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Ca2+/calmodulin is critical for brassinosteroid biosynthesis and plant growth

Nature volume 437, pages 741–745 (2005)Cite this article

Abstract

Brassinosteroids are plant-specific steroid hormones1,2 that have an important role in coupling environmental factors, especially light, with plant growth and development3. How the endogenous brassinosteroids change in response to environmental stimuli is largely unknown. Ca2+/calmodulin has an essential role in sensing and transducing environmental stimuli4,5. Arabidopsis DWARF1 (DWF1) is responsible for an early step in brassinosteroid biosynthesis that converts 24-methylenecholesterol to campesterol6,7. Here we show that DWF1 is a Ca2+/calmodulin-binding protein and this binding is critical for its function. Molecular genetic analysis using site-directed and deletion mutants revealed that loss of calmodulin binding completely abolished the function of DWF1 in planta, whereas partial loss of calmodulin binding resulted in a partial dwarf phenotype in complementation studies. These results provide direct proof that Ca2+/calmodulin-mediated signalling has a critical role in controlling the function of DWF1. Furthermore, we observed that DWF1 orthologues from other plants have a similar Ca2+/calmodulin-binding domain, implying that Ca2+/calmodulin regulation of DWF1 and its homologues is common in plants. These results raise the possibility of producing size-engineered crops by altering the Ca2+/calmodulin-binding property of their DWF1 orthologues.

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Figure 1: Ca 2+ /CaM-binding property of DWF1.
Figure 2: The DWF1 null mutant line Salk_006932 can be rescued by 35S::DWF1.
Figure 3: Loss of CaM binding nullifies DWF1 function.
Figure 4: The C-terminal CaMBD is unique to plant orthologues of DWF1.

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Acknowledgements

This work was partially supported by grants from the National Science Foundation and the United States Department of Agriculture. We thank T. Yang and other members of the laboratory for help and advice during the screening of the cDNA expression library and for discussions during manuscript preparation; M. Zhu for help during fluorescence spectrum analysis; and R. Ketchum and S. Mattinson for help in GC-MS analysis and interpretation. We appreciate the critical reading and helpful suggestions of D. von Wettstein and D. Takezawa.

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  1. Center for Integrated Biotechnology and Department of Horticulture, Washington State University, Washington, 99164-6414, Pullman, USA

    Liqun Du & B. W. Poovaiah

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  1. Liqun Du
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  2. B. W. Poovaiah
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Correspondence to B. W. Poovaiah.

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Reprints and permissions information is available at npg.nature.com/reprintsandpermissions. The authors declare no competing financial interests.

Supplementary information

Supplementary Figure S1

Schematic illustration of endogenous DWF1 and its complementary constructs. (DOC 269 kb)

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Du, L., Poovaiah, B. Ca2+/calmodulin is critical for brassinosteroid biosynthesis and plant growth. Nature 437, 741–745 (2005). https://doi.org/10.1038/nature03973

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