Due to the simplicity and low detection limit, fluorescent probes are widely used in both analytical sensing and optical imaging. Compared to conventional fluorescent probes, reversibility endows the reversible fluorescent probe outstanding advantages and special properties, making reversible fluorescent probes with capable of quantitative, repetitive or circulatory. Reversible fluorescent probes can also monitor the concentration dynamics of target analytes in real time, such as metal ions, proteins and enzymes, as well as intracellular redox processes, which have been widely applied in various fields. This review summarized the types and excellent properties of reversible fluorescent probes designed and developed in recent years. It also summarized the applications of reversible fluorescent probe in fluorescence imaging, biological testing, monitoring redox cycles, and proposed the remaining challenges and future development directions of the reversible fluorescent probe. This review provided comprehensive overview of reversible fluorescent probe, which may provide valuable references for the design and fabrication of the reversible fluorescent probe.

Cysteine-aspartic acid protease (caspases) is a key enzyme during apoptosis. In this study, we cloned the full-length sequence of the Caspase-10 and Caspase-3 gene, analyzed their expression profile in different tissues, and during different developmental stages of Strongylocentrotus intermedius,and finally analyzed their functions. The SiCaspase-10 and SiCaspase-3 in S. intermedius were respectively 3107bp and 1642bp in length, which accordingly possessed open reading frames (ORF) of 2064 and 960bp, encoding 687 and 319 amino acids. A 5’UTR (untranslated region) of 620bp and a 3’UTR of 423bp were cloned in SiCaspase-10, and a 5’UTR of 365bp and a 3’UTR of 317bp in Caspase-3. The predicted molecular weights of Caspase-10 and SiCaspase-3 were 254.7 and 35.34 kDa, and their theoretical pI values were 4.85 and 4.84, respectively. The SiCapsase-10 has conserved features, such as a cysyein as partate-specific catalytic domains, and the SiCaspase-3 also has partate-specific catalytic domains. Our findings demonstrated the expression of SiCaspase-10 and SiCaspase-3 in all the six tissues via tissue-specific expression assays with the significant expression in coelomocyte. According to time-course expression assessments at 9 distinct developmental stages, SiCaspase-10 and SiCaspase-3 has the maximum expression in the 8-cell stage. SiCaspase-3 expression was drastically reduced in the intestines and coelomocyte tissue 48 hours after SiCaspase-10 was knocked down by particular small interfering RNA (siRNA), demonstrating that SiCaspase-3 is Caspase-10's downstream target gene. TUNEL staining analysis of coelomic cells after Sicaspase-3 inhibition showed that the apoptosis rate decreased significantly, which proved that Sicaspase-3 was involved in the apoptotic response. The findings contribute to a better knowledge of the SiCaspase-10 and SiCaspase-3 mediated immune response in S. intermedius, as well as a theoretical experimental foundation for investigating the mechanism of action of SiCaspase-10 and SiCaspase-3 genes and the identification of disease-resistant sea urchin families.

The NOD-like receptor proteins (NLRP) is an important genes primarily involved in innate immunity. In this study, we identified a novel NLRP gene designated as AjNLRP3 (GenBank accession number MF663701) in Apostichopus japonicus using transcriptome sequencing and the rapid amplification of cDNA ends approach. The full-length of AjNLRP3 is 3642 bp and a putative open reading frame of 2424 bp encodes a polypeptide with 807 amino acid residues. The predicted molecular mass of the protein sequence predicted for AjNLRP3 is 93.03 kDa and its theoretical pI is 6.14. AjNLRP3 contains two low complexity regions, two internal repeat regions, and a NACHT domain. Spatial distribution expression analysis detected AjNLRP3 in all of the tissues tested, with greater expression levels in the body wall, moderate expression in the respiratory tree, and weaker levels in the intestine, tube feet, celomocytes, and longitudinal muscle. The expression levels of AjNLRP3 increased by 2.60-fold in the celomocytes and decreased by 0.87-fold in the respiratory tree of diseased sea cucumbers compared with those in healthy sea cucumbers. Time-course expression analysis under bacterial challenge in celomocytes showed that the expression of AjNLRP3 was significantly decreased by 0.23-fold at 8 h and by 0.20-fold at 24 h. In conclusion, this study showed that the AjNLRP3 protein found in the sea cucumber has a similar structure and biological function to that in other organisms, where it appears to be involved with the innate immune responses against bacterial infection.

Mizuhopecten yessoensis, one of the most highly favored scallops on the international market, has suffered from massive summer mortalities. Water temperature is an important environmental stressor which has significant effects on the physiological and biochemical response of scallops. Heat shock protein 90 (HSP90) plays a key role in defense against various environmental stresses that could damage the cellular and molecular structure of cells. In this study, molecular characterization and expression of HSP90 in M. yessoensis (designated MyHSP90) were analyzed as an indicator to understand the mechanisms of heat shock response in M. yessoensis under temperature stress. The full-length sequence of MyHSP90 cDNA (GenBank accession no. MF196912) is composed of 2639 base pair encoding a 726-amino acid polypeptide with a predicted molecular mass of 83.26 kDa. Tissue expression analysis of MyHSP90 genes revealed ubiquitous expression in each tissue examined, and showed a temperature-dependent response, and the expression level was up-regulated significantly in all the six tissues tested (p < 0.05) except gonad. The results will be useful in furthering the understanding of the massive summer mortalities in M. yessoensis under temperature stress. Additionally, MyHSP90 could be used as a potential biomarker in practice to monitor environmental changes in future studies.

Sperm cell and embryo toxicity tests using the sea urchin Strongylocentrotus intermedius (S. intermedius) were performed to assess the toxicity of indoxacarb, a new widely used insecticide. New toxicity data for indoxacarb expressed as median effective concentration (EC50) were reported for the sea urchin species. When sperms and cells were exposed to the pesticide before fertilization, no significant inhibition in the fertilization success of S. intermedius (up to 40 mg/L) was observed. Developmental toxicity of the pesticide displayed a significant dose-related increase of larval malformations and differentiation arrest at concentrations of 0.1 mg/L to 40.0 mg/L at each cleavage, including the 2-cell stage, 4-cell, blastula, gastrula, prism and 4-arm pluteus stages. It seems that 4-arm pluteus is the most sensitive to indoxacarb with the EC50 of 3.73 mg/L, two times less than that of the first cleavage stage. All these results indicate that more attentions should be paid to the potential marine pollutions caused by this pesticide indoxacarb.