Drought conditions impact plants at the morphological, physiological, and molecular levels. Plant tolerance to drought conditions is frequently associated with maintaining proteome stability, highlighting the significance of proteomic analysis in understanding the mechanisms underlying plant resilience. Here, we performed proteomic and peptidomic analysis of spring wheat (Triticum aestivum L.) under drought stress conditions. Using isobaric tags for relative and absolute quantitation (iTRAQ), we identified 497 and 157 differentially abundant protein (DAP) groups in leaves and roots, respectively. The upregulated DAP groups in leaves were primarily involved in stress responses, such as oxidative stress and heat response, whereas those in roots were associated with responses to water deprivation and sulfur compound metabolic processes. The analysis of the extracellular root peptidome revealed 2294 native peptides, including members of small secreted peptide (SSP) families. In the peptidomes of stress-induced plants, we identified 16 SSPs as well as peptides derived from proteins involved in cell wall catabolism, intercellular signaling, and stress response. These peptides represent potential candidates as regulators of drought responses. Our results help us to understand adaptation mechanisms and develop new agricultural technologies to increase productivity.

Plant growth and development are inextricably connected with rhizosphere organisms. Plants have to balance between strong defenses against pathogens while modulating their immune responses to recruit beneficial organisms such as bacteria and fungi. In recent years, there has been increasing evidence that regulatory peptides are essential in establishing these symbiotic relationships, orchestrating processes that include nutrient acquisition, root architecture modification, and immune modulation. In this review, we provide a comprehensive summary of the peptide families that facilitate beneficial relationships between plants and rhizosphere organisms.

Cysteine-rich peptides belonging to the EPF/EPFL (epidermal patterning factor/epidermal patterning factor-like) family are common in many plants, from mosses to angiosperms. EPF/EPFL play an important role in morphogenesis: they regulate stomatal patterning, the functioning of the shoot apical and lateral meristems, inflorescence architecture, vascular development, growth of leaf margin, as well as the development of flowers and fruits. Recent studies have indicated that EPFL may be involved in plant adaptation to biotic and abiotic stress. This review examines the structure, phylogenetic distribution, mechanisms of signal transduction, and functions of the EPF/EPFL peptide family.

Small secreted peptides (SSPs) are a promising class of signaling molecules that regulate plant growth, development, and stress responses. Under abiotic stress conditions, SSPs can modulate the physiological and molecular responses, thereby influencing plant adaptation. Based on publicly available transcriptomic data on Arabidopsis thaliana, SSP gene expression was analyzed in plants exposed to dehydration or a higher salinity in combination with inoculation by plant growth-promoting bacteria (PGPBs). Candidate genes involved in plant adaptation to stress conditions upon interaction with PGPBs were thus identified. In salt stress, inoculation with Enterobacter sp. SA187 mitigated stress‑induced suppression of growth‑related genes. In dehydration stress, Aeromonas sp. H1 altered expression of genes regulating stomatal development and the root system, but did not affect SSP expression in mock conditions. A combined effect of stress and PGPBs was found to generate a specific transcriptional response. The response is not a simple overlay of two independent reactions, but depends on both the stress type and the bacterial strain.