Institute of Marine Biotechnology, School of Life Sciences, Tsinghua University, Beijing, 100084, China.
Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing, 100085, China.
Sci Rep. 2017 Aug 23;7(1):9219. doi: 10.1038/s41598-017-10011-y.
Mounting evidence suggests that TGFβ/BMP signaling pathway is most likely involved in shell biomineralization in molluscs, but the function of pathway receptors is poorly studied. Here, we cloned and identified two homologous BMP receptor genes, PfBMPR1B and PfBAMBI, from the pearl oyster Pinctada fucata. Real-time quantitative PCR and in situ hybridization revealed that these genes were expressed in mantle edge and pallial, specifically located at the outer epithelia. Knockdown of PfBMPR1B by RNA interference (RNAi) significantly decreased the expression levels of matrix protein (MP) genes and induced the abnormal ultrastructure of prismatic and nacreous layers. Conversely, knockdown of PfBAMBI significantly increased the expression levels of a portion of MP genes and induced the overgrowth of nacreous layer crystals. In the RNAi and shell notching experiments, MP gene expressions were competitively regulated by PfBMPR1B and PfBAMBI. In addition, the receptor inhibitor LDN193189 reduced the expression levels of MP genes in mantle primary cells and larvae, and induced abnormal D-shaped shell formation during larval development. Collectively, these results clearly show that PfBMPR1B and PfBAMBI are involved in regulating shell biomineralization in P. fucata. Our study therefore provides the direct evidence that BMP receptors participate in mollusc biomineralization.
越来越多的证据表明，TGFβ/BMP 信号通路很可能参与了软体动物的贝壳生物矿化，但该通路受体的功能仍研究甚少。本研究从珍珠贝（Pinctada fucata）中克隆和鉴定了两个同源的 BMP 受体基因 PfBMPR1B 和 PfBAMBI。实时定量 PCR 和原位杂交结果显示，这些基因在边缘膜和套膜中表达，特别是在外分泌上皮中。通过 RNA 干扰（RNAi）敲低 PfBMPR1B 显著降低了基质蛋白（MP）基因的表达水平，并导致棱柱层和珍珠层的超微结构异常。相反，PfBAMBI 的 RNAi 敲低显著增加了部分 MP 基因的表达水平，并导致珍珠层晶体的过度生长。在 RNAi 和贝壳缺口实验中，PfBMPR1B 和 PfBAMBI 对 MP 基因的表达具有竞争调控作用。此外，受体抑制剂 LDN193189 降低了外套膜原代细胞和幼虫中 MP 基因的表达水平，并在幼虫发育过程中诱导了异常的 D 形贝壳形成。综上所述，这些结果清楚地表明 PfBMPR1B 和 PfBAMBI 参与了珍珠贝贝壳生物矿化的调控。本研究因此提供了直接证据表明 BMP 受体参与了软体动物的生物矿化。
