Spatio-temporal expression pattern and fasting response of follistatin gene in teleost Larimichthys crocea

Structural Characterization and Functional Analysis of the Follistatin Promoter of Larimichthys crocea

Follistatin is a secreted glycoprotein, which involved in numerous physiological activities as an antagonist of the transforming growth factor-β superfamily. However, little is known about the regulation mechanism of follistatin in fish. In this study we cloned and analyzed part of the 5' flanking region of the follistatin gene in Larimichthys crocea. Sequence analysis revealed several putative binding sites for transcription factors including activator protein 1 (AP1), myogenic differentiation factor (MyoD), stimulating protein 1 (SP1), and sex determining gene on the mammalian Y chromosome (SRY) in the cloned fragment. Transcriptional activities of two fragments (485 and 261 bp) truncated from follistatin upstream region were examined in vitro, using transient transfection in Ctenopharyngodon idella kidney (CIK) and Rattus norvegicus skeletal muscle myoblast (L6) cells. The result showed that the promoter activity correlated positively with the length of truncated fragments in both CIK and L6 cells. To study the regulation of follistatin expression in L. crocea, we cloned MyoD and SRY-box 8 (Sox8) genes and examined their action on the follistatin promoter by co-transfection in CIK and L6 cells. The results showed MyoD and Sox8 could suppress the activities of follistatin promoter at different levels in CIK and L6 cells.

Abundant members of Scavenger receptors family and their identification, characterization and expression against Vibrio alginolyticus infection in juvenile Larimichthys crocea

Scavenger receptors (SRs) are crucial pattern recognition receptors (PRRs) to defense pathogen infection in fish innate immunity. In this paper, some members in SRs family of Larimichthys crocea were identified, including eight genes in the class A, B, D and F families. (G + C) % of all SRs members held 51% ∼ 59%, and these genes were no obvious codon bias by analyzing the distribution of A-, T-, G- and C-ended codons. The order of Enc for all SRs members by sequencing was LycCD68 > LycSCARA5 > LycSCARB1 > LycCD163 > LycMARCO > LycSREC1 > LycSCARA3 > LycSREC2. Moreover, different lengths and numbers of exons and introns led to the diverse mRNAs and respective functional domains or motifs, for example, an optional cysteine-rich (SRCR) domain in LycMARCO and LycSCARA5, an epidermal growth factor (EGF) and EGF-like domain in LycSREC1 and LycSREC2. The sub-cellular localization demonstrated SRs members mainly located in plasma membrane or extracellular matrix. Further, all of the SRs members in L. crocea were almost low expressed in heart, gill and intestine, whereas high in spleen and liver. After stimulation by Vibrio alginolyticus, the class A and F families were induced significantly, but the class B and D families expressed less even none after pathogenic infection. All the findings would pave the way to understand not only the evolution of the SR-mediated immune response, but also the complexity of fish immunity.