| Pinctada fucata is one of the most important sea pearl oyster, however, has notcompletely elucidated the formation of pearls at molecular level. The process of Pearls’formation are called biomineralization,which composed of a series of process that guide thecrystallizetion of CaCO3by a serise of matrix proteins, but on their mechanism of action atthe molecular level, the relationship among multiple matrix proteins, the relationships withtheri counterpart in other closely related species, and the regulation for expression level etal, the current research are unable to give full explanation. The experimental work done twomajor areas:(1) investigate the expression pattern of an important matrix protein in P. fucataunder various environmental factors;(2) find a new shell matrix proteins, and furtherforecasting and analysising its structure and function. We intend to carry out such work, tomake a preliminary research for studying the formation mechanism of shells and pearls.Central composite design method was used to study the combined effect of temperatureand salinity on the Nacrein’s gene expression level in red color breeding lines P. fucata. Theresults showed that:(1) the liner effects of temperature and salinity effects on Nacrien’s geneexpression were significant (P <0.05), the quadratic effect were very significant effect (P<0.01), but the interaction effects between the two was not significant (P>0.05). Throughoptimization for the model, the optimal combination of temperature and salinity obtained was26.1℃,30.6ppt, at this point, the relative expression is0.509, which corresponding thelagest value, and the satisfaction of model is100%.By designing a Ca2+concentration gradient and Mg2+concentration gradient, Westudyed the combined effects of Ca2+and Mg2+on Nacrein gene expression levels in redshell color breeding lines P fucata. The results showed that the gene expression significantincreased with Ca2+concentration, and the liner effects and quadratic effects of Ca2+concentration was highly significant (P <0.01). Based on the above processing, eachequivalent amount of Mg2+was added, found, Mg2+gene expression levels showedsignificant differences between before and after treatment, and Mg2+concentration in avery significant effect（P＜0.01）. But the interaction effect of Ca2+and Mg2+was notsignificant (P>0.05). This suggests, in a certain concentration range, Ca2+and Mg2+Nacrein gene expression has significantly promoted Nacrein’s gene expression, and exsitsan optimal Ca2+concentration which correspond to the highest gene expression quantities.We used5’RACE technique for cloning a complete cDNA of a matrix of the gene. By predicting its protein squence, we found that the protein squence contains a singal peptidewhich composed of19amino acid in its N-terminal, typically comprising Gly-rich region anda C terminal conserved RKKKY sequence. Homology analysis shows that this is a newlydiscovered family members, which belongs to the same subfamily with Shematrin-2, sonamed Shematrin-2β. Further than the discovery, Shematrin-2β and MSI7has a high degreematching in local area, both probably have special evulutionary relationship. Amino acidcomposition analysis showed that, Shematrin-2β may confer special pearl shell andmechanical properties, contributes to build scaffold protein involved biomineralization, andmediates other proteins involve this process by interacting with them. RT-PCR showed,Shematrin-2β gene was expressed in the mantle edge and mantle pallial, suggesting that thematrix proteins may have a role in the construction of nacre and prismatic layer. The researchresults filled the vacancy of Shematrin family, for further study of the relationship betweenshematrins and biomineralization has a certain significance. |
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