Emerging roles of microproteins in plant developmental regulation, stress adaptation and crop improvement

Abstract

Microproteins (miPs) are small regulatory proteins, typically fewer than 150 amino acids, that modulate plant gene regulatory networks, primarily through protein-protein interactions (PPI). By interacting with larger multidomain proteins, particularly transcription factors (TFs), miPs act as dominant-negative regulators that fine-tune transcriptional and signalling pathways involved in plant growth, development, and stress responses. Advances in genome annotation, ribosome profiling, and proteogenomics have revealed that numerous small open reading frames (sORFs) encode functional miPs, establishing them as important regulatory molecules rather than translational by-products. Initially characterized in Arabidopsis thaliana through the discovery of LITTLE ZIPPER (ZPR) proteins. Emerging evidence suggests that miPs may be associated in fruit development and ripening, although direct functional studies in fruit crops remain limited. This review, primarily focuses on classical plant miPs that modulate protein activity through dominant-negative PPI, while also briefly discussed associated classes of small regulatory peptides, where they intersect functionally with miP-mediated regulation. Recent advances in computational prediction, high-resolution proteomics, and genome editing technologies are accelerating the identification and characterization of plant miPs, offering promising opportunities to harness their regulatory potential for improving crop productivity, stress tolerance, and fruit quality. This review also focuses on the role of miPs in abiotic stress tolerance, secondary metabolism, vegetative and reproductive development, hormonal signalling, transcriptional regulation. In addition, it briefly describes the current technological advancement in the identification and characterization of plant miPs from model plant and crop species.