Increased allergen production in turnip (Brassica rapa) by treatments activating defense mechanisms.
BACKGROUND
Practical applications to enhance the productivity of agriculture by using plants with improved resistance to pathogens are expected to increase in the near future. Defense proteins play an important role in pathogen resistance, and some defense-related proteins are significant cross-reacting allergens. For example, cross-allergies are common among patients allergic to natural rubber latex (NRL), which contains many defense-related proteins.


OBJECTIVE
Using a model plant (ie, turnip), we studied whether allergen contents increase after treatments activating defense mechanisms of the plants.


METHODS
Whole or wounded turnips treated with salicylic acid, ethephon, or water were incubated for 2, 4, or 8 days. Allergen content was investigated by IgE immunoblotting with sera from patients allergic to NRL. An induced protein that bound IgE most intensively was purified and further characterized by mass analysis, amino acid sequencing, IgE-ELISA, and skin prick tests.


RESULTS
In immunoblotting, clear IgE-binding bands were discernible only in samples from chemically treated plants. IgE was bound most intensively to a protein with an apparent molecular weight of 25 kd in SDS-PAGE and with a determined molecular weight of 18.7 kd. Sequenced peptides of the 18.7-kd protein showed over 70% homology to prohevein, a major allergen of NRL, and to many other prohevein-like defense proteins. In ELISA, sera from 30 of 34 (88%) adults and 21 of 26 (81%) children previously shown to have IgE against prohevein bound to the purified protein. In skin prick testing with the protein, 4 of 6 patients allergic to NRL had positive reactions.


CONCLUSIONS
These results demonstrate that activating defense mechanisms of plants may considerably increase their allergen content.
National Public Health Institute, Helsinki; Institute of Occupational Health, Helsinki, Finland.
A R
AR
Hänninen
J H
JH
Mikkola
N
N
Kalkkinen
K
K
Turjanmaa
L
L
Ylitalo
T
T
Reunala
T
T
Palosuo
D000328:Adult; D000485:Allergens / Q000096:biosynthesis*; D001937:Brassica / Q000276:immunology* / Q000378:metabolism*; D002352:Carrier Proteins / Q000378:metabolism; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D006801:Humans; D007073:Immunoglobulin E / Q000378:metabolism; D020315:Latex Hypersensitivity / Q000097:blood / Q000188:drug therapy / Q000517:prevention & control; D008297:Male; D008875:Middle Aged; D010940:Plant Proteins / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism
D000485:Allergens; D002352:Carrier Proteins; D010940:Plant Proteins; D007073:Immunoglobulin E