Genome-wide identification and functional characterization of rapid alkalinization factor 6 as a key peptide...

Rapid alkalinization factors (RALFs) are cysteine-rich signaling peptides in plants that play critical roles in development, immune regulation, and responses to abiotic stress. Despite their importance, the functional characterization of RALF family members in Tartary buckwheat (Fagopyrum tataricum), a nutrient-rich crop known for its remarkable resilience to multiple stresses, remains largely unexplored. In this study, we conducted a comprehensive genome-wide analysis to identify and characterize the FtRALF gene family in Tartary buckwheat, examining their phylogenetic relationships, gene structures, and duplication events. RT-qPCR analysis revealed that FtRALF6 was strongly induced under heavy metal stress (200 μM CdCl₂ and 100 μM Sb), salt stress (150 mM NaCl), and temperature extremes (4°C chilling and 40°C heat). Functional assays demonstrated that exogenous application of synthetic FtRALF6 peptide alleviated stress-induced root growth inhibition, enhanced photosynthetic pigment content, and significantly reduced malondialdehyde levels and superoxide anion accumulation in roots. These findings uncover, for the first time, the physiological mechanism of FtRALF6 as a newly-found vital regulatory component in abiotic stress responses in Tartary buckwheat. This study not only introduces a promising peptide-based strategy for improving crop stress tolerance but also offers novel insights into the broader signaling networks underlying plant stress adaptation.