Pozzolini Marina, Ferrando Sara, Gallus Lorenzo, Gambardella Chiara, Ghignone Stefano, Giovine Marco
Department of Earth, Environmental and Life Science (DISTAV), University of Genoa, Corso Europa 26, 16132, Genoa, Italy;
Institute of Marine Sciences (ISMAR) - CNR, Via De Marini 6, I-16149, Genoa, Italy; and.
Biol Bull. 2016 Jun;230(3):220-32. doi: 10.1086/BBLv230n3p220.
The sponge Chondrosia reniformis selectively engulfs siliceous particles that, when in crystalline form, become quickly dissolved in its ectosome. The molecular mechanism, identity, and physiological significance of the cells involved in this process are not completely understood. In the present study, we applied light and electronic microscopic techniques to show how the quartz particles in C. reniformis are enveloped through collagen fibers and host cells near the surface of these organisms. As various aquaporins from bacteria, animals, and plants bidirectionally conduct metalloids-including silicon ions--through the cell membrane, the presence and potential involvement of aquaporins in quartz dissolution in C. reniformis have been investigated. An aquaporin-like transcript (CrAQP) was isolated according to the transcriptome sequencing results in C. reniformis The full-length CrAQP cDNA is 907 nucleotides long, with a 795-base pair (bp), open reading frame encoding a protein of 265 amino acids, a 29-bp, 5'-non-coding region, and a 83-bp, 3'-untranslated region. The Bayesian phylogenetic inference suggests that CrAqp is closely related to the Aqp8L grade, which is also implicated in H2O2 transport. Quantification of CrAQP mRNA through qPCR indicated that the transcript level was higher in the ectosome than in the choanosome. Immunofluorescence of a mammalian AQP8 in C. reniformis showed positivity in some cells near the quartz particles, a finding that may support the initial hypothesis of the potential involvement of CrAQP in quartz erosion. However, the features of the primary structure of this protein offer a new viewpoint about the functional role of these molecules in this process: that CrAQP may be involved in the permeation of H2O2 released during silica erosion.
海绵肾形软骨藻会选择性地吞噬硅质颗粒，这些颗粒呈晶体形式时会迅速溶解在其外质体中。目前对于参与这一过程的细胞的分子机制、特性及生理意义尚未完全了解。在本研究中，我们应用光学和电子显微镜技术来展示肾形软骨藻中的石英颗粒是如何通过胶原纤维以及这些生物体表面附近的宿主细胞被包裹起来的。由于来自细菌、动物和植物的各种水通道蛋白可双向传导包括硅离子在内的类金属物质通过细胞膜，因此对水通道蛋白在肾形软骨藻石英溶解过程中的存在及潜在作用进行了研究。根据肾形软骨藻的转录组测序结果分离出了一个类似水通道蛋白的转录本（CrAQP）。CrAQP cDNA全长907个核苷酸，有一个795个碱基对（bp）的开放阅读框，编码一个265个氨基酸的蛋白质，一个29 bp的5'非编码区，以及一个83 bp的3'非翻译区。贝叶斯系统发育推断表明CrAqp与Aqp8L等级密切相关，后者也与过氧化氢运输有关。通过qPCR对CrAQP mRNA进行定量分析表明，转录本水平在外质体中高于在中胶层中。在肾形软骨藻中对哺乳动物AQP8进行免疫荧光检测显示，在石英颗粒附近的一些细胞中呈阳性，这一发现可能支持了CrAQP潜在参与石英侵蚀的初步假设。然而，这种蛋白质一级结构的特征为这些分子在这一过程中的功能作用提供了一个新观点：即CrAQP可能参与了二氧化硅侵蚀过程中释放的过氧化氢的渗透。
