A small peptide miPEP172b encoded by primary transcript of miR172b regulates salt tolerance in rice

Recent studies have demonstrated that the primary transcript of miRNAs (pri-miRNAs) are able to encode small peptides influencing plant growth and development, as well as responses to various environmental cues. However, their role in plant responses to salt stress is not fully comprehended. Here, we characterized a short peptide encoded by miR172b (miPEP172b) in rice (Oryza sativa L.). By applying synthetic miPEP172b, we observed a significant increase in miR172b abundance and a decrease in the expression of its target gene IDS1. Consequently, plants treated with miPEP172b exhibited enhanced tolerance to salinity stress. Furthermore, we found that miPEP172b was efficiently absorbed by roots and transported to the aerial parts of the plant, thus conferring salt tolerance in the aboveground organs. Overexpression of miPEP172b resulted in reduced levels of reactive oxygen species (ROS), leading to improved performance of rice seedlings under salinity conditions. This was consistent with the observations in miR172-overexpressing plants. Conversely, miPEP172b mutants showed increased sensitivity to salt stress. Further analysis revealed that miPEP172b-miR172-IDS1 improved rice salt tolerance by integrating the ROS scavenging pathway and plant hormone signaling. Our findings highlight the significant role of miPEP172b in regulating miR172 activity and salt tolerance, providing a useful agent for improving crop salt tolerance.