Goldsinny wrasse (Ctenolabrusrupestris) is an extreme vtgAa‐type pelagophil teleost

Abstract

During oocyte maturation in the goldsinny wrasse (Ctenolabrus rupestris) extensive proteolysis of yolk proteins generates a large pool of free amino acids that drive hydration of the pelagic egg. By cloning hepatic vitellogenins (vtg) and using mass spectrometry, N-terminal microsequencing, and Western-immunoblotting to identify the yolk proteins (Yp), we show that multiple forms of vitellogenin mRNAs (vtgAa, vtgAb, and vtgC) are expressed in the liver, but only a single major class of the Yps derived from vtgAa predominates in the oocytes. Some Yps derived from vtgAb and vtgC appear also to be incorporated in the oocytes and eggs, but only at background levels. During oocyte hydration the vtgAa-derived lipovitellin heavy chain (LvH-Aa) and its cleavage variants are completely degraded leaving only a processed lipovitellin light chain (LvL-Aa) fragment as the major yolk protein for embryonic development. The maturational cleavage site of the LvL-Aa is identified as two amino acids downstream from the conserved Tyr(1168) of VtgAa in Atlantic halibut. In addition, although a beta'-component (approximately 18 kDa) is present in the oocytes, it is not fully degraded during the hydration process.