Molecular characterization, expression and antibacterial function of a macin, HdMac, from Haliotis discus hannai.

Macins are a family of antimicrobial peptides, which play multiple roles in the elimination of invading pathogens. In the present study, a macin was cloned and characterized from Pacific abalone Haliotis discus hannai (Designated as HdMac). Analysis of the conserved domain suggested that HdMac was a new member of the macin family. In non-stimulated abalones, HdMac transcripts were constitutively expressed in all five tested tissues, especially in hemocytes. After Vibrio harveyi stimulation, the expression of HdMac mRNA in hemocytes was significantly up-regulated at 12 hr (P < 0.01). RNAi-mediated knockdown of HdMac transcripts affected the survival rates of abalone against V. harveyi. Moreover, recombinant protein of HdMac (rHdMac) exhibited high antibacterial activities against invading bacteria, especially for Vibrio anguillarum. In addition, rHdMac possessed binding activities towards glucan, lipopolysaccharides (LPS), and peptidoglycan (PGN), but not chitin in vitro. Membrane integrity analysis revealed that rHdMac could increase the membrane permeability of bacteria. Meanwhile, both the phagocytosis and chemotaxis ability of hemocytes could be significantly enhanced by rHdMac. Overall, the results showed that HdMac could function as a versatile molecule involved in immune responses of H. discus hannai.

Characteristic and antibacterial effect of a histone H2A and its preliminary roles in extracellular traps in manila clam Ruditapes philippinarum.

In the present study, a histone H2A (designed as RpH2A) was identified and characterized from clam Ruditapes philippinarum, and its open reading frame (ORF) was of 387 bp encoding a polypeptide of 128 amino acids. The deduced amino acid sequence of RpH2A shared high identities ranging from 57.1% to 96.1% with that of other identified H2A. The mRNA expression of RpH2A was up-regulated significantly after Vibrio anguillarum challenge. The recombinant RpH2A protein (rRpH2A) displayed significantly binding affinity to lipopolysaccharide (LPS) and peptidoglycan (PGN) in vitro, and also exhibited antimicrobial properties against Escherichia coli. In addition, the antimicrobial RpH2A was shown to co-localize with extracellular traps (ETs) released from hemocytes induced by E. coli, suggesting that RpH2A might contribute to eliminate invading bacteria in clam ETs. Altogether, our data revealed that RpH2A could function as antimicrobial peptides, which might play a crucial role in the immune responses of hemocytes ETs in clams.

Phytochemical, cytotoxic and chemotaxonomic study on Ajuga forrestii Diels (Labiatae).

A phytochemical investigation of Ajuga forrestii Diels led to the isolation of 14 compounds, including eight neo-clerodane diterpenes (1-8), two phytoecdysteroids (9, 11), one stigmastane sterol (10) and three iridoid glycosides (12-14). The structures of these compounds were identified by spectroscopic methods and a comparison of their data with those reported in the literature. This is the first report of compounds 1-14 from A. forrestii. The cytotoxic activities of the aqueous extract of A. forrestii and several compounds have been studied and the chemotaxonomic significance of isolated compounds has also been summarised.