Differential Immune-Reactivity and Subcellular Distribution Reveal the Multifunctional Character of Profilin in Pollen As Major Effect of Sequences Polymorphism.

Profilin, one of the major allergen (Ole e 2) of olive (Olea europaea L.) pollen, are broadly distributed actin-monomer-binding proteins (ABP). They display a major regulatory role in actin cytoskeleton dynamics, driving cell morphogenesis, sexual reproduction, and translating signals into cellular responses to different environmental stresses.

Plants exhibit multiple profilin isoforms with distinctive biochemical properties, and differentially regulated. However, it is still an open question whether these profilin isoforms, generated by multiple gene sequence polymorphism, are functionally different, as well as the role of that polymorphism in pollen allergy. Particularly, in differential epitopes generation, profilin isoforms sensitization and cross-reactivity among cultivars, and even among species.

In the present study, we have used mature pollen from olive, birch, hazel, timothy-grass, and maize, in addition to olive germinating pollen and seeds, with the aim to analyze the immune-reactivity and subcellular localization of profilin by using polyclonal and specific isoforms antibodies against olive and maize profilins.

The results showed immune-reactivity differences between the five species analyzed, between olive cultivars, as well as between reproductive and vegetative profilins. Furthermore, the existence of different profilin isoforms was revealed along pollen germination stages.

A differential subcellular distribution of profilin isoforms was found in olive pollen. They were localized in the nucleus, pollen aperture regions, pollen and tube walls and pollen tip, in addition to a general cytoplasmic distribution, in comparison to controls.

Data suggest that profilin family might contain numerous functionally distinctive isoforms, spatial-temporal differentially expressed and regulated during vegetative development, pollen maturation and pollen tube growth. Furthermore, differential immune-reactivity revealed in the study might point out the involvement of common shared and specific epitopes, generated by sequence polymorphism, in differential olive pollen cultivar sensitization of allergenic patients, and cross-reaction to pollen from different species.