Fishery College, Guangdong Ocean University, Zhanjiang 524025, China.
Fishery College, Guangdong Ocean University, Zhanjiang 524025, China; Pearl Breeding and Processing Engineering Technology Research Centre of Guangdong Province, Zhanjiang 524088, China; Guangdong Science and Innovation Center for Pearl Culture, Zhanjiang 524088, China; Guangdong Provincial Engineering Laboratory for Mariculture Organism Breeding, Zhanjiang 524088, China.
Comp Biochem Physiol B Biochem Mol Biol. 2021 Oct-Dec;256:110615. doi: 10.1016/j.cbpb.2021.110615. Epub 2021 May 8.
Nicotinic acetylcholine receptors (nAChRs) are a class of ligand-gated ion channels that participate in signal transduction and are reported to play an important role in the immunomodulation of vertebrates and invertebrates. Previous studies have shown that the nAChRs in mollusks have undergone large-scale expansion after tandem repeats and retrotransposition, with the most expansion observed in bivalves. This study characterized the sequence of a tandem repeat nAChR unique to several bivalve mollusks and investigated its functions in Pinctada fucata martensii. Firstly, phylogenetic analysis revealed that the tandem arrays of nAChRs existed before bivalve differentiation and m ost tandem-replicated nAChR genes have a conserved genomic structure and domain combination. In present study, five tandemly duplicated nAChR genes were cloned from P. f. martensii and designated as PmnAChR-1 to PmnAChR-5. qRT-PCR analysis revealed that five PmnAChRs were specifically expressed in adult gills. In addition, after PAMP stimulation, the expression of PmnAChRs in hemocytes of P. f. martensii were strongly induced but exhibited different responses to different stimuli. PmnAChR-1, PmnAChR-4, and PmnAChR-5 exhibited strong and wide responsiveness to lipopolysaccharide (LPS) stimulation but had no response to peptidoglycan (PGN) stimulation. PmnAChR-2 expression was notably upregulated at 6 h after PGN challenge but had no response to LPS stimulation. Polyinosinic-polycytidylic acid challenge upregulated nearly all PmnAChRs, except for PmnAChR-5. Furthermore, Pm-miR-873-3p, Pm-miR-4577, Pm-miR-103a-3p, and Pm-miR-6753-3p were identified as the regulatory miRNA of PmnAChR-1, PmnAChR-3, PmnAChR-4, and PmnAChR-5, respectively. These findings suggested that these tandem arrays of nAChRs are unique to bivalves, and the tandem duplication of nAChR genes may be involved in the immune regulation process after pathogen stimulation.
烟碱型乙酰胆碱受体 (nAChRs) 是一类配体门控离子通道，参与信号转导，据报道在脊椎动物和无脊椎动物的免疫调节中发挥重要作用。先前的研究表明，软体动物中的 nAChRs 经历了串联重复和反转录转座后的大规模扩张，其中双壳类动物的扩张最为明显。本研究对几种双壳贝类特有的串联重复 nAChR 序列进行了特征描述，并研究了其在马氏珍珠贝中的功能。首先，系统发育分析表明 nAChR 串联阵列存在于双壳类分化之前，并且大多数串联复制的 nAChR 基因具有保守的基因组结构和结构域组合。在本研究中，从马氏珍珠贝中克隆了五个串联重复的 nAChR 基因，并命名为 PmnAChR-1 到 PmnAChR-5。qRT-PCR 分析表明，五个 PmnAChRs 特异性表达于成年鳃中。此外，在 PAMP 刺激后，马氏珍珠贝血细胞中的 PmnAChRs 表达强烈诱导，但对不同刺激的反应不同。PmnAChR-1、PmnAChR-4 和 PmnAChR-5 对脂多糖 (LPS) 刺激表现出强烈而广泛的反应，但对肽聚糖 (PGN) 刺激没有反应。PmnAChR-2 的表达在 PGN 挑战后 6 小时显著上调，但对 LPS 刺激没有反应。多聚肌苷酸-多聚胞苷酸刺激几乎上调了所有的 PmnAChRs，除了 PmnAChR-5。此外，鉴定出 Pm-miR-873-3p、Pm-miR-4577、Pm-miR-103a-3p 和 Pm-miR-6753-3p 分别为 PmnAChR-1、PmnAChR-3、PmnAChR-4 和 PmnAChR-5 的调节 miRNA。这些发现表明，这些 nAChR 的串联阵列是双壳类特有的，nAChR 基因的串联重复可能参与了病原体刺激后的免疫调节过程。
