Functional divergence of a trypsin protease underpins phosphate signaling in a diatom.

-dependent protein kinase expression, consistent with a role in signal integration rather than bulk proteolysis. Comparative analyses indicated that PtTryp8 has diverged functionally from other trypsin paralogues, supporting isozyme specialization within diatom protease families. Together, these findings reveal a previously unrecognized role for proteolytic signaling in phosphate sensing and acclimation and suggest that regulatory diversification of proteases represents a general strategy for nutrient adaptation in photosynthetic eukaryotes.