The X-ray crystal structure and biochemical analysis of a native basic pathogenesis-related-1 protein from Mucuna sempervirens (Fabaceae) floral nectar.
Zha HG, Cui P, Yu Y, Song YQ, Cheng MH
Plant Signaling
The proteins plants pump into their flowers may be doing jobs we haven't imagined yet — and understanding them could reshape how breeders think about pollinator attraction, nectar chemistry, and disease resistance in flowering vines and legumes.
Plants make a family of small proteins famous for helping them fight off diseases. Researchers found one of these proteins not in a sick leaf, but in the sweet nectar of a tropical vine's flower — and when they looked closely at its shape, it formed a paired structure and couldn't do any of the disease-fighting things its relatives do. That suggests this protein has been 'repurposed' by the plant for some completely different function in the flower, possibly related to pollination or nectar chemistry.
Key Findings
The protein MsPR-1b forms a homodimer (two identical units paired together) — the first native PR-1 protein ever crystallized directly from its natural plant source, resolved at 2.0 Å resolution.
Despite belonging to a protein family associated with immune defense, MsPR-1b shows no detectable lipid-binding ability and no direct antimicrobial activity.
The protein is expressed almost exclusively in the nectary (nectar-producing tissue), is not glycosylated, and has a basic character (pI 9.4, 15,134 Da), distinguishing it from typical acidic defense-related PR-1 proteins.
chevron_right Technical Summary
Scientists solved the 3D structure of a plant immune protein found in flower nectar — and discovered it looks and behaves nothing like its pathogen-fighting cousins, suggesting it has an entirely different, still-unknown job in the plant.
Abstract Preview
Pathogenesis-Related 1 (PR-1) proteins are small secreted proteins that typically accumulate upon pathogen attack and serve as hallmarks of plant immune activation. Despite their widespread use as ...
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Mucuna is a genus of vines and shrubs of the legume family Fabaceae: tribe Phaseoleae. It has a pan-tropical distribution and contains 112 accepted species as of July 2025. The genus was created in 1763 by French botanist Michel Adanson.