Maize YABBY drooping leaf genes regulate floret development and floral meristem determinacy

Abstract

Floret units in cereals produce grain, directly impacting yield. Here we report mutations in the maize CRABS CLAW (CRC) co-orthologs drooping leaf1 (drl1) and drl2 alter the development of ear and tassel florets. Pistillate florets of drl1 ears appear sterile and display ectopic unfused carpels that fail to enclose an expanded nucellus. Staminate florets of drl1 tassels have extra stamens and retain fertile anthers. Natural variation and transposon alleles of drl2 enhance drl1 floret phenotypes by reducing floral meristem (FM) determinacy. The drl paralogs are co-expressed in lateral floral organ primordia, but not within the FM. Together, the expression patterns and indeterminate mutant FMs suggest that the drl genes regulate FM activity and impose meristem determinacy by a non-cell autonomous signal. Genetic interaction analyses of drl mutants with maize floral mutants indicate that the drl genes are required throughout floret development, illustrating their importance for proper floret patterning in maize.