Agrobacterium tumefaciens causes crown gall disease by transferring and integrating bacterial DNA (T-DNA) into the plant genome. To examine the physiological changes and adaptations during Agrobacterium-induced tumor development, we compared the profiles of salicylic acid (SA), ethylene (ET), jasmonic acid (JA), and auxin (indole-3-acetic acid [IAA]) with changes in the Arabidopsis thaliana transcriptome. Our data indicate that host responses were much stronger toward the oncogenic strain C58 than to the disarmed strain GV3101 and that auxin acts as a key modulator of the ArabidopsisAgrobacterium interaction. At initiation of infection, elevated levels of IAA and ET were associated with the induction of host genes involved in IAA, but not ET signaling. After T-DNA integration, SA as well as IAA and ET accumulated, but JA did not. This did not correlate with SA-controlled pathogenesis-related gene expression in the host, although high SA levels in mutant plants prevented tumor development, while low levels promoted it. Our data are consistent with a scenario in which ET and later on SA control virulence of agrobacteria, whereas ET and auxin stimulate neovascularization during tumor formation. We suggest that crosstalk among IAA, ET, and SA balances pathogen defense launched by the host and tumor growth initiated by agrobacteria.

BACKGROUND & AIMS: Q6Although coronavirus disease 2019 (COVID-19) is characterized by fever and respiratory symptoms, some patients have no or mild symptoms. Severe acute respiratory syndromecoronavirus (SARS-CoV-2) has been detected in feces of patients. We investigated gastrointestinal symptoms and shedding of virus into feces of patients with asymptomatic or mild COVID-19. METHODS:We collected data from 46 patients (median age, 26 y; 46% men) with asymptomatic or mild COVID-19 (without fever and pneumonia) and prolonged respiratory shedding of SARS-CoV-2, quarantined from April 4, 2020, through April 24, 2020, in Korea. Respiratory specimens included upper respiratory specimens (nasopharyngeal and oropharyngeal swabs) and lower respiratory specimens (sputum), and were collected twice per week. The median interval between COVID-19 diagnosis to the start of fecal sample collection was 37 days (range, 29-41 d); 213 stool specimens were collected from 46 patients. We used real-time reverse-transcription polymerase chain reaction to detect SARS-CoV-2 in the respiratory and fecal specimens. RESULTS:Gastrointestinal manifestations were observed in 16 of the 46 patients (35%); diarrhea was the most common (15%), followed by abdominal pain (11%), dyspepsia (11%), and nausea (2%).Virus RNA was detected in feces from 2 patients without gastrointestinal symptoms (4%). Mean cycle threshold values from the time of quarantine to the time of fecal collection tended to be lower in patients with virus detected in fecal samples than in patients without virus in fecal samples (29.91 vs 33.67 in the first week, 29.47 vs 35.71 in the fifth week, respectively). Shedding of virus into feces persisted until day 50 after diagnosis; fecal samples began to test negative before or at approximately the time that respiratory specimens also began to test negative. CONCLUSIONS:In an analysis of fecal and respiratory specimens from patients with COVID-19 in quarantine in Korea, we found that the gastrointestinal tract could be a route of transmission of SARS-CoV-2 even in patients with asymptomatic or mild disease, with no gastrointestinal symptoms. The viral load of the respiratory specimens appears be related to shedding of the virus into feces in this group of patients.

Crown gall tumors induced by Agrobacterium tumefaciens represent a sink that has to be provided with nutrients and water by the host plant. The lack of an intact epidermis or cuticle results in uncontrolled loss of water. However, neither the tumor nor the host plant displays wilting. This phenomenon points to drought adaptation in both tumors and the crown gall host plant. To understand the underlying molecular mechanisms of protection against desiccation the gene expression pattern of Arabidopsis (Arabidopsis thaliana) tumors was integrated with the profile of stress metabolites: Arabidopsis tumors accumulated high amounts of abscisic acid (ABA), the ethylene precursor aminocyclopropyl carboxylic acid, osmoprotectants, and form a suberized periderm-like protective layer. Suberization of the outer tumor cell layers most likely is mediated by ABA since external application of ABA induced suberization of Arabidopsis roots. However, the expression level of the classical marker genes, known to respond to drought stress and/or ABA, was lower in tumors. Instead another set of drought and/or ABAinducible genes was more highly transcribed. Elevated transcription of several ABA-dependent aquaporin genes might indicate that ABA controls the water balance of the tumor. The retarded tumor growth on abi and aba mutant plants underlined the importance of a tumor-specific ABA signaling pathway. Taken together, we propose that ABA is an important signal for protection of tumors against desiccation and thus supports tumor development.

Targeted proteomics has become increasingly popular recently because of its ability to precisely quantify selected proteins in complex cellular backgrounds. Here, we demonstrated the utility of an LTQ-Orbitrap Velos Pro mass spectrometer in targeted parallel reaction monitoring (PRM) despite its unconventional dual ion trap configuration. We evaluated absolute specificity (>99%) and sensitivity (100 amol on column in 1 μg of total cellular extract) using full and mass range scans as survey scans together with data-dependent (DDA) and targeted MS/MS acquisition. The instrument duty cycle was a critical parameter limiting sensitivity, necessitating peptide retention time scheduling. We assessed synthetic peptide and recombinant peptide standards to predict or experimentally determine target peptide retention times. We applied optimized PRM to protein degradation in signaling regulation, an area that is receiving increased attention in plant physiology. We quantified relative abundance of selected proteins in plants that are mutant for enzymatic components of the N-end rule degradation (NERD) pathway such as the two tRNA-arginyl-transferases ATE1 and ATE2 and the two E3 ubiquitin ligases PROTEOLYSIS1 and 6. We found a number of upregulated proteins, which might represent degradation targets. We also targeted FLAGELLIN SENSITIVE2 (FLS2), a pattern recognition receptor responsible for pathogen sensing, in ubiquitin ligase mutants to assay the attenuation of plant immunity by degradation of the receptor.

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