MiPEPs and cPEPs as tools to monitor plant gene expression and develop alternative strategies in agriculture.

In order to develop a sustainable agriculture respecting the environment and to reduce chemical inputs, a new strategy has emerged in recent years, based on the use of products targeting plants' natural defense and growth mechanisms. In this context, a few years ago we demonstrated the existence in plants of regulatory peptides called miPEPs for "microRNA-encoded peptides". MicroRNAs (miRNAs) are small RNAs that down-regulate the expression of numerous genes in eukaryotes. MiPEPs increase the amount of their cognate miRNA, resulting in an even greater decrease in the expression of genes targeted by these miRNAs. Thus, the application of an artificial miPEP to a plant causes a phenotype associated with a change in the genes targeted by the corresponding miRNA. More recently we also identified new regulatory peptides, namely cPEPs for "complementary peptides", capable of enhancing the activity of a given protein, independently of any increase in transcriptional activity. Moreover, as for the miPEPs, the external application of these new peptides makes it possible to regulate the phenotypes associated with the targeted proteins. This review highlights the most recent advances in the potential use of miPEPs and cPEPs in agronomy to improve plant development and stress tolerance.