Identification and functional characterization of NEMO in Crassostrea gigas reveals its crucial role in the NF-κB activation.

NEMO (NF-κB essential modulator) is one of the important regulatory subunits of the IκB kinase (IκK) complex that controls the activation of the NF-κB signaling pathway. Here, we have identified the homolog of NEMO from the pacific oyster Crassostrea gigas. CgNEMO harbors the conserved the IκK binding region, NEMO ubiquitin binding domain and Zinc finger domain. In terms of tissue distribution, CgNEMO is expressed in various tissues with an observed highest expression in the hemocytes. Furthermore, infection by two related Vibrio strains significantly increased CgNEMO expression in the hemocytes. Cell culture based luciferase reporter assays showed that CgNEMO activates the NF-κB reporter in a dose-pendent manner. Moreover, CgNEMO was also found to counter the IkB-dependent inhibitory effect on NF-κB activation, providing a plausible mechanism of NF-κB activation by CgNEMO. Meanwhile, site-directed mutagenesis demonstrated that the putative ubiquitination site K535 is required for the activation of NF-κB, implying that ubiquitination of NEMO may be involved in regulating its activity. Finally, RNAi mediated knockdown of CgNEMO in vivo significantly compromised the bacterial induction of key cytokines TNF-α and IL-17, strongly suggesting a role for CgNEMO in acute immune defense in oyster. In conclusion, this study provides new insights into our understanding about the evolution of NEMO mediated NF-κB activation and the induction of cytokine. Our findings may provide valuable information about diseases control and management in oyster aquaculture.

Draft genome analysis of Dietzia sp. 111N12-1, isolated from the South China Sea with bioremediation activity

Abstract Dietzia sp. 111N12-1, isolated from the seawater of South China Sea, shows strong petroleum hydrocarbons degradation activity. Here, we report the draft sequence of approximately 3.7-Mbp genome of this strain. To the best of our knowledge, this is the first genome sequence of Dietzia strain isolated from the sea. The genome sequence may provide fundamental molecular information on elucidating the metabolic pathway of hydrocarbons degradation in this strain.

Draft genome analysis of Dietzia sp. 111N12-1, isolated from the South China Sea with bioremediation activity.

Dietzia sp. 111N12-1, isolated from the seawater of South China Sea, shows strong petroleum hydrocarbons degradation activity. Here, we report the draft sequence of approximately 3.7-Mbp genome of this strain. To the best of our knowledge, this is the first genome sequence of Dietzia strain isolated from the sea. The genome sequence may provide fundamental molecular information on elucidating the metabolic pathway of hydrocarbons degradation in this strain.

Identification and functional characterization of MRE-binding transcription factor (MTF) in Crassostrea gigas and its conserved role in metal-induced response.

The full-length cDNA that encodes the MRE-binding transcription factor (MTF) was cloned from the Pacific oyster (Crassostrea gigas) using reverse transcription polymerase chain reaction and the rapid amplification of cDNA ends. The cgMTF cDNA sequence is 2892 bp long, with a 2508 bp open reading frame that encodes an 835-amino acid polypeptide. Multiple alignment revealed that cgMTF has four putative zinc finger-like regions in cgMTF with three C2C2-type zinc fingers and one C2H2-type zinc finger. After 12 h of exposure to Cd(2+), the cgMTF mRNA level was increased in a dose-dependent manner, which then subsided with time. cgMTF stimulates the cgMT promoter reporter in the HEK293 cell line in a dose-dependent manner. When either of the metal-responsive elements (MRE1 or MRE2) of the cgMT promoter was mutated, the cgMT promoter reporter activity was significantly reduced. After the two MREs were mutated simultaneously, the promoter activity was completely abolished. In conclusion, we identified an MTF in C. gigas and revealed the presence of an evolutionarily conserved molecular mechanism for coping with environmental metal stress.