Developmental and quantitative expression profile of the six pollen allergens of mugwort (Artemisia vulgaris L.)

Artemisia vulgaris L. (Asteraceae family), a wind-pollinated perennial weed, is a significant source of allergenic pollen, responsible for respiratory allergies in late summer. Six allergenic proteins-Art v 1, Art v 2, Art v 3, Art v 4, Art v 5, and Art v 6-have been identified in A. vulgaris pollen. However, knowledge regarding significant scientific questions, such as where, when, and in what quantities these proteins are expressed, remains limited.

This study fills these gaps by determining the expression profiles of all six genes encoding allergenic proteins in mugwort pollen. The real-time PCR method was used to analyze the level of allergen expression at three stages of pollen development: microsporocytes before meiosis (stage I), tetrads after meiosis (stage II), and enclosed mature pollen (stage IIIa), as well as isolated mature pollen grains (stage IIIb). The results showed that the expression levels of the most immunogenic allergens, Art v 1 and Art v 3, are extremely high at stage IIIa but very low at stage IIIb, suggesting their production occurs in mature inflorescence tissues. The expression levels of these two major allergens are significantly higher than those of other minor allergens in Artemisia pollen. Art v 2 is expressed in both pollen grains and anther tissues, whereas Art v 5 and Art v 6 are transcribed only in mature pollen, with no noticeable expression in earlier stages of pollen development. Art v 4 expression begins at the tetrad stage and reaches its highest levels in mature pollen grains, where it surpasses the expression level of all other allergens.

Our study provides new insights into allergen expression in A. vulgaris pollen, highlighting significant quantitative and developmental differences. These findings may help explain why some proteins are more likely to cause pollen allergies than others.