Cytotoxic effect of benzo(a)pyrene on development and protein pattern of sunflower pollen grains

Abstract

Benzo(a)pyrene (BaP) is an important part of diesel exhaust particles (DEP). The overall objective of this research was to elucidate some microscopic effects of BaP on the formation, development, and structure of pollen grains and its proteins in sunflower (Helianthus annuus L). Sunflower plants were grown in experimental pots and treated with the different concentrations of BaP. Flowers and young buds were removed, fixed in FAA₇₀ (formalin:acetic acid:ethanol, 2 : 1 : 17) and subjected to developmental studies. Our results show that BaP-treatment causes abnormalities during pollen development. Shape of microspore tetrads changed from spherical to polygonal or irregular. Pollen grains in normal plants are spherical in both equatorial and polar views; in BaP-treated plants, they changed into irregular shapes in equatorial view and triangular shape in polar view. Delay in degeneration of the tapetum layer in anther, and formation of giant, irregular, and non-fertile pollen grains are other results of BaP treatment. Gel electrophoretic studies revealed that a band with a molecular mass of 30 kDa disappeared in the BaP-treated group and two new proteins with molecular masses of 15 and 20 kDa were formed. Some pollen proteins may act as allergens, considering the fact that pollen allergy frequency is increased in polluted areas, especially DEP-polluted ones; the possibility arises that BaP, as an important part of DEP, could be an effective agent entailing formation of detoxifying proteins which, on the other hand, can also act as allergens.

Keywords:

• air pollution
• benzo(a)pyrene
• Helianthus annuus
• pollen development
• pollen proteins

Acknowledgments

This research was done using financial support provided by research council of Bu-Ali Sina University and also Tarbiat Moallem University partly.