Abstract
The “green revolution” gene gibberellin oxidase contributes to the semidwarf phenotype, improving product and lodging resistance. Dissecting the function of GA biosynthetic genes would be helpful for dwarf maize breeding. In this study, we edited the maize GA20ox3 gene and generated semidwarf maize plants using CRISPR/Cas9 technology. Application of exogenous gibberellin can recover the dwarf phenotype, indicating that the mutants are gibberellin deficient. The contents of GA12 and GA53 were elevated in the mutants due to the disruption of GA20 oxidase, whereas the contents of other GA precursors (GA15, GA24, GA9, GA44, and GA20) were decreased in the mutants, and the accumulation of bioactive GA1 and GA4 was also decreased, contributing to the semidwarf phenotype. Transgene-free dwarf maize was selected from T2-generation plants and might be useful for maize breeding in the future.
Highlights
Gibberellin (GA) is an important hormone in plants and plays essential roles in plant growth and development, including embryogenesis, seed germination, stem elongation, and flowering (Yamaguchi and Kamiya, 2000; Binenbaum et al, 2018)
Dwarf8 gene has Generation of Transgene-Free Semidwarf Maize been identified as an orthologue of the GAI gene and been targeted by selection (Peng et al, 1999; Andersen et al, 2005)
Gene-edited “transgene-free” dwarf maize plants were generated, which might be useful for maize breeding in the future
Summary
Gibberellin (GA) is an important hormone in plants and plays essential roles in plant growth and development, including embryogenesis, seed germination, stem elongation, and flowering (Yamaguchi and Kamiya, 2000; Binenbaum et al, 2018). In “green revolution” wheat, orthologues of the Arabidopsis Gibberellin Insensitive (GAI) gene, which plays roles in GA signaling, are mutated. Other numerous dwarf maize mutants have been reported (Bensen et al, 1995; Winkler and Helentjaris, 1995; Lawit et al, 2010; Jiang et al, 2012; Chen et al, 2014), but none of them can play the same essential roles as “green revolution” rice or wheat. The ectopic expression of Arabidopsis GA20ox in transgenic tobacco increased bioactive GA levels and stimulated the growth plants (Sophia et al, 2004). There are no reports of the gene editing of GA biosynthesis-related genes for the generation of dwarf or semidwarf maize plants. Gene-edited “transgene-free” dwarf maize plants were generated, which might be useful for maize breeding in the future
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