Abstract

DELLA proteins are central repressors of gibberellin (GA) signaling in plants. In Arabidopsis and rice, gain- and loss-of-function mutations in DELLA genes confer semidwarf and slender phenotypes, respectively. However, studies in Arabidopsis and tomato have suggested that a subset of GA responses can be mediated through DELLA-independent pathways. To date, no loss-of-function DELLA mutant has been characterized in maize. Here, we report the identification of a novel dominant maize DELLA mutant, D8-3 , which exhibits a dwarf phenotype associated with reduced cell elongation. We show that an E602K amino acid substitution in the C-terminal GRAS domain markedly increases D8 protein stability. To investigate DELLA function in maize, we generate single and double loss-of-function mutants of the two maize DELLA homologs using genome editing. In contrast to observations in rice, disruption of DELLA function does not result in a slender growth phenotype in maize. Transcriptome analyses further reveal that expansin genes, which were strongly induced in the rice slender rice1 ( slr1 ) mutant, are not significantly upregulated in maize DELLA loss-of-function mutants. Together, our findings uncover both conserved and maize-specific mechanisms governing DELLA regulation and function, providing new insights into the diversification of GA signaling pathways in plants.