Résumé
Mytilus is a bivalve species with important economic and ecosystem value over worldwide. Mytilus antimicrobial peptides‚ with strong molecular diversity‚ has become a research focus. Two novel antimicrobial peptides were identified from Mytilus‚ with structural features that similar to arthropod defensins. However‚ the functional features and the immune mechanism of these two mussel defensins are unknown. For this reason‚ the two novel defensins‚ Arthropod like defensn-1 and -2 (ALD-1 and ALD-2‚ respectively)‚ were studied for the sequence features‚ expression profiles‚ and the dynamic expression pattern after different microbe induction. In addition‚ solid phase chemical synthesis technology was used for the synthesis of these two novel ALDs‚ and the function of synthesized peptides of ALD was verified. The results indicated that‚ two ALDs of M. coruscus have classical structure features similar to those of other arthropod defensins. These two ALDs are mainly presented in the tissues of mantle and digestive gland of mussel. The results also suggest that ALD-1 was expressed at higher levels in the gonads of males than in females (P<0. 05). The expression of two ALDs is developmentally regulated‚and both ALD-1 and ALD-2 were undetectable in larvae‚ but can be detected with high expression level at adult mussel with age of six months. The dynamic changes in the expression level of two ALDs after microbial induction were examined‚ and the results showed a marked increase in expression level observed in vivo for both ALDs. Interestingly‚ two ALDs showed different sensitivities to different microbes‚ indicating very complex responses during the mussel immune response. This observation strongly suggests the existence of different recognition mechanism or signal transduction pathway in mussels for the expression of ALD-1 and ALD-2. Moreover‚ both of two chemical synthesized ALDs showed significant antimicrobial activities against five tested microbes with an inhibition ratio of 20%-80%. These results provided basis for understanding the molecule mechanism of Mytilus immunology‚ and the function of novel Mytilus defensins‚ and thusly provided basis for the development of molecular resource for mussel antimicrobial peptides.