Meloidogyne incognita is a devastating plant-parasitic nematode.  Effectors play important roles during the stages of nematodes infection and parasitism, but their molecular functions remain largely unknown.  In this study, we characterized a new effector, Minc03329, which contains signal peptide for secretion and a C-type lectin domain.  The yeast signal sequence trap experiments indicated that the signal peptide of Minc03329 is functional.  In situ hybridization showed that Minc03329 was specifically expressed in the subventral esophageal gland.  Real-time qPCR confirmed that the expression level of Minc03329 transcript was significantly increased in pre-parasitic and parasitic second-stage juveniles (pre-J2s and par-J2s).  Tobacco rattle virus (TRV)-mediated gene silencing of Minc03329 in host plants largely reduced the pathogenicity of nematodes.  On the contrary, ectopic expression of Minc03329 in Arabidopsis thaliana significantly increased plant susceptibility to nematodes.  Transient expression of Minc03329 in Nicotiana benthamiana leaves suppressed the programmed cell death triggered by the pro-apoptotic protein BAX.  Moreover, the transcriptome analysis of Minc03329-transgenic Arabidopsis and wild type revealed that many defense-related genes were significantly down-regulated.  Interestingly, some different expressed genes were involved in the formation of nematode feeding sites.  These results revealed that Minc03329 is an important effector for M. incognita, suppressing host defense response and promoting pathogenicity.

    The effect of long-term fertilization on soil denitrifying communities was analysed by measuring the abundance and diversity of the nitrous oxide (N₂O) reductase gene, nosZ.  Soil samples were collected from plots of a long-term fertilization experiment established in 1982 in Suining City, China.  The fertilizer treatments were no fertilizer (CK), three chemical fertilizer (CF) treatments (N, NP, NPK), manure (M) alone, and manure with chemical fertilizers (NM, NPM, NPKM).  The abundance and diversity of the denitrifying bacteria were assessed by real-time quantitative PCR, terminal restriction fragment length polymorphism (T-RFLP), and cloning and sequencing of nosZ genes.  The diversity and abundance of nosZ-denitrifiers was higher in soil amended with manure and chemical fertilizers (CFM) than in soil amended with CF alone, and the highest in topsoil (0–20 cm).  The nosZ-denitrifier community composition was more complex in CFM soil than in CF soil.  Specific species were detected only in the CFM soil.  The abundance of nosZ-denitrifier in the NPKM treatment was approximately two times higher than that in the CK, N, and NPK treatments.  Most of the cloned nosZ sequences were closely related to nosZ sequences from Bradyrhizobiaceae and Rhodospirillaceae in Alphaproteobacteria.  Of the measured abiotic factors, soil organic matter correlated significantly with the abundance (P<0.01); available phosphorus correlated significantly with the topsoil community composition (P<0.01), whereas soil organic matter correlated significantly with the subsoil (20–90 cm) community composition (P<0.01). This study demonstrated that long-term CFM fertilization affected both the abundance and composition of the nosZ-denitrifier community.