Nitrogen fertilization compensation the weak photosynthesis of Oilseed rape (Brassca napus L.) under haze weather.

Haze and cloudy weather reduce photo-synthetically active radiation (PAR), which affects the formation of crop yield and nitrogen (N) fertilizer utilization.. We conducted field trails in normal year and severe winter haze year, aiming to compare the difference of photosynthesis and N uptake in winter rapeseed under different N levels. Daily sunshine hours and averaged radiation intensity in winter haze year decreased by 54.1% and 33.3% respectively as compared with the past 30 years. Diurnal variation of net photosynthetic rate in winter haze day was 16.2% lower than that of sunny day. Leaf area and photosynthetic capacity decreased significantly during winter haze year. The shoot biomass and N uptake at the rosette stage accounted for only 9.6% and 26.6% of the total growth period in winter haze year, while 24.4% and 70.5% in normal year, respectively. However, in winter haze year, as the top dressing of N application increasing after the rosette stage, shoot biomass increased gradually. In order to achieve the target yield of 2.5 t ha-1, after suffering winter haze, it is necessary to apply additional 73.1 kg N ha-1. In conclusion, the haze climate reduced the radiation intensity and stability, leading to a decline in photosynthetic productivity in winter oilseed rape. Applying higher N fertilizer after winter haze can compensate the negative influence and ensure rapeseed yield.

Assessing the efficacy of a live vaccine against avian encephalomyelitis virus.

Avian encephalomyelitis virus (AEV) causes typical neurological symptoms in young chicks and a transient drop in egg production and hatchability in adult laying birds, resulting in huge economic losses in the poultry industry. An effective way to control and prevent this disease is vaccination of the flocks. Here, we assessed the efficacy of the live vaccine candidate strain GDt29 against avian encephalomyelitis virus. The GDt29 strain has low virulence, was confirmed safe, and showed no signs of pathogenicity. High titers of AEV-specific antibodies were detected in GDt29-vaccinated hens (S/P > 3.0) and their progeny (S/P > 2.0). Moreover, the eggs of GDt29-vaccinated hens with high levels of maternal antibodies were hatched successfully regardless of challenge with a heterologous AEV strain, and the GDt29 attenuated vaccine showed higher protective efficacy against AEV than the commercial vaccine. Furthermore, contact-exposed chicks bred with GDt29-vaccinated birds generated high titers against AE virus (S/P > 2.8). Collectively, our studies are proof of the principle that GDt29 might be an ideal vaccine candidate to prevent AEV infection, and they highlight the utility of using a live vaccine against AEV.

Efficacy of an autophagy-targeted DNA vaccine against avian leukosis virus subgroup J.

Infection with the avian leukosis virus subgroup J (ALV-J) can lead to neoplastic disease in chickens, inflicting significant economic losses to the poultry industry. Recent reports have identified inhibitory effects of ALV-J on autophagy, a process involving in innate and adaptive immunity. Inspired by this connection between autophagy and immunity, we developed a novel DNA vaccine against ALV-J which includes co-administration of rapamycin to stimulate autophagy. To measure the efficacy of the developed prototype vaccine, five experimental groups of seven-day-old chickens was immunized three times at three-week intervals respectively with vector, pVAX1-gp85, pVAX1-gp85-LC3, pVAX1-gp85+rapamycin and pVAX1-gp85-LC3+rapamycin through electroporation. We then tested their antibody titers, cytokine levels and cellular immune responses. The immunoprotective efficacy of the prototype vaccines against the challenge of the ALV-J GD1109 strain was also examined. The results showed that the combination of pVAX1-gp85-LC3 and rapamycin was able to induce the highest antibody titers, and enhance interleukin(IL)-2, IL-10 and interferon (IFN)-γ expression, and the chickens immunized with the combination of pVAX1-gp85-LC3 and rapamycin showed the highest percentage of CD3+CD8+T lymphocytes. Based on our results, we suggest that stimulating autophagy can improve the efficacy of DNA vaccines and that our DNA vaccine shows the potential of being a candidate vaccine against ALV-J. This study provides a novel strategy for developing vaccines against ALV-J.

GADD45ß, an anti-tumor gene, inhibits avian leukosis virus subgroup J replication in chickens.

Avian leukosis virus subgroup J (ALV-J) is a retroviruses that induces neoplasia, hepatomegaly, immunosuppression and poor performance in chickens. The tumorigenic and pathogenic mechanisms of ALV-J remain a hot topic. To explore anti-tumor genes that promote resistance to ALV-J infection in chickens, we bred ALV-J resistant and susceptible chickens (F3 generation). RNA-sequencing (RNA-Seq) of liver tissue from the ALV-J resistant and susceptible chickens identified 216 differentially expressed genes; 88 of those genes were up-regulated in the ALV-J resistant chickens (compared to the susceptible ones). We screened for significantly up-regulated genes (P < 0.01) of interest in the ALV-J resistant chickens, based on their involvement in biological signaling pathways. Functional analyses showed that overexpression of GADD45ß inhibited ALV-J replication. GADD45ß could enhance defense against ALV-J infection and may be used as a molecular marker to identify ALV-J infections.

Anatomical variation of mesophyll conductance under potassium deficiency has a vital role in determining leaf photosynthesis.

Leaves exposed to potassium (K) deficiency usually present decreased mesophyll conductance (gm ) and photosynthesis (A). The relative contributions of leaf anatomical traits in determining gm have been quantified; however, anatomical variabilities related to low gm under K starvation remain imperfectly known. A one-dimensional model was used to quantify anatomical controls of the entire CO2 diffusion pathway resistance within a leaf on two Brassica napus L. cultivars in response to K deficiency. Leaf photosynthesis of both cultivars was significantly decreased under K deficiency in parallel with down-regulated gm . The mesophyll conductance limitation contributed to more than one-half of A decline. The decreased internal air space in K-starved leaves was associated with the increase of gas-phase resistance. Potassium deficiency reduced liquid-phase conductance by decreasing the exposed surface area of chloroplasts per unit leaf area (Sc /S), and enlarging the resistance of the cytoplasm that can be interpreted by the increasing distance of chloroplast from cell wall, and between adjacent chloroplasts. Additionally, the discrepancies of A between two cultivars were in part because of gm variations, ascribing to an altered Sc /S. These results emphasize the important role of K on the regulation of gm by enhancing Sc /S and reducing cytoplasm resistance.