Dry direct-seeded rice (DDR) sown using a multifunctional seeder that performs synchronous rotary tillage and sowing has received increased attention because it is highly efficient, relatively cheap, and environmentally friendly.  However, this method of rice production may produce lower yields in a rice–wheat rotation system because of its poor seedling establishment.  To address this problem, we performed field experiments to determine the rice yield at five seedling density levels (B1, B2, B3, B4, and B5=100, 190, 280, 370, and 460 seedlings m⁻², respectively) and clarify the physiological basis of yield formation.  We selected a representative high-quality rice variety and a multifunctional seeder that used in a typical rice–wheat rotation area in 2016 and 2018.  The proportion of main stem panicle increased with increasing seedling density.  There was a parabolic relationship between yield and seedling density, and the maximum yield (9.34−9.47 t ha⁻¹) was obtained under B3.  The maximum yield was associated with a higher total spikelet number m⁻² and greater biomass accumulation from heading to maturity.  The higher total spikelet number m⁻² under B3 was attributed to an increase in panicle number m⁻² compared with B1 and B2.  Although the panicle numbers also increased under B4 and B5, these increases were insufficient to compensate for the reduced spikelet numbers per panicle.  Lower biomass, smaller leaf area, and lower N uptake per plant from the stem elongation stage to the heading stage were partially responsible for the smaller panicle size at higher seedling density levels such as B5.  The higher biomass accumulation under B3 was ascribed to the increases in the photosynthetic rate of the top three leaves m⁻² of land, crop growth rate, net assimilation rate, and leaf area index.  Furthermore, the B3 rice population was marked by a higher grain–leaf ratio, as well as a lower export ratio and transport ratio of biomass per stem-sheath.  A quadratic function predicted that 260−290 seedlings m⁻² is the optimum seedling density for achieving maximum yield.  Together, these results suggested that appropriately increasing the seedling density, and thereby increasing the proportion of panicles formed by the main stem, is an effective approach for obtaining a higher yield in DDR sown using a multifunctional seeder in a rice–wheat rotation system.

A bentonite-humic acid (B-HA) mixture added to degraded soils may improve soil physical and hydraulic properties, due to effects such as improved soil structure and increased water and nutrient retention, but its effect on soil physicochemical and biological properties, and grain quality is largely unknown.  The effect of B-HA, added at 30 Mg ha⁻¹, was studied at 1, 3, 5 and 7 years after its addition to a degraded sandy soil in a semi-arid region of China.  The addition of B-HA significantly increased water-filled pore space and soil organic carbon, especially at 3 to 5 years after its soil addition to the soil.  Amending the sandy soil with B-HA also increased the content of microbial biomass (MB)-carbon, -nitrogen and -phosphorus, and the activities of urease, invertase, catalase and alkaline phosphatase.  The significant effect of maize (Zea mays L.) growth stage on soil MB and enzyme activities accounted for 58 and 84% of their total variation, respectively.  In comparison, B-HA accounted for 8% of the total variability for each of the same two variables.  B-HA significantly enhanced soil properties and the uptake of N and P by maize in semi-arid areas.  The use of B-HA product would be an effective management strategy to reclaim degraded sandy soils and foster sustainable agriculture production in northeast China and regions of the world with similar soils and climate.

The nonstructural protein 10 (nsp10) of porcine reproductive and respiratory syndrome virus (PRRSV) encodes for helicase which plays a vital role in viral replication.  In the present study, a truncated form of nsp10, termed nsp10a, was found in PRRSV-infected cells and the production of nsp10a was strain-specific.  Mass spectrometric analysis and deletion mutagenesis indicated that nsp10a may be short of about 70 amino acids in the N terminus of nsp10.  Further studies by rescuing recombinant viruses showed that the Glu-69 in nsp10 was the key amino acid for nsp10a production.  Finally, we demonstrated that nsp10a exerted little influence on the growth kinetics of PRRSV in vitro. 

    Porcine reproductive and respiratory syndrome virus (PRRSV) actively induces cell apoptosis both in vitro and in vivo, which can contribute critically to viral pathogenesis.  Previous studies have shown that the PRRSV nonstructural protein 4 (nsp4) is an important mediator of this process, but the underlying molecular details remain poorly understood.  In this study, we found that the PRRSV nsp4 interacted with the mitochondrial inner membrane protein cytochrome c1 (cyto.c1) and induced its proteolytic cleavage.  Interestingly, the cleaved N-terminal fragment of cyto.c1 was found to exert apoptotic activity, which could cause mitochondrial fragmentation, resulting in apoptotic cell death.  And RNA interference (RNAi) silencing experiments further confirmed the crucial role which cyto.c1 played in nsp4- and PRRSV-induced cell apoptosis.  Thus, our data provide an important piece of mechanistic clues for PRRSV-induced cell apoptosis and also elucidate a novel mechanism for the 3C-like proteases in this finding. 

   The glycoprotein 5 (GP5) of porcine reproductive and respiratory syndrome virus (PRRSV) is a multi-functional protein that plays important roles in virus assembly, entry and viral anti-host responses. In the present study, we investigated the cellular binding partners of GP5 by using lentivirus transduction coupled with immunoprecipitation and mass spectrometry. There were about 40 cellular proteins identified with high Confidence Icons by MS/MS. Ingenuity Pathway Analysis (IPA) indicated that these proteins could be assigned to different functional classes and networks. Furthermore, we validated some of the interactions by co-immunoprecipitation (Co-IP) and confocal microscopy, including those with mitofilin, a mitochondrial inner membrane protein that might be involved in PRRSV or GP5-induced apoptosis, and calnexin, a protein chaperone that might facilitate the folding and maturation of GP5. The interactome data contribute to understand the role and molecular mechanisms of GP5 in PRRSV pathogenesis.