A Structural Bridge Between Kingdoms: How Collagen-Derived Peptides Influence Plant Stress and Growth Pathways.

Collagen-derived protein hydrolysates (CDPH) are widely used as plant biostimulants primarily due to their content of bioactive oligopeptides. When applied to hydroponically grown Solanum lycopersicum plants, CDPH significantly promoted root development, particularly by increasing the number and length of lateral roots. To gain insight into the underlying molecular mechanisms, we hypothesized that plants may possess proteins capable of interacting with collagen-like peptides. To test this, we conducted a comprehensive homology search of the Arabidopsis thaliana proteome using a Hidden Markov model-based approach built from three human collagen-binding proteins (CBPs) and 14 known collagen-binding domains (CBDs). After filtering, 10 Arabidopsis proteins emerged as putative candidates with the potential to bind collagen. Notably, the highest homology was observed for a matrix metalloproteinase, At5-MMP, showing 44% identity with its human counterpart HsMMP1, and for AtSERPIN1, which displayed the strongest e-value match to HsSERPINH1 (22% identity). Both plant proteins are functionally associated with responses to abiotic and biotic stresses, a feature that mirrors the known physiological effects of CDPH-based biostimulants. These findings support the hypothesis that plants possess proteins capable of recognizing collagen-like structures, offering a plausible molecular basis for the activity of CDPH-based biostimulants and paving the way for future biochemical validation.