Bio-sintering processes in hexactinellid sponges: fusion of bio-silica in giant basal spicules from Monorhaphis chuni.
The two sponge classes, Hexactinellida and Demospongiae, comprise a skeleton that is composed of siliceous skeletal elements (spicules). Spicule growth proceeds by appositional layering of lamellae that consist of silica nanoparticles, which are synthesized via the sponge-specific enzyme silicatein. While in demosponges during maturation the lamellae consolidate to a solid rod, the lamellar organization of hexactinellid spicules largely persists. However, the innermost lamellae, near the spicule core, can also fuse to a solid axial cylinder. Similar to the fusion of siliceous nanoparticles and lamella, in several hexactinellid species individual spicules unify during sintering-like processes. Here, we study the different stages of a process that we termed bio-sintering, within the giant basal spicule (GBS) of Monorhaphis chuni. During this study, a major GBS protein component (27 kDa) was isolated and analyzed by MALDI-TOF-MS. The sequences were used to isolate and clone the encoding cDNA via degenerate primer PCR. Bioinformatic analyses revealed a significant sequence homology to silicatein. In addition, the native GBS protein was able to mediate bio-silica synthesis in vitro. We conclude that the syntheses of bio-silica in M. chuni, and the subsequent fusion of nanoparticles to lamellae, and finally to spicules, are enzymatically-driven by a silicatein-like protein. In addition, evidence is now presented that in hexactinellids those fusions involve sintering-like processes.
Müller
Werner E G
WE
Institute for Physiological Chemistry and Pathobiochemistry, Medical School, Johannes Gutenberg-University, Mainz, Germany. wmueller@uni-mainz.de
Wang
Xiaohong
X
Burghard
Zaklina
Z
Bill
Joachim
J
Krasko
Anatoli
A
Boreiko
Alexandra
A
Schlossmacher
Ute
U
Schröder
Heinz C
HC
Wiens
Matthias
M
D000825:Animal Structures / Q000033:anatomy & histology* / Q000737:chemistry* / Q000378:metabolism / Q000648:ultrastructure; D000818:Animals; D015152:Blotting, Northern; D008855:Microscopy, Electron, Scanning; D008969:Molecular Sequence Data; D011161:Porifera / Q000033:anatomy & histology* / Q000737:chemistry* / Q000378:metabolism / Q000648:ultrastructure; D012822:Silicon Dioxide / Q000737:chemistry / Q000378:metabolism*; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization
D012822:Silicon Dioxide