Cysteine-rich peptides promote interspecific genetic isolation in Arabidopsis

Racing to fertilization Pollen tubes, which carry plant sperm, need to grow from where they land in the flower to where the ovule is. Zhong et al. now show how pollen from related plant species race to reach the ovule first. One set of fast-evolving peptide signals is tuned to speed up growth of conspecific pollen tubes. A related set of evolutionarily ancient peptides is tuned to attract all pollen tubes. Thus, fertilization is more likely to happen through conspecific pollen tubes, but a fail-safe system encourages even the laggards to get where they need to go. Science , this issue p. eaau9564