Roots of most terrestrial plants form symbiotic associations (mycorrhiza) with soil- borne arbuscular mycorrhizal fungi (AMF). Many studies show that mycorrhizal colonization enhances plant resistance against pathogenic fungi. However, the mechanism of mycorrhiza-induced disease resistance remains equivocal. In this study, we found that mycorrhizal inoculation with AMF Funneliformis mosseae significantly alleviated tomato (Solanum lycopersicum Mill.) early blight disease caused by Alternaria solani Sorauer. AMF pre-inoculation led to significant increases in activities of β-1,3-glucanase, chitinase, phenylalanine ammonia-lyase (PAL) and lipoxygenase (LOX) in tomato leaves upon pathogen inoculation. Mycorrhizal inoculation alone did not influence the transcripts of most genes tested. However, pathogen attack on AMF-inoculated plants provoked strong defense responses of three genes encoding pathogenesis-related proteins, PR1, PR2, and PR3, as well as defense-related genes LOX, AOC, and PAL, in tomato leaves. The induction of defense responses in AMF pre-inoculated plants was much higher and more rapid than that in un-inoculated plants in present of pathogen infection. Three tomato genotypes: a Castlemart wild-type (WT) plant, a jasmonate (JA) biosynthesis mutant (spr2), and a prosystemin-overexpressing 35S::PS plant were used to examine the role of the JA signaling pathway in AMF-primed disease defense. Pathogen infection on mycorrhizal 35S::PS plants led to higher induction of defense-related genes and enzymes relative to WT plants. However, pathogen infection did not induce these genes and enzymes in mycorrhizal spr2 mutant plants. Bioassays showed that 35S::PS plants were more resistant and spr2 plants were more susceptible to early blight compared with WT plants. Our finding indicates that mycorrhizal colonization enhances tomato resistance to early blight by priming systemic defense response, and the JA signaling pathway is essential for mycorrhiza-primed disease resistance.
As an r-strategy insect species, the brown planthopper (BPH) Nilaparvata lugens (Stål) is a serious pest of rice crops in the temperate and tropical regions of Asia and Australia, which may be due to its robust fecundity. Here we combined 2-DE comparative proteomic and RNA-seq transcriptomic analyses to identify fecundity-related proteins and genes. Using high- and low-fecundity populations as sample groups, a total of 54 and 75 proteins were significantly altered in the third and sixth day brachypterous female stages, respectively, and 39 and 54 of these proteins were identified by MALDI-TOF/TOF MS. In addition, 71,966 unigenes were quantified by Illumina sequencing. On the basis of the transcriptomic analysis, 7408 and 1639 unigenes demonstrated higher expression levels in the high-fecundity population in the second day brachypterous female adults and the second day fifth instar nymphs, respectively, and 411 unigenes were up-regulated in both groups. Of these dozens of proteins and thousands of unigenes, five were differentially expressed at both the protein and mRNA levels at all four time points, suggesting that these genes may regulate fecundity. Glutamine synthetase (GS) was chosen for further functional studies. RNAi knockdown of the GS gene reduced the fecundity of N. lugens by 64.6%, disrupted ovary development, and inhibited vitellogenin (Vg) expression. Our results show that a combination of proteomic and transcriptomic analyses provided five candidate proteins and genes for further study. The knowledge gained from this study may lead to a more fundamental understanding of the fecundity of this important agricultural insect pest.
Aminoglycoside antibiotics target an internal RNA loop within the bacterial ribosomal decoding site. Here, we described the synthesis and SAR of novel 3,5-diamino-piperidine derivatives as aminoglycoside mimetics, and show they act as inhibitors of bacterial translation and growth. KeywordsAminoglycosides; Antibiotics; Translation inhibitors; 2-deoxy-streptamine; Ribosome; Decoding site; 3; 5-diamino-piperidine Bacterial resistance to antibiotics is on the rise and represents a global medical threat. In hospitals in the United States, approximately two million patients per year are infected. 1 The majority of these nosocomial pathogens are resistant to at least one antibiotic and result in about 90,000 deaths per year; a number that has increased 7-fold over the last decade. The recent and rapid spread of community acquired methicillin resistant Staphylococcus aureus further highlights the threat of resistance development and illustrates the need for new antibiotics that work by novel mechanisms. 2 Given the broad genetic and physiological diversity of bacterial pathogens and the need for empiric therapies that cover a broad panel of organisms, it is not surprising that discovery of new antibiotics has advanced slowly. Central to antibiotic discovery is identifying broadly validated targets. One such proven target is the bacterial ribosome, which is the target for a significant number of clinically important antibiotics that bind at the ribosomal RNA (rRNA). 3 Here, we expand on the description of a novel series of antibacterial compounds that target rRNA and blocks bacterial translation and growth. 4Three-dimensional structures of different aminoglycosides bound to the decoding site, or Asite, within the 16S rRNA have been determined by X-ray crystallography. 5 Importantly, these studies have shown that 2-deoxystreptamine (2-DOS), a conserved core scaffold among aminoglycosides, binds in a similar manner regardless of the 4,5-or 4,6-disubstitutions found in the neomycin or gentamicin families, respectively (Fig. 1) Publisher's Disclaimer: This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final citable form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. NIH Public Access NIH-PA Author ManuscriptNIH-PA Author Manuscript NIH-PA Author Manuscript groups of 2-DOS are predominantly involved in base recognition by forming conserved hydrogen bonds with A1493, G1494 and U1495 of the 16S rRNA. These interactions anchor the aminoglycoside scaffold within the A-site internal loop and displace residues A1492 and A1493 from the RNA interior. These two adenine residues act as a molecular switch that is involved in securing the fidelity of translation by interacting w...
The target of rapamycin (TOR) positively controls cell growth in response to nutrients such as amino acids. However, research on the specific nutrients sensed by TOR is limited. Glutamine (Gln), a particularly important amino acid involved in metabolism in organisms, is synthesised and catalysed exclusively by glutamine synthetase (GS), and our previous studies have shown that Gln may regulate fecundity in vivo levels of the brown planthopper (BPH) Nilaparvata lugens. Until now, it has remained unclear whether Gln activates or inhibits the TOR signalling pathway. Here, we performed the combined analyses of iTRAQ (isobaric tags for relative and absolute quantification) and DGE (tag-based digital gene expression) data in N.lugens at the protein and transcript levels after GS RNAi, and we found that 52 pathways overlap, including the TOR pathway. We further experimentally demonstrate that Gln activates the TOR pathway by promoting the serine/threonine protein kinase AKT and inhibiting the 5′AMP-activated protein kinase AMPK phosphorylation activity in the pest. Furthermore, TOR regulates the fecundity of N. lugens probably by mediating vitellogenin (Vg) expression. This work is the first report that Gln activates the TOR pathway in vivo.
We report the structure-guided discovery, synthesis, and initial characterization of 3,5-diamino-piperidinyl triazines (DAPT), a novel translation inhibitor class that targets bacterial rRNA and exhibits broad-spectrum antibacterial activity. DAPT compounds were designed as structural mimetics of aminoglycoside antibiotics which bind to the bacterial ribosomal decoding site and thereby interfere with translational fidelity. We found that DAPT compounds bind to oligonucleotide models of decoding-site RNA, inhibit translation in vitro, and induce translation misincorporation in vivo, in agreement with a mechanism of action at the ribosomal decoding site. The novel DAPT antibacterials inhibit growth of gram-positive and gram-negative bacteria, including the respiratory pathogen Pseudomonas aeruginosa, and display low toxicity to human cell lines. In a mouse protection model, an advanced DAPT compound demonstrated efficacy against an Escherichia coli infection at a 50% protective dose of 2.4 mg/kg of body weight by single-dose intravenous administration.
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