Lipid transfer proteins (LTPs) in plants. An approach to the
knowledge of pollen and allergen diversity
María Suárez-Cervera1; Ana Vega-Maray2; F. Javier Rodríguez-Rajo3; Juan A.
Asturias4, Annick Le Thomas5, Juan A. Seoane-Camba1
1
Department of Botany, Faculty of Pharmacy, University of Barcelona, Av. Diagonal
s/n, 08028 Barcelona, Spain.
2
Department of Biodiversity and Environmental Management (Botany), Faculty of
Biology, University of León, Campus de Vegazana s/n, 24071 León, Spain
3
Dept. Plant Biology and Soil Sciences, Sciences Faculty of Ourense, University of
Vigo, Ourense, Spain;
4
Bial-Arístegui, R&D Department, 48008 Bilbao, Spain
5
Museum national d’Histoire Naturelle. Paris, France
In spite of the great diversity of pollen grains, the same diversity does not apply to
allergenic proteins. Of the 7,868 protein families found in all plant proteins, only 29
contain pollen allergens. Non-specific plant lipid transfer proteins (nsLTPs) are small
proteins (9 kD) which are widely distributed across the plant kingdom and form part of
the plant defence system. NsLTPs are identified as major allergens in fruits, and
frequently associated with pollen allergy. The aim of the present study is to localize the
peach nsLTP, Pru p 3, in pollen grains of taxonomically distant plants, such as
Parietaria judaica, Platanus acerifolia and Aristea latifolia, in order to compare pollen
biodiversity to nsLTP protein diversity. A combination of transmission electron
microscopy, immunocytochemical techniques, and rabbit specific antiserum against
peach nsLTPs were used. Abundant labelling against Pru p 3 was observed in the
cytoplasm, walls and pollenkitt of Aristea latifolia pollen grains. The presence of
nsLTPs associated with the pollenkitt proves that the pollenkitt takes part in the defence
mechanism of pollen grains. The labelling was less intense in the cytoplasm and walls
of Platanus acerifolia. The gold particles were associated with the vacuoles, lipid
inclusions, endoplasmic reticulum and Golgi complex. No significant labelling was
found in the Parietaria judaica pollen grains incubated with Pru p 3. This was expected
because Par j 1-2 and Pru p 3 nsLTPs have strong sequence divergence. These results
indicate important variations in the nsLTPs of different pollen species. Consequently,
no taxonomical relationship between pollen grains and nsLTPs could be established.
Grant CGL2006-15103-C04-01 from the Department of Education and Science of
Spain.