Plant biol (Stuttg) 2007; 9(6): 800-806
DOI: 10.1055/s-2007-965119
Short Research Paper

Georg Thieme Verlag Stuttgart KG · New York

In Vitro Toxicity towards Kiwifruit Pollen of the Antimicrobial Peptides Magainins 1 and 2

A. M. Speranza1 , A. R. Taddei2 , E. Ovidi2
  • 1Dipartimento di Biologia ES, Università di Bologna, via Irnerio, 42, 40126 Bologna, Italy
  • 2CIME, Università della Tuscia, Largo dell'Università, snc, 01100 Viterbo, Italy
Further Information

Publication History

Received: December 19, 2006

Accepted: February 24, 2007

Publication Date:
12 June 2007 (eFirst)

Abstract

In vitro toxicity of the antimicrobial peptides (AMPs) magainin 1 and 2 to a higher plant organism, i.e., the bicellular male gametophyte of Actinidia deliciosa (kiwifruit), is investigated. Heavy damage to the plasma membrane, the primary cellular target of the peptides, was rapidly induced: in as few as 15 min, from 70 to nearly 100 % of pollen grains were rendered unviable by 20 µM magainin 1 or 2, respectively. Therefore, kiwifruit pollen sensitivity to natural magainins seemed to be higher if compared to the sensitivity of other pollen species towards magainin 2 amide or synthetic magainin analogues. Strong dose-dependent inhibitory effects on kiwifruit pollen performance were registered: as for magainin 1, the EC50 at 120 min varied from 14.0 (germination) to 15.8 µM (tube elongation). The inhibitory effect was much greater when administering magainin 1 to elongating tubes rather than to ungerminated pollen grains. The two peptides differentially affected kiwifruit pollen, in line with the previously documented greater activity of magainin 2 in other cell systems. Furthermore, 20 µM magainin 1-treated pollen grains took on a shrivelled shape within 30 min of incubation, an increasingly widespread effect with higher peptide concentration. At the ultrastructural level, both protoplast shrinkage and striking organelle alterations were evident, including chromatin condensation, swelling and loss of mitochondrial cristae, dilation of rough endoplasmic reticulum cisternae, and vacuolization of cytoplasm. To our knowledge, similar alterations in animal or plant cells treated with AMPs have not been described yet.