ABSTRACT
This research investigated the effects of different concentrations (0, 0.5, 1.0, 2.0 mmol·L-1) of salicylic acid on the seed germination and physiological characteristics of legume forage Coronilla varia (cultivar 'Lvbaoshi') under PEG-6000 (concentration 8% and 12%) simulated drought stress. The results showed that under drought stress, 0.5-1.0 mmol·L-1 salicylic acid significantly increased germination percentage, germination vigour, germination index, vitality index and bud length of C. varia. Under the stress of 12% PEG, the dry mass of C. varia seedlings processed by 1.0 mmol·L-1 salicylic acid was significantly higher than that under drought stress. 0.5-1.0 mmol·L-1 salicylic acid processing significantly increased proline, soluble protein content, the activities of catalase, peroxidase and superoxide dismutase of C. varia seedlings under drought stress, but cell electrolyte permeability, H2O2 content and O2-· production rate of seedlings were significantly decreased. 1.0 mmol·L-1 salicylic acid produced the best results. When the concentration of salicylic acid was beyond 2.0 mmol·L-1, no mitigation effect was observed on the seed germination and growth of seedlings under drought stress. It was concluded that salicylic acid at appropriate concentrations could effectively improve osmotic regulation, antioxidation and mitigate the damage of drought stress so as to promote the growth of C. varia seedlings.
Subject(s)
Droughts , Germination , Salicylic Acid/pharmacology , Hydrogen Peroxide , Seedlings , Seeds , Stress, PhysiologicalABSTRACT
Avian influenza A viruses (AIVs), including the H5N1, H9N2, and H7N7 subtypes, have been directly transmitted to humans, raising concerns over the possibility of a new influenza pandemic. To prevent a future avian influenza pandemic, it is very important to fully understand the molecular basis driving the change in AIV virulence and host tropism. Although virulent variants of other viruses have been generated by homologous recombination, the occurrence of homologous recombination within AIV segments is controversial and far from proven. This study reports three circulating H9N2 AIVs with similar mosaic PA genes descended from H9N2 and H5N1. Additionally, many homologous recombinants are also found deposited in GenBank. Recombination events can occur in PB2, PB1, PA, HA, and NP segments and between lineages of the same/different serotype. These results collectively demonstrate that intragenic recombination plays a role in driving the evolution of AIVs, potentially resulting in effects on AIV virulence and host tropism changes.
Subject(s)
Evolution, Molecular , Influenza A Virus, H5N1 Subtype/genetics , Influenza A Virus, H7N7 Subtype/genetics , Influenza A Virus, H9N2 Subtype/genetics , Recombination, Genetic , Animals , Chickens , China , Influenza A Virus, H5N1 Subtype/pathogenicity , Influenza A Virus, H7N7 Subtype/pathogenicity , Influenza A Virus, H9N2 Subtype/pathogenicityABSTRACT
Infectious bursal disease virus (IBDV) is a non-enveloped double-stranded RNA virus belonging to the Birnaviridae family. It shows substantial variation in the major antigen region of the viral capsid protein VP2, where a hypervariable region plays a key role in the virulence of IBDV and its epitope. This study identifies several putative recombinants from previously published data to suggest that homologous recombination may naturally occur between different IBDV strains. In addition, a novel very virulence sublineage emerges in the VP2 phylogenic tree, comprising three putative recombination strains isolated in Korea and China, KSH, KK1 and SH-h. The major putative parents of the three mosaics are descended from the vaccine lineage while their hypervariable regions from vvIBDV. These findings also suggest that vaccine coverage may have influence on the evolution and genetic diversity of IBDV, resulting in a novel group with vvIBDV phenotype through recombination with wild IBDV.
Subject(s)
Genetic Variation , Infectious bursal disease virus/genetics , Phylogeny , RNA, Double-Stranded/genetics , Animals , Birnaviridae Infections/epidemiology , Birnaviridae Infections/veterinary , Capsid Proteins/genetics , China , Crossing Over, Genetic , Genotype , Infectious bursal disease virus/classification , Infectious bursal disease virus/isolation & purification , Infectious bursal disease virus/pathogenicity , Korea , Phenotype , Poultry Diseases/epidemiology , Poultry Diseases/virology , RNA, Viral/genetics , Recombination, Genetic , VirulenceABSTRACT
Newcastle disease (ND), caused by ND virus (NDV), is one of the most serious illnesses of birds, particularly chickens, and has been one of the major causes of economic losses in the poultry industry. Live vaccines are widely used to prevent chicken from NDV all over the world. Given the implications that recombination has for RNA virus evolution, it is clearly important to determine the extent to which recombination plays a role in NDV evolution. In this study, we performed the phylogenetic and recombination analysis on complete NDV genomes. A natural multi-recombinant cockatoo/Indonesia/14698/90 (AY562985) was identified. Its two minor parental-like strains might be from the NDV vaccine lineage and anhinga/U.S.(Fl)/44083/93 lineage, respectively. Our study suggests that recombination plays a role in NDV evolution. Especially, the study also suggests that live vaccines have capacity to play roles in shaping NDV evolution by homologous recombination with circulating virus.
