulates expression of the brassinosteroid (BR) biosynthetic gene DWARF4. To determine whether temperature-induced hypocotyl elongation depends on BR biosynthesis, we examined the morphological responses to high temperature and the expression pattern of DWF4pro:GUS in different genetic backgrounds, which are as follows: Ws-2 wild-type, iaa19/msg2, bri1-5, and dwf7-1. In contrast to the wild-type, growth of the three genotypes at 29°C did not significantly increase hypocotyl length; whereas, with the exception of iaa19/msg2, the roots were elongated. These results confirm that BR biosynthesis and signaling pathways are required for hypocotyl growth at high temperature. Furthermore, a GUS histochemical assay revealed that a temperature of 29°C greatly increased DWF4pro:GUS expression in the shoot and root tips compared to a temperature of 22°C. Quantitative measurements of GUS activity in DWF4pro:GUS revealed that growth at 29°C is similar to the level of growth after addition of 100 nM IAA to the medium. Our results suggest that temperature-dependent synthesis of free auxin stimulates BR biosynthesis, particularly via the key biosynthetic gene DWF4, and that the BRs thus synthesized are involved in hypocotyl growth at high temperature.
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Acknowledgments
This research was supported in part by grants from the Next-Generation BioGreen 21 Program (Plant Molecular Breeding Center No. PJ008051) and the Cooperative Research Program for Agriculture Science & Technology Development (Project No. PJ906910), Rural Development Administration, Republic of Korea; the Technology Development Program (110033-5) for Agriculture and Forestry, Ministry for Food, Agriculture, Forestry and Fisheries, Republic of Korea, and the Basic Science Research Program through the National Research Foundation of Korea (NRF) as funded by the Ministry of Education, Science and Technology (2010-0012736) (to SC); and the BK21 Research Fellowships funded by the Ministry of Education, Science, and Technology of the Korean Government (to PM) S.D.G.
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Maharjan, P.M., Choe, S. High Temperature Stimulates DWARF4 (DWF4) Expression to Increase Hypocotyl Elongation in Arabidopsis . J. Plant Biol. 54, 425–429 (2011). https://doi.org/10.1007/s12374-011-9183-6
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DOI: https://doi.org/10.1007/s12374-011-9183-6