Abstract
The role of brassinosteroids in plant growth and development has been well-characterized in a number of plant species. However, very little is known about the role of brassinosteroids in maize. Map-based cloning of a severe dwarf mutant in maize revealed a nonsense mutation in an ortholog of a brassinosteroid C-6 oxidase, termed brd1, the gene encoding the enzyme that catalyzes the final steps of brassinosteroid synthesis. Homozygous brd1–m1 maize plants have essentially no internode elongation and exhibit no etiolation response when germinated in the dark. These phenotypes could be rescued by exogenous application of brassinolide, confirming the molecular defect in the maize brd1-m1 mutant. The brd1-m1 mutant plants also display alterations in leaf and floral morphology. The meristem is not altered in size but there is evidence for differences in the cellular structure of several tissues. The isolation of a maize mutant defective in brassinosteroid synthesis will provide opportunities for the analysis of the role of brassinosteroids in this important crop system.
Highlights
Manipulation of plant height and growth habits to adjust plant architecture may allow for improved agronomic production in crop plants, from biofuel applications to more efficient use of available resources [1]
Maize brd1 is a homolog encoding brC-6 oxidase, an enzyme that controls the last steps of brassinosteroid biosynthesis
A mutation in GRMZM2G103773, a maize homolog for brC6 oxidase that is involved in the BR biosynthesis
Summary
Manipulation of plant height and growth habits to adjust plant architecture may allow for improved agronomic production in crop plants, from biofuel applications to more efficient use of available resources [1]. Gibberellins (GAs), a large group of cyclic diterpene compounds that promote stem elongation, and brassinosteroids (BRs), commonly occurring steroid hormones that regulate multiple aspects of plant growth and development, are two classes of hormones that alter plant architecture when aberrations occur in their biosynthesis or signaling pathways [1,2]. Mutations in GA-related genes are responsible for the semidwarf phenotypes associated with the green revolution [3] and dwarf or semi-dwarf phenotypes have potential as targets for further agronomic improvement [1]. Consistent with the main function of BRs in promoting cell elongation, mutants deficient in brassinosteroid biosynthesis and signaling display various levels of dwarfism [1]. Relatively little is known about the specific functional role of brassinosteroids in maize [1]
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