The pea aphid, Acyrthosiphon pisum, has an incomplete immune system compared to those of other insect species; some conserved components and pathways in other species are missing in its genome. As a core component of the insect immune system, prophenoloxidase (PPO) genes are retained in the pea aphid. Early studies have also shown the presence of phenoloxidase activity in specific tissues or cells in the pea aphid and suggested its involvement in response to immune challenges. In this study, we knocked down the expression of PPO genes in the pea aphid using double-stranded RNA-based interference, and quantitative PCR analysis and an enzyme activity assay confirmed our success in the PPO gene knockdown. In bacterial and fungal infection experiments, we observed that the knockdown of PPO resulted in more live bacterial cells and fungal spores in the body of the aphids and higher mortality of the aphids after infection. Our study provides evidence supporting a critical role of PPO in the defence of the pea aphid.
A method was depicted to identify null allele CSN1S1 N and low allele CSN1S1 F of the CSN1S1 gene of goat using PCR-SSCP (polymerase chain reaction-single strand conformation polymorphism). First, primer A was designed to amplify the exon 9 of CSN1S1 gene which produced three genotypes AA, AB, and BB. Among these three genotypes, only AA and AB individuals had a cytosine deletion at exon 9 after DNA sequencing, which cannot be used to identify the N and F alleles. Therefore, primer B was used to amplify intron 14 of CSN1S1 of described AA and AB individuals. Genotypes FF, FN and NN were detected within AA individuals and genotypes FO and NO were detected in the above AB individuals. The frequencies of F and N alleles in 708 samples from Xinong Saanen (XS) and Guanzhong (GZ) dairy goat breeds were 0.1139, 0.0927, and 0.2376, 0.1193, respectively. In 268 XS samples, the individuals with NN genotype contained a significant lower protein content than that of other genotypes (P<0.01). Individuals of FF genotype had significant higher milk yield than that of NO genotype in the first milk lactation of 202 XS individuals (P<0.05). Therefore, the variability at CSN1S1 locus contains enough genetic diversity to be potentially useful in improving the quality and production of milk in Chinese dairy goat breeds.
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