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Carbonic anhydrases (CAs) are ubiquitous zinc metalloenzymes that catalyze the interconversion of carbon dioxide and bicarbonate. Higher plants mainly contain the three evolutionarily distinct CA families αCA, βCA, and γCA, with each represented by multiple isoforms. Alternative splicing (AS) of the CA transcripts is common. However, there is little information on the spliced variants of individual CA isoforms. In this study, we focused on the characterization of spliced variants of βCA1 from Arabidopsis. The expression patterns and subcellular localization of the individual spliced variants of βCA1 were examined. The results showed that the spliced variants of βCA1 possessed different subcellular and tissue distributions and responded differently to environmental stimuli. Additionally, we addressed the physiological role of βCA1 in heat stress response and its protein-protein interaction (PPI) network. Our results showed that βCA1 was regulated by heat stresses, and βca1 mutant was hypersensitive to heat stress, indicating a role for βCA1 in heat stress response. Furthermore, PPI network analysis revealed that βCA1 interacts with multiple proteins involved in several processes, including photosynthesis, metabolism, and the stress response, and these will provide new avenues for future investigations of βCA1.

The main purpose of the present study was undertaken to isolate bioactive substances from microbial secondary metabolites of Streptomyces gilvosporeu AXY-25 and to determine their antiparasitic effect against Ichthyophthirius multifiliis. A pure compound showing strong anti- I. multifiliis activity was isolated from a culture of S. gilvosporeu AXY-25 by using the method of bioassay-guided isolation. The chemical structure of the active compound was confirmed as natamycin (NAT) by spectral analysis (EI-MS, 1H NMR and 13C NMR). An in vitro anti-parasitic assay demonstrated that 100% of theronts were killed with a concentration of 25.0 mg L−1 NAT for 4 h with an effective concentration (EC50) (95% CI) at 10.9 (10.7–11.1) mg L−1. Similiary, all tomonts were killed by a dose of 25.0 mg L−1. An in vivo anti-parasitic assay showed that the number of I. multifiliis trophonts on the surface of hybrid Erythroculter ilishaeformis in the NAT-treated group were markedly lower when compared to the control group (p

The present study was undertaken to investigate the antiparasitic activity of extracellular products of Streptomyces albus. Bioactivity-guided isolation of chloroform extracts affording a compound showing potent activity. The structure of the compound was elucidated as salinomycin (SAL) by EI-MS, 1H NMR and 13C NMR. In vitro test showed that SAL has potent anti-parasitic efficacy against theronts of Ichthyophthirius multifiliis with 10 min, 1, 2, 3 and 4 h (effective concentration) EC50 (95% confidence intervals) of 2.12 (2.22–2.02), 1.93 (1.98–1.88), 1.42 (1.47–1.37), 1.35 (1.41–1.31) and 1.11 (1.21–1.01) mg L−1. In vitro antiparasitic assays revealed that SAL could be 100% effective against I. multifiliis encysted tomonts at a concentration of 8.0 mg L−1. In vivo test demonstrated that the number of I. multifiliis trophonts on Erythroculter ilishaeformis treated with SAL was markedly lower than that of control group at 10 days after exposed to theronts (P < 0.05). In the control group, 80% mortality was observed owing to heavy I. multifiliis infection at 10 days. On the other hand, only 30.0% mortality was recorded in the group treated with 8.0 mg L−1 SAL. The median lethal dose (LD50) of SAL for E. ilishaeformis was 32.9 mg L−1.

Background In recent years, crucian carp hematopoietic necrosis caused by Cyprinid herpesvirus 2 (CyHV-2) infection has caused an enormous economic loss to the aquaculture industry. Methods In this study antigenic epitope analysis was performed on the membrane proteins of CyHV-2, and 8 antigen-rich peptide fragments were selected for prokaryotic expression. Then, the immunogenicity of the recombinant proteins was analyzed. On this basis, DNA vaccines were constructed for immunization of hybridized Prussian carps. The protective effect of DNA vaccines against challenge in hybridized Prussian carps was evaluated. Results The results showed that all 8 recombinant proteins were successfully expressed. Among the recombinant proteins, ORF16, tORF25, tORF64, and ORF146, gave a positive serum reaction with CyHV-2. Of the four proteins used for the immunization of silver crucian carps, the antibody titer induced by tORF25 was the highest. The DNA vaccine, pEGFP-N1-ORF25, was constructed based on ORF25 and able to induce production of specific antibodies in carps, while up-regulating the expression of MHCⅠ, IL-1β, C3, and TF-A in the kidneys of carps. Moreover, the immunoprotective rate was increased to 70% in hybridized Prussian carps. Conclusion The results showed that the DNA vaccine constructed based on the ORF25 gene had a greater immune protective effect and can be used as a candidate vaccine for immunoprotection against CyHV-2.

Saprolegnia infections cause severe economic losses among freshwater fish farming. In this study, two known compounds, rhein and aloe-emodin, were isolated from Rheum palmatum, and the in vitro inhibitory activity of both compounds against mycelial growth and spore germination of Saprolegnia was tested. Both rhein and aloe-emodin were able to decrease Saprolegnia mycelial growth and spore activity in all tested concentrations after exposure for 48 h. Complete inhibition of mycelial growth was observed at 20 mg/L for rhein and at 50 mg/L for aloe-emodin, while spore germination was 100% prevented at 16 and 40 mg/L for rhein and aloe-emodin, respectively. Because rhein showed stronger in vitro anti-Saprolegnia activity, it was further tested in vivo to measure the prevention and treatment efficacy on Saprolegnia infection of grass carp. Its acute activity to grass carp was also evaluated. The results revealed that exposure to rhein at 20 mg/L for 7 d could prevent 93.3% of infections by Saprolegnia in abraded grass carp, while 67.7% of infected fish could be recovered by treatment with rhein. The 48-h median lethal concentration (48 h-LC50) to grass carp was 148.5 mg/L, which is about 7.4 times the effective dose indicating the safety for the use of rhein. This study suggests that rhein has promising anti-Saprolegnia activity and may be an option in preventing and controlling Saprolegnia infection.