Floral innovation through modifications in stem cell peptide signaling.

Abstract

Understanding how evolution shapes genetic networks to create new developmental forms is a central question in biology. Asteraceae (sunflower family) comprise 10% of flowering plants and have capitula, a novel flowering shoot (inflorescence) that mimics a single flower (1, 2). During capitulum development, shoot stem cells undergo prolonged proliferation relative to other species (3, 4). Here we show that capitulum evolution paralleled decreases in CLAVATA3 peptide (CLV3p) signaling, a conserved repressor of stem cell proliferation. Asteraceae CLV3p displays reduced receptor binding and downstream transcriptional outputs. Reversion of CLV3 to a more active form impairs Asteraceae stem cell regulation and capitulum development. Lastly, we trace CLV3 evolution across the Asterales allowing inferences on capitulum evolution. Our findings reveal novel evolutionary mechanisms in plant reproduction and suggest approaches for engineering crops.