FvKex2 is required for development, virulence, and mycotoxin production in Fusarium verticillioides.

Fusarium verticillioides is one of the most important fungal pathogens causing maize ear and stalk rots, thereby undermining global food security. Infected seeds are usually unhealthy for consumption due to contamination with fumonisin B1 (FB1) mycotoxin produced by the fungus as a virulence factor. Unveiling the molecular factors that determine fungal development and pathogenesis will help in the control and management of the diseases. Kex2 is a kexin-like Golgi-resident proprotein convertase that is involved in the activation of some important proproteins. Herein, we identified and functionally characterized FvKex2 in relation to F. verticillioides development and virulence by bioinformatics and functional genomics approaches. We found that FvKex2 is required for the fungal normal vegetative growth, because the growth of the ∆Fvkex2 mutant was significantly reduced on culture media compared to the wild-type and complemented strains. The mutant also produced very few conidia with morphologically abnormal shapes when compared with those from the wild type. However, the kexin-like protein was dispensable for the male role in sexual reproduction in F. verticillioides. In contrast, pathogenicity was nearly abolished on wounded maize stalks and sugarcane leaves in the absence of FvKEX2 gene, suggesting an essential role of Fvkex2 in the virulence of F. verticillioides. Furthermore, high-performance liquid chromatography analysis revealed that the ∆Fvkex2 mutant produced a significantly lower level of FB1 mycotoxin compared to the wild-type and complemented strains, consistent with the loss of virulence observed in the mutant. Taken together, our results indicate that FvKex2 is critical for vegetative growth, FB1 biosynthesis, and virulence, but dispensable for sexual reproduction in F. verticillioides. The study presents the kexin-like protein as a potential drug target for the management of the devastating maize ear and stalk rot diseases. Further studies should aim at uncovering the link between FvKex2 activity and FB1 biosynthesis genes. KEY POINTS: •The kexin-like protein FvKex2 contributes significantly to the vegetative growth of Fusarium verticillioides. •The conserved protein is required for fungal conidiation and conidial morphology, but dispensable for sexual reproduction. •Deletion of FvKEX2 greatly attenuates the virulence and mycotoxin production potential of F. verticillioides.

Nuciferine reduced fat deposition by controlling triglyceride and cholesterol concentration in broiler chickens.

The purpose of this study was to investigate whether dietary nuciferine affects lipid metabolism in broiler chickens. Four treatment groups were made from 120 1-day-old broiler chickens including the base diet group (normal control [NC], supplemented with 0 mg/kg of nuciferine) and groups treated with 25 mg/kg, 100 mg/kg, and 400 mg/kg of dietary nuciferine, which was supplemented for 42 d. The results showed that body weight, average daily weight gain, and absolute and relative fat and liver weight were significantly decreased with nuciferine supplementation. The plasma concentration of triiodothyronine, free triiodothyronine, thyroxine, and free thyroxine was significantly decreased in the nuciferine-supplemented group, but the plasma glucagon concentration was significantly increased. The plasma and hepatic triglyceride (TG) and total cholesterol (TC) concentrations were significantly decreased in the nuciferine group, but plasma and hepatic nonesterified fatty acid concentration, hepatic lipase activity, and hepatic glycogen content were significantly increased. Hepatic histological examination showed that fat cell volume and size in the 100 and 400 mg/kg group were smaller than those in the NC group. The fatty degeneration in the liver was decreased with nuciferine supplementation. The fat cell volume and size were shrunk in the nuciferine group. Dietary nuciferine supplementation significantly decreased the gene expression level of HMGCR, SREBP2, ACC, and SPEBP-1C, but significantly increased the gene expression level of LXR-α, CYP7A1, and CPT-I. The results indicated that nuciferine exhibited strong reduced fat deposition activities and reflected not only by decrease of the concentration of TG and TC but also by reduction in the key gene expression level of HMGCR, SREBP2, ACC, and SPEBP-1c and elevation of the key gene expression level of LXR-α, CYP7A1, and CPT-I. Taken together, our results suggested that the ability of nuciferine on reducing fat deposition in broiler chickens by regulating lipid metabolism was associated with the balance of TG and TC concentration.

Curcumin supplementation regulates lipid metabolism in broiler chickens.

The purpose of this study was to investigate whether dietary curcumin affects lipid metabolism in the liver of broiler chickens. Four treatment groups were formed from 1200 1-day-old broiler chickens, including a base diet (control, supplemented with 0 mg/kg curcumin), 500 mg/kg, 1,000 mg/kg, and 2,000 mg/kg dietary curcumin, for 49 d. At the end of experiment, each group of 50 chickens were sampled and analyzed. Compared with the control group, the results have showed that body weight, average daily weight gain, absolute and relative liver weight significantly decreased in the 1,000 and 2,000 mg/kg curcumin groups (P < 0.05). The absolute and relative abdominal fat weight were significantly decreased in the 2,000 mg/kg curcumin group (P < 0.05). The concentrations of plasma low-density lipoprotein cholesterol (P < 0.05) and plasma and hepatic triglyceride concentrations (P < 0.01) were markedly decreased in the 2,000 mg/kg curcumin group. The hepatic nonesterified fatty acid concentration (P < 0.05) and the hepatic glycogen (P < 0.05) and liver hepatic lipase activities (P < 0.01) were significantly increased in the 1,000 and 2,000 mg/kg curcumin groups. The plasma-free triiodothyronine and thyroxine concentrations were significantly increased in the 2,000 mg/kg curcumin group (P < 0.05). The gene expression levels of fatty acid synthase (FAS) and sterol regulatory element binding protein-1c (SREBP-1c) were significantly decreased in all curcumin groups (P < 0.05), but the gene expression levels of acetyl CoA carboxylase (ACC) and ATP-citrate lyase (ACLY) were significantly decreased only in the 2,000 mg/kg curcumin group (P < 0.05). The expression levels of peroxisome proliferators-activated receptor α (PPARα) and carnitine palmitoyl transferase-I (CPT-I) were significantly increased in the 1,000 and 2,000 mg/kg curcumin groups (P < 0.05). These results indicated that curcumin plays an important role in reduction abdominal fat deposition by decreasing the hepatic and plasma lipid profile and affecting the expression levels of genes related to lipogenesis and lipolysis including ACC, FAS, SREBP-1c, ACLY, PPARα, and CPT-I.

Microbial ecology and association of Bacillus thuringiensis in chicken feces originating from feed.

To explain the association of Bacillus thuringiensis (Bt) with animal feces, an ecological analysis in chickens was conducted by introducing a cry(-) strain marked by production of green fluorescent protein (GFP). After feeding with the tagged Bt strains, the feces of the tested chickens were collected at different times, isolated, and the morphology of Bt was observed. It was shown that Bt strain HD-73GFP in spore form could be isolated from feces of chickens for a period of 13 d, and then it disappeared thereafter. Bt could be detected only up to day 4 (but not thereafter), when chickens were fed with vegetative cells of HD-73GFP. To confirm the source of newly isolated strains, the gfp gene was examined by polymerase chain reaction (PCR), which showed that all the isolated strains harbored the marker gene. Recent data from isolation and PCR had suggested that fecal Bt strains had originated from food. Chicken tissues were thus dissected to isolate Bt strains and to investigate whether Bt could be located in vivo. Bt was located within the duodenum in spore form. Compared to the morphology of the isolated strains at different growth times, the growth rates of all the tested Bt had little changes when passing through the digestive system to the feces. Dissection of the chickens confirmed that Bt was safe for the tested animal.