Synthesis of Phytosulfokine Analogs as Probes for Studying Plant Signaling and Molecular Trafficking

Plants are exposed to a wide range of biotic and abiotic stresses that hinder their growth and reduce crop productivity. In their adaptive response, plants use signaling molecules that are trafficked throughout the plant. This research focuses on the chemical synthesis and assessment of analogs of the plant signal phytosulfokine (PSK, a sulfated pentapeptide), its delivery to plants and its observation using a fiber-optic fluorescence microscope. PSK regulates growth, cell expansion, heat tolerance, and tissue longevity. Analogs of PSK were synthesized using solid-phase peptide synthesis. Pure PSK and TAMRA-labeled PSK were delivered into the wild-type Arabidopsis thaliana Col-0 and a transgenic line expressing PSKR-GFP (PSK receptor – green fluorescent protein). PSKR-GFP could be detected in imaging experiments, but no internalization was observed upon treatment with PSK. Successful implementation of a microscopic approach suited for live plants opens a path to understanding how plants signal and adapt under different stress conditions