The guanine nucleotide-binding protein α subunit protein ChGnaq positively regulates Hsc70 transcription in Crassostrea hongkongensis

Genome-wide identification and expression analysis of C3H gene family in melon

Zinc finger protein (ZFP) represent a significant class of transcription factors in plants, involved in various functions, including tissue development, signal transduction, and responses to both biotic and abiotic stresses. ZFPs are categorized into 10 distinct subfamilies, among which the C3H gene family is recognized as a functionally significant group of transcription factors.To date, no studies have been reported regarding the C3H gene family in melon (Cucumis melo). In this study, 38 CmC3H genes were identified in the melon genome, and these genes are unevenly distributed across the 12 chromosomes. Phylogenetic analysis classified the C3H family members into four groups, with significant differences observed in sequence, protein motifs, and gene structure among CmC3H genes within the same group. The CmC3H family contains one pair of segmentally duplicated genes and shares 20, 7, 39, and 38 pairs of homologous C3H genes with Arabidopsis thaliana, rice (Oryza sativa), cucumber (Cucumis sativus), and watermelon (Citrullus lanatus), respectively. Promoter region analysis revealed a high abundance of cis-elements associated with growth and development, hormone regulation, and stress responses. Expression profiling revealed that CmC3H family members exhibit significant tissue-specific expression patterns. Quantitative PCR analysis indicated that six genes (CmC3H4, CmC3H7, CmC3H13, CmC3H24, CmC3H33, and CmC3H38) may play roles in melon's drought stress resistance. Heavy metal lead stress appears to suppress the expression of CmC3H genes. The genes CmC3H24 and CmC3H33 may be involved in regulating melon's resistance to Fusarium wilt infection. CmC3H11 and CmC3H21 can be considered as the key candidate genes for improving the melon's ability to resist both biotic and abiotic stresses.This study provides preliminary insights into the expression profiles of CmC3H genes under drought stress, heavy metal lead stress, and Fusarium wilt infection, offering a theoretical foundation for the molecular mechanisms underlying melon improvement and stress resistance.

Establishment and application of TaqMan probe-based quantitative real-time PCR for rapid detection and quantification of Ichthyophthirius multifiliis in farming environments and fish tissues

Ichthyophthirius multifiliis, a pathogenic ciliate, is a crucial pathogen of freshwater fish and can result in severe economic loss in the aquaculture industry worldwide. It is necessary to develop a sensitive and accurate method for detecting I. multifiliis in farming environments and fish skin and gills to protect fishes from infection of the parasite due to a lack of both safe and effective treatment drugs. The present study established a new TaqMan probe-based quantitative PCR (qPCR) detection method targeting the coding region of the cathepsin L cysteine protease (ICP2) gene of I. multifiliis. The sensitivity, specificity, reproducibility and application for detection and diagnosis of the TaqMan probe-based qPCR method were evaluated. In addition, the linear model between the cycle threshold (Ct) and the logarithmic starting quantity (SQ) of the number of theronts per 1 L of sterile water was developed as Ct = -3.312lg(SQ)+ 34.47 with an R2 of 0.9636 and a minimum detection limit of 4 theronts per 1 L of water and could be employed to determine the theront number based on Ct value. The results of the detection of trial infection samples with the TaqMan probe-based qPCR method showed that the tissues of fish individuals infected with I. multifiliis and the tank water samples were positive detection signals. In contrast, the tissues and water samples from uninfected fish individuals and tanks containing healthy fish showed no signals. The detection results demonstrated the reliability of this detection method. Overall, the novel TaqMan probe-based qPCR method with high sensitivity and specificity as well as repeatability for detection of I. multifiliis was a valuable tool in detecting the parasite in farming water, pond sediments, and fish tissues and could provide early warning for prevention of the disease caused by I. multifiliis.

The transcriptional factor GATA-4 negatively regulates Hsp70 transcription in Crassostrea hongkongensis

To better explore the application potential of heat shock protein Hsp70s in diverse areas including biomonitoring, a further investigation of the details of the regulatory mechanism governing Hsp70 transcription is required. A transcriptional factor ChGATA-4 that displayed affinity to the ChHsp70 promoter of Crassostrea hongkongensis was isolated and identified by DNA affinity purification as well as mass spectrometry analysis. The ChGATA-4 cDNA is 2162 bp in length and the open reading frame encodes a polypeptide containing 482 amino acids with a conserved zinc finger domain. The over-expression of ChGATA-4 significantly inhibited the expression of ChHsp70 promoter in heterologous HEK293T cells. However, the depletion of ChGATA-4 mRNA by RNAi technique resulted in significant increase of ChHsp70 transcription in oyster hemocytes. The RT-PCR results demonstrated that the transcription of both ChHsp70 and ChGATA-4 were induced by heat, Cd, or NP (Nonyl phenol) stress. This suggested a potential correlation between ChHsp70 and ChGATA-4 in the stress-mediated genetic regulatory cascade. This study demonstrated that ChGATA-4 acts in a negative manner in controlling ChHsp70 transcription in C. hongkongensis and promotes to further understand the mechanisms leading Hsp70 transcription.

Functional characterization of interferon regulatory factor 2 and its role in the transcription of interferon a3 in golden pompano Trachinotus ovatus (Linnaeus 1758)

Similar to mammals, fish possess interferon (IFN) regulatory factor 2 (IRF2)-dependent type I IFN responses. Nevertheless, the detailed mechanism through which IRF2 regulates type I IFNa3 remains largely unknown. In the present study, we first identified two genes from golden pompano (Trachinotus ovatus), IRF2 (ToIRF2) and IFNa3 (ToIFNa3), in the IFN/IRF-based signalling pathway. The open reading frame (ORF) sequence of ToIRF2 encoded 335 amino acids possessing four typical characteristic domains, including a conserved DNA-binding domain (DBD), an interferon association domain 2 (IAD2), a transcriptional activation domain (TAD), and a transcriptional repression domain (TRD). Furthermore, transcripts of ToIRF2 were significantly upregulated after stimulation by polyinosinic: polycytidylic acid [poly (I:C)], lipopolysaccharide (LPS) and flagellin in immune-related tissues (blood, liver, and head-kidney). Moreover, to investigate whether ToIRF2 was a regulator of ToIFNa3, promoter analysis was performed. The results showed that the region from -896 bp to -200 bp is defined as the core promoter using progressive deletion mutations of IFNa3. Additionally, ToIRF2 overexpression led to a clear time-dependent enhancement of ToIFNa3 promoter expression in HEK293T cells. Mutation analyses indicated that the activity of the ToIFNa3 promoter significantly decreased after targeted mutation of M4/5 binding sites. Electrophoretic mobile shift assays (EMSAs) verified that IRF2 interacted with the binding site of the ToIFNa3 promoter region to regulate ToIFNa3 transcription. Last, the promoter activity of ToIFNa3-2 was more responsive to treatment with poly (I:C) than LPS and flagellin. Furthermore, overexpression of ToIRF2 in vitro obviously increased the expression of several IFN/IRF-based signalling pathway genes after poly (I:C) abduction. In conclusion, the present study provides the first evidence of the positive regulation of ToIFNa3 transcription by ToIRF2 and contributes to a better understanding of the transcriptional mechanisms of ToIRF2 in fish.

The Transcriptional Factor PPARαb Positively Regulates Elovl5 Elongase in Golden Pompano Trachinotus ovatus (Linnaeus 1758)

The nuclear peroxisome proliferator-activated receptors (PPARs) regulate the transcription of elongases of very long-chain fatty acids (Elovl), which are involved in polyunsaturated fatty acid (PUFA) biosynthesis in mammals. In the present study, we first characterized the function of Elovl5 elongase in Trachinotus ovatus. The functional study showed that ToElovl5 displayed high elongation activity toward C18 and C20 PUFA. To investigate whether PPARαb was a regulator of Elovl5, we also reported the sequence of T. ovatus PPARαb (ToPPARαb). The open reading frame (ORF) sequence encoded 469 amino acids possessing four typical characteristic domains, including an N-terminal hypervariable region, a DNA-binding domain (DBD), a flexible hinge domain and a ligand-binding domain (LBD). Thirdly, promoter activity experiments showed that the region from PGL3-basic-Elovl5-5 (-146 bp to +459 bp) was defined as the core promoter by progressive deletion mutation of Elovl5. Moreover, PPARαb overexpression led to a clear time-dependent enhancement of ToElovl5 promoter expression in HEK 293T cells. Fourth, the agonist of PPARαb prominently increased PPARαb and Elovl5 expression, while PPARαb depletion by RNAi or an inhibitor was correlated with a significant reduction of Elovl5 transcription in T. ovatus caudal fin cells (TOCF). In conclusion, the present study provides the first evidence of the positive regulation of Elovl5 transcription by PPARαb and contributes to a better understanding of the transcriptional mechanism of PPARαb in fish.