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Brassinosteroids Are Master Regulators of Gibberellin Biosynthesis in Arabidopsis

2015; Oxford University Press; Volume: 27; Issue: 8 Linguagem: Inglês

10.1105/tpc.15.00433

1532-298X

Simon Josef Unterholzner, Wilfried Rozhon, Michael Papacek, Jennifer Ciomas, Theodor Lange, Karl Kugler, Klaus Mayer, Tobias Sieberer, Brigitte Poppenberger,

Plant Stress Responses and Tolerance

Plant growth and development are highly regulated processes that are coordinated by hormones including the brassinosteroids (BRs), a group of steroids with structural similarity to steroid hormones of mammals. Although it is well understood how BRs are produced and how their signals are transduced, BR targets, which directly confer the hormone's growth-promoting effects, have remained largely elusive. Here, we show that BRs regulate the biosynthesis of gibberellins (GAs), another class of growth-promoting hormones, in Arabidopsis thaliana. We reveal that Arabidopsis mutants deficient in BR signaling are severely impaired in the production of bioactive GA, which is correlated with defective GA biosynthetic gene expression. Expression of the key GA biosynthesis gene GA20ox1 in the BR signaling mutant bri1-301 rescues many of its developmental defects. We provide evidence that supports a model in which the BR-regulated transcription factor BES1 binds to a regulatory element in promoters of GA biosynthesis genes in a BR-induced manner to control their expression. In summary, our study underscores a role of BRs as master regulators of GA biosynthesis and shows that this function is of major relevance for the growth and development of vascular plants.