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

Correspondence to: B. W. Poovaiah¹ Correspondence and requests for materials should be addressed to B.W.P. (Email: poovaiah@wsu.edu).

Abstract

Brassinosteroids are plant-specific steroid hormones^{1, 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 stimuli^{4, 5}. Arabidopsis DWARF1 (DWF1) is responsible for an early step in brassinosteroid biosynthesis that converts 24-methylenecholesterol to campesterol^{6, 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.

MORE ARTICLES LIKE THIS

These links to content published by NPG are automatically generated.