Different responses of Sinorhizobium sp. upon Pb and Zn exposure: Mineralization versus complexation.

Lead (Pb) and zinc (Zn) have been discharged into environment and may negatively impact ecological security. Rhizobia has gained attention due to their involvement in the restoration of metal polluted soils. However, little is known about the responses of rhizobia under Pb and Zn stress, especially the roles played by extracellular polymeric substances (EPS) in the resistance of these two metals. Here, Sinorhizobium sp. C10 was isolated from soil around a mining area and was exposed to a series of Pb/Zn treatments. The cell morphology and surface mineral crystals, EPS content and fluorescent substances were determined. In addition, the extracellular polysaccharides and proteins were characterized by attenuated total reflection infrared spectroscopy (ATR-IR) and X-ray photoelectron spectroscopy (XPS). The results showed that Zn stress induced the synthesis of EPS by C10 cells. Functional groups of polysaccharides (CO) and proteins (C-O/C-N) were involved in complexation with Zn. In contrast, C10 resisted Pb stress by forming lead phosphate (Pb3(PO4)2) on the cell surface. Galactose (Gal) and tyrosine played key roles in resistance to the Zn toxicity, whereas glucosamine (N-Glc) was converted to glucose in large amounts during extracellular Pb precipitation. Together, this study demonstrated that C10 possessed different strategies to detoxify the two metals, and could provide basis for bioremediation of Pb and Zn polluted sites.

[Strategies for exogenous RNA delivery in RNAi-mediated pest management].

Plant diseases and insect pests threaten the safety of crop production greatly. Traditional methods for pest management are challenged by the problems such as environmental pollution, off-target effects, and resistance of pathogens and insects. New biotechnology-based strategies for pest control are expected to be developed. RNA interference (RNAi) is an endogenous process of gene regulation, which has been widely used to study the gene functions in various organisms. In recent years, RNAi-based pest management has received increasing attention. The effective delivery of the exogenous interference RNA into the targets is a key step in RNAi-mediated plant diseases and pest control. Considerable advances were made on the mechanism of RNAi, and various RNA delivery systems were developed for efficient pest control. Here we review the latest advances on mechanisms and influencing factors of RNA delivery, summarize the strategies of exogenous RNA delivery in RNAi-mediated pest control, and highlight the advantages of nanoparticle complexes in dsRNA delivery.

MoDHX35, a DEAH-Box Protein, Is Required for Appressoria Formation and Full Virulence of the Rice Blast Fungus, Magnaporthe oryzae.

The DExD/H-box protein family encompasses a large number of RNA helicases that are involved in RNA metabolism and a variety of physiological functions in different species. However, there is limited knowledge of whether DExD/H-box proteins play a role in the pathogenicity of plant fungal pathogens. In the present work, the DExD/H-box protein MoDHX35, which belongs to the DEAH subfamily, was shown to be crucial in appressoria formation and full virulence of the rice blast fungus, Magnaporthe oryzae. The predicted protein sequence of MoDHX35 had typical DEAH-box domains, showed 47% identity to DHX35 in Homo species, but had no orthologs in Saccharomyces cerevisiae. Deletion of the MoDHX35 gene resulted in reduced tolerance of the mutants to doxorubicin, a nucleic acid synthesis disturbing agent, suggesting the involvement of MoDHX35 in RNA metabolism. MoDHX35-deleted mutants exhibited normal vegetative growth, conidia generation and conidial germination, but showed a reduced appressorium formation rate and attenuated virulence. Our work demonstrates the involvement of DEAH-box protein functions in the pathogenicity of plant fungal pathogens.