The emerging role of cysteine-rich peptides in pollen–pistil interactions.

This article focuses on the critical roles of cysteine-rich peptides (CRPs) in regulating sexual reproduction in flowering plants, particularly during pollination and double fertilization. It reviews four main classes of CRPs—rapid alkalinization factors (RALFs), thionins, defensins/defensin-like proteins, and lipid transfer proteins (LTPs)—and their involvement in key reproductive stages including pollen–stigma recognition, pollen tube growth and guidance, pollen tube rupture, and gamete fusion. The article highlights molecular mechanisms such as self-incompatibility and self-compatibility systems mediated by CRPs, species-specific pollen tube attractants, and signaling pathways that prevent polyspermy and ensure fertilization success. It also discusses unresolved questions about CRP functions and receptor interactions, emphasizing the potential applications of this knowledge in crop breeding and plant reproductive biology research.