Zhideng Lin

Δ9 fatty acyl desaturase (Δ9 FAD) exerts important regulatory effects on fatty acid metabolism and membrane fluidity. However, its existence and the effects of nutritional regulation and ambient salinity on its expression are currently unknown in mud crab (Scylla paramamosain). In this study, the full cDNA sequence of Δ9 fad was isolated from the hepatopancreas of mud crab, which consists of 1468 bp and encodes a polypeptide of 347 amino acids. Sequence analysis revealed that the protein possessed typical characteristics of Δ9 FAD including three histidine-rich domains (HRLWSH, HRVHH and HNYHH), four transmembrane regions and three conserved motifs (FFSHMGW, QRKYY and PWDY). The results of tissue distribution indicated that the mud crab’s Δ9 fad expression was enriched in the hepatopancreas, with relatively lower levels found in the thoracic ganglia and cranial ganglia. Δ9 fad expression in the hepatopancreas was significantly influenced by dietary fatty acid profiles, and the replacement of fish oil with soybean oil markedly downregulated the transcriptional levels of hepatopancreatic Δ9 fad. Furthermore, the transcriptional levels of Δ9 fad were also significantly affected by ambient salinity. Under chronic salinity stress, the 7‰, 12‰, 17‰ and 22‰ salinity groups showed higher transcriptional levels of Δ9 fad in the hepatopancreas than the 27‰ salinity group, and the 7‰ salinity group significantly differed from the 27‰ salinity group. Under the acute salinity stress condition, the Δ9 fad transcriptional levels of muscle in the 14‰ and 4‰ salinity groups were higher than those in the 24‰ salinity group at 6 h and 12 h. By contrast, Δ9 fad in the hepatopancreas exhibited a slow response in reaction to low salinity stress, and only the 4‰ salinity group at 96 h had a higher value than the 24‰ salinity group. In addition, as for the starvation stress experiment, Δ9 fad expression in the starvation group was dramatically reduced when compared with the feeding group. These findings improve our understanding of the physiological roles of Δ9 fad and its regulatory mechanisms in crustaceans.

Visceral white spot disease caused by Pseudomonas plecoglossicida poses a severe threat to large yellow croaker (Larimichthys crocea) aquaculture. This study investigated the immunomodulatory effects and underlying mechanisms of Pseudostellaria heterophylla extract against P. plecoglossicida infection in L. crocea. Fish were fed a basal diet supplemented with 1% P. heterophylla extract for 30, 45, and 60 days, followed by intraperitoneal injection with 200 μL P. plecoglossicida (1 × 10⁴ CFU/mL). When the control group reached about 50% mortality, transcriptome sequencing of head kidney tissues was performed on the 45 and 60 days post-feeding of the treatment groups to analyze gene expression changes following bacterial infection. Survival rates of the treatment groups were 33.33%, 13.33%, and 20% higher than those of the control group at 30, 45, and 60 days post-feeding, respectively. Transcriptomic analysis revealed time-dependent transcriptional responses: in one group, 45 days post-feeding, 10 differentially expressed genes (DEGs) were identified (2 up-regulated and 8 down-regulated), whereas in another group, 60 days post-feeding, 893 DEGs were detected (417 up-regulated and 476 down-regulated). Functional enrichment analysis (GO, KEGG, and GSEA) demonstrated that DEGs were significantly enriched in immune-related pathways, including Toll-like receptor signaling, chemokine activity, Th1 and Th2 cell differentiation, hematopoietic cell lineage, and cytokine–cytokine receptor interaction. Key immune genes, including chemokines, Toll-like receptors, and T cell regulators, were significantly up-regulated. These findings indicate that P. heterophylla extract enhances both the specific and non-specific immune capabilities of L. crocea in a time-dependent manner, with prolonged supplementation eliciting more robust transcriptional activation of immune defense pathways. This study provides a scientific foundation for developing immunological prevention strategies against P. plecoglossicida infection in aquaculture.

The present study investigates the effects of dietary phosphatidylcholine (PC) deficiency and its addition on growth and physiological and biochemical indicators of juvenile Eriocheir sinensis under different oil sources. There were no significant differences in the growth and feed utilization between the vegetable oils and fish oil (FO) groups under PC‐devoid conditions. In contrast, the FO and perilla oil (PO) groups showed better growth‐promoting effects and higher feed utilization than the safflower oil (SO) and olive oil (OO) groups under 3% PC‐added condition. Both dietary PC and oil sources (FO or PO) could inhibit lipid accumulation of the whole crab, and dietary PC also observably facilitated whole‐body protein deposition. In addition, dietary FO and PO increased the burden of the antioxidant system and the risk of lipid peroxidation in juvenile E. sinensis . Meanwhile, diets supplemented with PC effectively alleviated oxidative stress and lipid peroxidation caused by dietary FO and PO. The composition of fatty acids in muscle and hepatopancreas was positively associated with that in diets. Compared with SO and OO, FO and PO significantly reduced the lipid deposition in the hepatopancreas at 3% PC supplementation, possibly because FO and PO formed new physiological‐active PC contained n‐3 polyunsaturated fatty acids (PUFAs) with dietary PC through activating PC remodeling reaction, and promoting fatty acid utilization, and finally inhibiting the lipid accumulation in the hepatopancreas. This study indicates that FO and PO are better lipid sources (LSs) for E. sinensis , providing alternative oil sources in the crab diet in combination with PC supplementation.

Tea is an important cash crop worldwide, and its nutritional value has led to its high economic benefits. Tea anthracnose is a common disease of tea plants that seriously affects food safety and yield and has a far-reaching impact on the sustainable development of the tea industry. In this study, phenotypic analysis and pathogenicity analysis were performed on knockout and complement strains of HTF2—the transcriptional regulator of tea anthracnose homeobox—and the pathogenic mechanism of these strains was explored via RNA-seq. The MoHox1 gene sequence of the rice blast fungus was indexed, and the anthracnose genome was searched for CfHTF2. Evolutionary analysis recently reported the affinity of HTF2 for C. fructicola and C. higginsianum. The loss of CfHTF2 slowed the vegetative growth and spore-producing capacity of C. fructicola and weakened its resistance and pathogenesis to adverse conditions. The transcriptome sequencing of wild-type N425 and CfHTF2 deletion mutants was performed, and a total of 3144 differentially expressed genes (DEGs) were obtained, 1594 of which were upregulated and 1550 of which were downregulated. GO and KEGG enrichment analyses of DEGs mainly focused on signaling pathways such as the biosynthesis of secondary metabolites. In conclusion, this study lays a foundation for further study of the pathogenic mechanism of tea anthracnose and provides a molecular basis for the analysis of the pathogenic molecular mechanism of CfHTF2.