Pretreatment with 43 nM (10 ng/mL) to 86 nM melatonin for 5 days significantly attenuated cold-induced apoptosis in carrot suspension cells (Daucus carota L.) as evidenced by the TUNEL procedure, DNA fragmentation and the morphological changes revealed by electronic microscopy observations. The antiapoptotic effect of melatonin was initially thought to be a result of its antioxidant actions. In our study, however, reactive oxygen species (ROS) generation remained unaffected by melatonin treatment, suggesting that melatonin plays its protective role not related to its direct ROS scavenger. At the same time, notable increases in putrescine and spermidine levels were observed in melatonin-treated cells, which may be responsible for the alleviation of the cold-induced apoptosis. The possible involvement of polyamines in the antiapoptotic effect of melatonin was further confirmed by the inhibitory effect of exogenous polyamines on apoptosis as displayed by the DNA laddering assay.
Background:The microstructure of nacre is controlled by the proteins in them. Results: When PfN23 was knocked down, the shell formation in adults and larvae was suppressed.
Conclusion:The basic protein PfN23 is important for the control of crystal growth in nacre. Significance: This might provide a valuable complementary to the classic view that acidic proteins control nacre formation.
To study the function of pearl oyster matrix proteins in nacreous layer biomineralization in vivo, we examined the deposition on pearl nuclei and the expression of matrix protein genes in the pearl sac during the early stage of pearl formation. We found that the process of pearl formation involves two consecutive stages: (i) irregular calcium carbonate (CaCO 3 ) deposition on the bare nucleus and (ii) CaCO 3 deposition that becomes more and more regular until the mature nacreous layer has formed on the nucleus. The low-expression level of matrix proteins in the pearl sac during periods of irregular CaCO 3 deposition suggests that deposition may not be controlled by the organic matrix during this stage of the process. However, significant expression of matrix proteins in the pearl sac was detected by day 30 -35 after implantation. On day 30, a thin layer of CaCO 3 , which we believe was amorphous CaCO 3 , covered large aragonites. By day 35, the nacreous layer had formed. The whole process is similar to that observed in shells, and the temporal expression of matrix protein genes indicated that their bioactivities were crucial for pearl development. Matrix proteins controlled the crystal phase, shape, size, nucleation and aggregation of CaCO 3 crystals.
Background: Thermodynamically unstable magnesium calcite is deposited in the shell of pearl oysters at ambient pressure. Results: The novel acidic matrix protein PfN44 interacts with magnesium to inhibit the deposition of aragonite. Conclusion: PfN44 participates in shell formation by inhibiting aragonite formation. Significance: Results of this study suggest a connection between the matrix protein and magnesium.
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