Peptides: Opening the door

Interspecific isolation is a common mechanism adopted by plants to prevent gene flow between diverged species, thus maintaining species genetic integrity. However, from a plant breeder’s perspective, hybridization is desirable, as it can provide a wider range of agriculturally important traits for crop improvement ( Tonosaki et al., 2016 ). Although significant progress has been made in recent years in our understanding of some key factors controlling pollen–pistil interactions within species, we still know virtually nothing about the genetic and molecular basis underlying interspecific incompatibility. Recently, a research team led by Li-Jia Qu has reported that pollen-expressed RAPID ALKALINIZATION FACTOR (pRALF) peptides unlock a stigmatic barrier established by interaction between Catharanthus roseus RLK1-like (CrRLK1L) protein kinases and stigma-expressed RALFs (sRALFs) required for pollen penetration ( Lan et al., 2023 ). This groundbreaking finding not only provides novel insights into pollen–pistil interaction but also has implications for achieving hybrids between distantly related plants for crop breeding.