We identified a glycoside hydrolase family 12 (GH12) protein, XEG1, produced by the soybean pathogen Phytophthora sojae that exhibits xyloglucanase and b-glucanase activity. It acts as an important virulence factor during P. sojae infection but also acts as a pathogen-associated molecular pattern (PAMP) in soybean (Glycine max) and solanaceous species, where it can trigger defense responses including cell death. GH12 proteins occur widely across microbial taxa, and many of these GH12 proteins induce cell death in Nicotiana benthamiana. The PAMP activity of XEG1 is independent of its xyloglucanase activity. XEG1 can induce plant defense responses in a BAK1-dependent manner. The perception of XEG1 occurs independently of the perception of ethylene-inducing xylanase. XEG1 is strongly induced in P. sojae within 30 min of infection of soybean and then slowly declines. Both silencing and overexpression of XEG1 in P. sojae severely reduced virulence. Many P. sojae RXLR effectors could suppress defense responses induced by XEG1, including several that are expressed within 30 min of infection. Therefore, our data suggest that PsXEG1 contributes to P. sojae virulence, but soybean recognizes PsXEG1 to induce immune responses, which in turn can be suppressed by RXLR effectors. XEG1 thus represents an apoplastic effector that is recognized via the plant's PAMP recognition machinery.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) can cause acute respiratory disease and multiorgan failure. Finding human host factors that are essential for SARS-CoV-2 infection could facilitate the formulation of treatment strategies. Using a human kidney cell line—HK-2—that is highly susceptible to SARS-CoV-2, we performed a genome-wide RNAi screen and identified virus dependency factors (VDFs), which play regulatory roles in biological pathways linked to clinical manifestations of SARS-CoV-2 infection. We found a role for a secretory form of SARS-CoV-2 receptor, soluble angiotensin converting enzyme 2 (sACE2), in SARS-CoV-2 infection. Further investigation revealed that SARS-CoV-2 exploits receptor-mediated endocytosis through interaction between its spike with sACE2 or sACE2-vasopressin via AT1 or AVPR1B, respectively. Our identification of VDFs and the regulatory effect of sACE2 on SARS-CoV-2 infection shed insight into pathogenesis and cell entry mechanism of SARS-CoV-2 as well as potential treatment strategies for COVID-19.

The extracellular space (apoplast) of plant tissue represents a critical battleground between plants and attacking microbes. Here we show that a pathogen-secreted apoplastic xyloglucan-specific endoglucanase, PsXEG1, is a focus of this struggle in the -soybean interaction. We show that soybean produces an apoplastic glucanase inhibitor protein, GmGIP1, that binds to PsXEG1 to block its contribution to virulence., however, secretes a paralogous PsXEG1-like protein, PsXLP1, that has lost enzyme activity but binds to GmGIP1 more tightly than does PsXEG1, thus freeing PsXEG1 to support infection. The gene pair encoding PsXEG1 and PsXLP1 is conserved in many species, and the orthologs PpXEG1 and PpXLP1 have similar functions. Thus, this apoplastic decoy strategy may be widely used in pathosystems.

Denitrification is an important process in the global nitrogen cycle. The genes encoding NirK and NirS (nirK and nirS), which catalyze the reduction of nitrite to nitric oxide, have been used as marker genes to study the ecological behavior of denitrifiers in environments. However, conventional polymerase chain reaction (PCR) primers can only detect a limited range of the phylogenetically diverse nirK and nirS. Thus, we developed new PCR primers covering the diverse nirK and nirS. Clone library and qPCR analysis using the primers showed that nirK and nirS in terrestrial environments are more phylogenetically diverse and 2-6 times more abundant than those revealed with the conventional primers. RNA-and culture-based analyses using a cropland soil also suggested that microorganisms with previously unconsidered nirK or nirS are responsible for denitrification in the soil. PCR techniques still have a greater capacity for the deep analysis of target genes than PCR-independent methods including metagenome analysis, although efforts are needed to minimize the PCR biases. The methodology and the insights obtained here should allow us to achieve a more precise understanding of the ecological behavior of denitrifiers and facilitate more precise estimate of denitrification in environments.

Ethylene regulates a variety of stress responses and developmental adaptation in plants. In the present study, the phosphoproteomics is adopted to investigate the differential protein phosphorylation by ethylene in Arabidopsis ethylene-insensitive 2 (ein2) mutant. A total of 224 phosphopeptides were identified, of which 64 phosphopeptides were detected three or more times. Ethylene induces a general reduction in phosphorylated proteins in ein2. Totally, three ethylene-enhanced and three ethylene-repressible unique phosphopeptides were identified, respectively. Classification of the cellular functions of these phosphoproteins revealed that 55.5% of them are related to signaling and gene expression. Peptide sequence alignment reveals two highly conserved phosphorylation motifs, PRVD/GSx and SPDYxx. Alignment of these phosphopeptides with Arabidopsis proteins reveals five phosphorylation motifs. Both ethylene-enhanced and -repressible phosphopeptides present in these motifs. EIL-1, ERF110 transcription factors and Hua enhancer 4 (HEN4) are predicted to contain one of the phosphorylation motifs. The phosphorylation of the motif-containing peptides has been validated by the in vitro kinase assays coupled with MS analysis. The differential regulation of phosphorylation by ethylene is substantiated by Western dot blot analysis. Taken together, these results suggest that ethylene signals may be transduced by a phosphor-relay from receptors to transcriptional events via both ein2-dependent and -independent pathways.