Small Ribosomal Subunit Research Articles

KsgA facilitates ribosomal small subunit maturation by proofreading a key structural lesion.

Ribosome assembly is orchestrated by many assembly factors, including ribosomal RNA methyltransferases, whose precise role is poorly understood. Here, we leverage the power of cryo-EM and machine learning to discover that the E. coli methyltransferase KsgA performs a 'proofreading' function in the assembly of the small ribosomal subunit by recognizing and partially disassembling particles that have matured but are not competent for translation. We propose that this activity allows inactive particles an opportunity to reassemble into an active state, thereby increasing overall assembly fidelity. Detailed structural quantifications in our datasets additionally enabled the expansion of the Nomura assembly map to highlight rRNA helix and r-protein interdependencies, detailing how the binding and docking of these elements are tightly coupled. These results have wide-ranging implications for our understanding of the quality-control mechanisms governing ribosome biogenesis and showcase the power of heterogeneity analysis in cryo-EM to unveil functionally relevant information in biological systems.

Experimental upregulation of developmentally downregulated ribosomal protein large subunits 7 and 7A promotes axon regeneration after injury in vivo

Ribosomal proteins are involved in neurodevelopment and central nervous system (CNS) disease and injury. However, the roles of specific ribosomal protein subunits in developmental axon growth, and their potential as therapeutic targets for treating CNS injuries, are still poorly understood. Here, we show that ribosomal protein large (Rpl) and small (Rps) subunit genes are substantially (56-fold) enriched amongst the genes, which are downregulated during maturation of retinal ganglion cell (RGC) CNS projection neurons. We also show that Rpl and Rps subunits are highly co-regulated in RGCs, and partially re-upregulated after optic nerve crush (ONC). Because developmental downregulation of ribosomal proteins coincides with developmental decline in neuronal intrinsic axon growth capacity, we hypothesized that Rpl/Rps incomplete re-upregulation after injury may be a part of the cellular response which attempts to reactivate intrinsic axon growth mechanisms. We found that experimentally upregulating Rpl7 and Rpl7A promoted axon regeneration after ONC in vivo. Finally, we characterized gene networks associated with Rpl/Rps, and showed that Rpl7 and Rpl7A belong to the cluster of genes, which are shared between translational and neurodevelopmental biological processes (based on gene-ontology) that are co-downregulated in maturing RGCs during the decline in intrinsic axon growth capacity.

Molecular Identification of Planococcus citri (Hemiptera: Pseudococcidae)

Planococcus citri is an important phytophagous pest in different agroecosystems. The species is very difficult to distinguish by morphological features. The goal of this research was to present basic data on the molecular data to confirm P. citri. The primers used in the molecular identification of P. citri consisted of mitochondrial cytochrome c oxidase subunit 1 (COI), ribosomal small subunit RNA (18S rDNA) gene, and internal transcribed spacer 2 (ITS2) gene. The 1% (w/v) agarose gel showed the presence of successful amplification of the COI, 18S rDNA, and ITS2 genes indicated with positive PCR products. The Internal transcribed spacer (ITS2), 18S ribosomal and Cytochrome c oxidase I (COI) mitochondrial genes used in this study confirmed the identity of mealybugs as P. citri. The 18S ribosomal gene showed 98% nucleotide sequence homology to the P. citri USA isolate while the COI gene and ITS2 gene showed less than 95% nucleotide sequence homology to the P. citri USA isolate and P. citri Israel isolate, respectively. At present, the nucleotide sequence data of mealybugs is still lacking; consequently, mealybug species must be correctly identified for the proper management of this pest.

On translational control by ribosome speed in S. cerevisiae

Introduction: In addition to the widespread and well documented control of protein synthesis by translation initiation, recent evidence suggests that translation elongation can also control protein synthesis rates. One of the proposed mechanisms leading to elongation control is the interference of slow ribosome movement around the start codon with efficient translation initiation. Here we estimate the frequency with which this mode of control occurs in baker’s yeast growing in rich medium.Methods: We interrogate published genome-wide datasets for evidence of transcripts associated with queueing small ribosomal subunits, and confirm results from these surveys using additional experimental work.Results: Our analyses reveal that transcripts from around 20% of yeast genes show evidence of queueing ribosomes, which may be indicative of translation elongation control. Moreover, this subset of transcripts is sensitive to distinct regulatory signals compared to initiation-controlled mRNAs, and such distinct regulation occurs, for example, during the response to osmotic stress.Discussion: Our analyses provide a first quantitative estimate for the prevalence of translational control exerted via the elongation stage in a commonly used model organism, and suggest that transcript under elongation control form a separately addressable RNA regulon.

First Report of Macrophomina phaseolina Causing Leaf Blight of Cassava in China.

Cassava (Manihot esculenta Crantz) is an important tropical and subtropical crop that feeds nearly 600 million people worldwide and is widely grown in Hainan Province, China (Vanderschuren et al., 2014). In November 2021, leaf blight symptoms were observed on South China 6 (SC6) cassava plants in Haikou City, Hainan Province, China. The disease was presented in almost every cassava plant we observed. The rotten leaves were shown to be infected but not the root or stem. The lesions started on the plant's lower leaves and gradually developed on the upper leaves of the entire cassava plant. The infected leaves gradually withered. Microscopic observation showed that the infected leaves exhibited necrotic lesions with pycnidial structures all over their surface. Diseased leaf segments (4 × 4 mm) were disinfected for 30 seconds with sodium hypochlorite 1% solution and then rinsed with sterile water for 30 seconds before being placed on potato dextrose agar (PDA) medium. Plates were incubated at 28°C in complete darkness. Marginal hyphae were picked and placed on a new PDA medium, and pure cultures were obtained after multiple transfers. The hyphae started white and gradually changed to a fluffy black-gray color as it grew on the PDA. Microscopic observation showed that there were a large number of ellipsoidal microsclerotia between the hyphae. Microsclerotia were sub fusiform, and hyaline, with a length of about 40 μm. The ribosomal internal transcribed spacer (ITS) region, ribosomal small subunit (SSU) region, and ribosomal large subunit (LSU) region of the isolate were amplified and sequenced using primers ITS1 and ITS4, NS1 and NS4 (White et al., 1990), and LROR and LR5 (Moriya et al., 2005), respectively. The obtained ITS (GenBank accession no. OP185242), SSU (GenBank accession no. OQ165195), and LSU (GenBank accession no. OQ118350.1) had 99.8% (100% coverage), 100% (100% coverage), and 100% (100% coverage) identities with the references ITS (GenBank accession no. KF951698), SSU (GenBank accession no. KF766281.1), and LSU (GenBank accession no. KF766364.1) in Macrophomina phaseolina, respectively. A phylogenetic tree was constructed with software MEGA7 using the maximum likelihood method, showing that the isolate was grouped in the same clade as M. phaseolina. To prove Koch's postulates, five healthy SC6 cassava plants (2-month-old) with 4-6 leaves were wounded with a small pin and inoculated with PDA blocks (3 × 3 mm) excised from the margin of a 7-day-cultured colony (Hu et al., 2022). Healthy plants treated with sterile PDA plugs served as controls. All plants were grown at 25°C with a 12-h light/dark rotation. After 7 days, typical blight symptoms developed on leaves inoculated with M. phaseolina, but not on the controls. The fungus was isolated from infected leaves. Based on molecular identification, M. phaseolina was re-isolated from leaves with leaf blight symptoms. Macrophomina is typically found to cause root and lower stem rot on cassava in Africa (Msikita et al., 1998). To the best of our knowledge, this is the first report of M. phaseolina causing leaf blight on cassava in China. Our finding provides a foundation to management of this disease.

The induction of p53 correlates with defects in the production, but not the levels, of the small ribosomal subunit and stalled large ribosomal subunit biogenesis.

Ribosome biogenesis is one of the biggest consumers of cellular energy. More than 20 genetic diseases (ribosomopathies) and multiple cancers arise from defects in the production of the 40S (SSU) and 60S (LSU) ribosomal subunits. Defects in the production of either the SSU or LSU result in p53 induction through the accumulation of the 5S RNP, an LSU assembly intermediate. While the mechanism is understood for the LSU, it is still unclear how SSU production defects induce p53 through the 5S RNP since the production of the two subunits is believed to be uncoupled. Here, we examined the response to SSU production defects to understand how this leads to the activation of p53 via the 5S RNP. We found that p53 activation occurs rapidly after SSU production is blocked, prior to changes in mature ribosomal RNA (rRNA) levels but correlated with early, middle and late SSU pre-rRNA processing defects. Furthermore, both nucleolar/nuclear LSU maturation, in particular late stages in 5.8S rRNA processing, and pre-LSU export were affected by SSU production defects. We have therefore uncovered a novel connection between the SSU and LSU production pathways in human cells, which explains how p53 is induced in response to SSU production defects.

Differential Participation of Plant Ribosomal Proteins from the Small Ribosomal Subunit in Protein Translation under Stress.

Upon exposure to biotic and abiotic stress, plants have developed strategies to adapt to the challenges imposed by these unfavorable conditions. The energetically demanding translation process is one of the main elements regulated to reduce energy consumption and to selectively synthesize proteins involved in the establishment of an adequate response. Emerging data have shown that ribosomes remodel to adapt to stresses. In Arabidopsis thaliana, ribosomes consist of approximately eighty-one distinct ribosomal proteins (RPs), each of which is encoded by two to seven genes. Recent research has revealed that a mutation in a given single RP in plants can not only affect the functions of the RP itself but can also influence the properties of the ribosome, which could bring about changes in the translation to varying degrees. However, a pending question is whether some RPs enable ribosomes to preferentially translate specific mRNAs. To reveal the role of ribosomal proteins from the small subunit (RPS) in a specific translation, we developed a novel approach to visualize the effect of RPS silencing on the translation of a reporter mRNA (GFP) combined to the 5'UTR of different housekeeping and defense genes. The silencing of genes encoding for NbRPSaA, NbRPS5A, and NbRPS24A in Nicotiana benthamiana decreased the translation of defense genes. The NbRACK1A-silenced plant showed compromised translations of specific antioxidant enzymes. However, the translations of all tested genes were affected in NbRPS27D-silenced plants. These findings suggest that some RPS may be potentially involved in the control of protein translation.

First identification and molecular subtyping of Blastocystis in free-living wild birds from urban Xinxiang, China.

Blastocystis is a common enteric protist infecting humans, domestic animals, and wildlife worldwide. However, data on the prevalence and subtype diversity of Blastocystis in free-living wild birds in urban districts are rare. In this study, a total of 138 fresh fecal samples from free-living wild birds were collected from three universities and three communities in Xinxiang, China, to explore the infection rate, Blastocystis subtypes present and zoonotic potential of this protist. Blastocystis presence was determined with nested-PCR amplification based on the partial small ribosomal subunit (SSU rRNA) gene. Presence was detected from one community (Wupu) at an overall rate of 1.5% (2/136). Further DNA sequencing and phylogenetic analyses identified two ruminant-associated subtypes, ST10 (n = 1) and ST24 (n = 1), implying a cross-species transmission of Blastocystis from ruminants. This is the first report on the infection of ST10 and ST24 in free-living wild birds in an urban area in China. As potentially zoonotic subtypes, the occurrence of ST10 and ST24 suggests that these free-living birds could play a role in spreading Blastocystis to humans in Xinxiang.

Ribosomal Dysfunction Is a Common Pathomechanism in Different Forms of Trichothiodystrophy.

Mutations in a broad variety of genes can provoke the severe childhood disorder trichothiodystrophy (TTD) that is classified as a DNA repair disease or a transcription syndrome of RNA polymerase II. In an attempt to identify the common underlying pathomechanism of TTD we performed a knockout/knockdown of the two unrelated TTD factors TTDN1 and RNF113A and investigated the consequences on ribosomal biogenesis and performance. Interestingly, interference with these TTD factors created a nearly uniform impact on RNA polymerase I transcription with downregulation of UBF, disturbed rRNA processing and reduction of the backbone of the small ribosomal subunit rRNA 18S. This was accompanied by a reduced quality of decoding in protein translation and the accumulation of misfolded and carbonylated proteins, indicating a loss of protein homeostasis (proteostasis). As the loss of proteostasis by the ribosome has been identified in the other forms of TTD, here we postulate that ribosomal dysfunction is a common underlying pathomechanism of TTD.

Human nucleolar protein SURF6/RRP14 participates in early steps of pre-rRNA processing.

The biogenesis of ribosomes requires tightly controlled transcription and processing of pre-rRNA which comprises ribosomal RNAs forming the core of large and small ribosomal subunits. Early steps of the pre-rRNA processing and assembly of the ribosomal subunits require a large set of proteins that perform folding and nucleolytic cleavage of pre-rRNAs in the nucleoli. Structure and functions of proteins involved in the pre-rRNA processing have been extensively studied in the budding yeast S. cerevisiae. Functional characterization of their human homologues is complicated by the complexity of mammalian ribosomes and increased number of protein factors involved in the ribosomal biogenesis. Homologues of human nucleolar protein SURF6 from yeast and mouse, Rrp14 and Surf6, respectively, had been shown to be involved in the early steps of pre-rRNA processing. Rrp14 works as RNA chaperone in complex with proteins Ssf1 and Rrp15. Human SURF6 knockdown and overexpression were used to clarify a role of SURF6 in the early steps of pre-rRNA processing in human cell lines HeLa and HTC116. By analyzing the abundance of the rRNA precursors in cells with decreased level or overexpression of SURF6, we demonstrated that human SURF6 is involved in the maturation of rRNAs from both small and large ribosomal subunits. Changes in the SURF6 level caused by knockdown or overexpression of the protein do not result in the death of HeLa cells in contrast to murine embryonic fibroblasts, but significantly alter the distribution of cells among the phases of the cell cycle. SURF6 knockdown in both p53 sufficient and p53 deficient HCT116 human cancer cells results in elongation of G0/G1 and shortening of G2/M phase. This surprising result suggests p53 independence of SURF6 effects on the cell cycle and possible multiple functions of SURF6. Our data point to the shift from pathway 1 to pathway 2 of the rRNA biogenesis caused by the SURF6 knockdown and its likely association with p53 pathway.

Myxozoan Ceratomyxids Infecting the Gallbladder of Amazonian Ornamental Cichlid Fish: Description of Ellipsomyxa santarenensis n. sp. and Report of Ceratomyxa amazonensis in a New Host

Although most Myxozoa species of the genera Ceratomyxa and Ellipsomyxa have been described in marine hosts worldwide, an increasing diversity has been reported infecting South American freshwater fish, mainly in Amazonian waters. The present study deals with two species of myxozoan ceratomyxids parasitizing the gallbladder of Amazonian ornamental cichlids fish: Ceratomyxa amazonensis is identified from a new host—Geophagus altifrons; while Ellipsomyxa santarenensis n. sp. is described infecting Satanoperca jurupari. Morphological (light microscopy and transmission electron microscopy), molecular (small ribosomal subunit DNA—SSU-rDNA sequencing) and phylogenetic analyses were used to characterize both species. Ceratomyxa amazonensis showed a prevalence of 64.2%, with plasmodia showing a vermiform shape and motility. For E. santarenensis n. sp., the prevalence was 33.3%. Ultrastructural analysis revealed that the vermiform C. amazonensis plasmodia were composed of an outer cytoplasmic region and a large vacuole occupying the inner area. In E. santarenensis n. sp., cytoplasmic expansions were observed in pseudoplasmodia originating pseudopodia. SSU rDNA sequencing-based genetic distance analysis revealed a very small difference between C. amazonensis, parasite of G. altifrons, and C. amazonensis, parasite of S. discus—host of the original description, thus showing that they are the same species occurring in a new host. For Ellipsomyxa santarenensis n. sp., molecular data revealed a difference of 1.6% for Ellipsomyxa amazonensis and Ellipsomyxa paraensis. The phylogenetic analysis revealed the grouping of E. santarenensis n. sp. together with the other freshwater Ellipsomyxa species of the Amazonian region, and associated with the morphological data, it was possible to identify it as a new taxon within the genus Ellipsomyxa.

Backbone resonance assignments of the C-terminal region of human translation initiation factor eIF4B.

Translation initiation in eukaryotes is an early step in protein synthesis, requiring multiple factors to recruit the ribosomal small subunit to the mRNA 5' untranslated region. One such protein factor is the eukaryotic translation initiation factor 4B (eIF4B), which increases the activity of the eIF4A RNA helicase, and is linked to cell survival and proliferation. We report here the protein backbone chemical shift assignments corresponding to the C-terminal 279 residues of human eIF4B. Analysis of the chemical shift values identifies one main helical region in the area previously linked to RNA binding, and confirms that the overall C-terminal region is intrinsically disordered.

Multiple environmental factors, but not nutrient addition, directly affect wet grassland soil microbial community structure: a mesocosm study.

Nutrient addition may change soil microbial community structure, but soil microbes must simultaneously contend with other, interacting factors. We studied the effect of soil type (peat, mineral), water level (low, high) and nutrient addition (unfertilized, fertilized) on wet grassland soil microbial community structure in both vegetated and un-vegetated soils after five years of treatment application in a mesocosm, using Illumina sequencing of the bacterial V4 region of the small ribosomal sub-units. Soil type, water level and plant presence significantly affected the soil microbial structure both singly and interactively. Nutrient addition did not directly impact microbiome structure, but acted indirectly by increasing plant biomass. The abundance of possible plant growth promoting bacteria and heterotrophic bacteria indicate the importance of bacteria that promote plant growth. Based on our results, a drier and warmer future would result in nutrient-richer conditions, and changes to microbial community structure and total microbial biomass and /or abundances, with wet grasslands likely switching from areas acting as C sinks to C sources.

Assessment of the macroalgal diversity of Kuwait by using the Germling Emergence Method

Cryptic stages of diverse macroalgae present in natural substrata, “the bank of microscopic forms”, were isolated into clonal cultures and identified based on both morphological characteristics and DNA barcoding. Approximately 120 clonal isolates from 308 natural substratum samples were collected from the entire coastline of Kuwait. Amongst these isolates, 77 (64%) were identified through DNA barcoding using the nuclear ribosomal small subunit, RuBisCO spacer (ITS2, <i>tufa</i>, <i>rbc</i>L, <i>psa</i>A, and <i>psb</i>A) and sequencing. Twenty-six isolates (34%) were identified in the division Chlorophyta, 18 (23%) as Phaeophyceae, and 33 (43%) as Rhodophyta. For all DNA sequences in this study, species-level cut off applied was ≥98% homology which depend entirely on the markers used. Three putative new records of Chlorophyta new for the Arabian Gulf were made: <i>Cladophora laetevirens</i> (Dillwyn) Kützing, <i>Ulva torta</i> (Mertens) Trevisan and <i>Ulvella leptochaete</i> (Huber) R. Nielsen, C. J. O′Kelly & B. Wysor in Nielsen, while <i>Cladophora gracilis</i> Kützing and <i>Ulva ohnoi</i> M. Hiraoka & <i>S. Shimada</i> are new records for Kuwait. For Phaeophyceae, Ectocarpus subulatus Kützing and <i>Elachista stellaris</i> Areschoug were new records for the Gulf and Kuwait. In the Rhodophyta, <i>Acrochaetium secundatum</i> (Lyngbye) Nägeli in Nägeli & Cramer, <i>Ceramium affine</i> Setchell & N. L. Gardner, <i>Gelidium pusillum</i> var. <i>pakistanicum</i> Afaq-Husain & Shameel and <i>Dasya caraibica</i> Børgesen are new records for the Gulf and Kuwait, while the red alga <i>Stylonema alsidii</i> (Zanardini) K. Drew is a new record for Kuwait. Several isolates identified corresponded to genera not previously reported in Kuwait and / or the Arabian Gulf, such as <i>Porphyrostromium</i> Trevisan, a new genus from the Bangiales, and two unidentified species for the Planophilaceae Škaloud & Leliaert. The isolates cultivated from substrata enhance understanding of the marine macroalgal diversity in the region and confirmed that the Germling Emergence Method is suitable for determining the actual diversity of a given study area through isolation from cryptic life-history phases.

BOTH THE INFECTION STATUS AND INFLAMMATORY MICROENVIRONMENT INDUCE TRANSCRIPTIONAL REMODELING IN MACROPHAGES IN MURINE LEISHMANIAL LESIONS.

Cutaneous leishmaniasis is caused by infection with the protozoan parasite Leishmania, which resides intracellularly in dermal macrophages (Mø), producing lesions. The skin lesions are characterized by proinflammatory cytokines and growth factors as well as inflammatory hypoxia, creating a stressful microenvironment for Mø. Of importance, not all Mø in lesions harbor parasites. To distinguish the influence of the parasite from the inflammatory microenvironment after Leishmania major (LM) infection on the Mø, we performed single-cell RNA sequencing and compared Mø associated with LM transcripts (or 'infected' Mø) with Mø not associated with LM transcripts (or 'bystander' Mø) within the lesions. Our findings show coordinated lysosomal expression and regulation signaling with increased cathepsin and H+-ATPase transcripts are upregulated in infected compared with bystander Mø. Additionally, eukaryotic initiation factor 2 (EIF2) signaling is downregulated in infected compared with bystander Mø, which includes many small and large ribosomal subunit (Rps and Rpl) transcripts being decreased in Mø harboring parasites. Furthermore, we also find EIF2 signaling including EIF, Rps, and Rpl transcripts being downregulated in bystander Mø compared with Mø from naïve skin. These data suggest that both the parasite and the inflammatory host microenvironment affect the transcription of ribosomal machinery in lesional Mø, thereby potentially affecting the ability of these cells to perform translation, protein synthesis, and thus function. Altogether, these results suggest that both the parasite and host inflammatory microenvironment independently drive transcriptional remodeling in Mø during LM infection in vivo.

Investigation of translation initiation factor through protein–protein interactions and molecular dynamics approaches

ABSTRACT A crucial biological process that involves both transcription and translation is protein synthesis. While, the translation mechanism endures protein synthesis with the help of messenger RNA, translation initiation factors, initiator tRNA and ribosomal small subunit, which efficiently recruit mRNA and start protein synthesis. This study focuses on the archaea, which is an attractive target of its evolutionary aspects. aIF2 plays a key regulatory roles in the archaea. This work mainly focuses on the initiation mechanism of Pyrococcus horikoshii OT3 and analyzes the structural interaction pattern between proteins. Here, the crystal structure of PH0702 was retrieved from the Protein Data Bank (PDB id: 6A34). Further, a molecular docking was carried out with the PH0702 protein, GTP and tRNA using the Glide module of Schrödinger and PATCHDOCK online server. Result shows the residues (Arg57, Gln206 and Lys258) interact with the oxygen group of 1st, 2nd and 3rd phosphoric acid. The three hydrogen bonds were formed between the Guanine (560) and Ser (300). Similarly, Modeling of 30S ribosomal subunit and mRNA of P. horikoshii OT3 were carried and their stability was analyzed using the molecular dynamics approach. Hence, this study paved a good platform for elucidating the overall mechanism of the protein initiation process.

(2955) Proposal to conserve the name Didymium against Mucilago and Spumaria (Physarales, Myxomycetes)

(2955) Proposal to conserve the name <i>Didymium</i> against <i>Mucilago</i> and <i>Spumaria</i> (<i>Physarales</i>, <i>Myxomycetes</i>)

Ribosomal Protein uS5 and Friends: Protein-Protein Interactions Involved in Ribosome Assembly and Beyond.

Ribosomal proteins are fundamental components of the ribosomes in all living cells. The ribosomal protein uS5 (Rps2) is a stable component of the small ribosomal subunit within all three domains of life. In addition to its interactions with proximal ribosomal proteins and rRNA inside the ribosome, uS5 has a surprisingly complex network of evolutionarily conserved non-ribosome-associated proteins. In this review, we focus on a set of four conserved uS5-associated proteins: the protein arginine methyltransferase 3 (PRMT3), the programmed cell death 2 (PDCD2) and its PDCD2-like (PDCD2L) paralog, and the zinc finger protein, ZNF277. We discuss recent work that presents PDCD2 and homologs as a dedicated uS5 chaperone and PDCD2L as a potential adaptor protein for the nuclear export of pre-40S subunits. Although the functional significance of the PRMT3-uS5 and ZNF277-uS5 interactions remain elusive, we reflect on the potential roles of uS5 arginine methylation by PRMT3 and on data indicating that ZNF277 and PRMT3 compete for uS5 binding. Together, these discussions highlight the complex and conserved regulatory network responsible for monitoring the availability and the folding of uS5 for the formation of 40S ribosomal subunits and/or the role of uS5 in potential extra-ribosomal functions.

Full Profiling of GE81112A, an Underexplored Tetrapeptide Antibiotic with Activity against Gram-Negative Pathogens.

After the first total synthesis combined with structure revision, we performed thorough in vitro and in vivo profiling of the underexplored tetrapeptide GE81112A. From the determination of the biological activity spectrum and physicochemical and early absorption-distribution-metabolism-excretion-toxicity (eADMET) properties, as well as in vivo data regarding tolerability and pharmacokinetics (PK) in mice and efficacy in an Escherichia coli-induced septicemia model, we were able to identify the critical and limiting parameters of the original hit compound. Thus, the generated data will serve as the basis for further compound optimization programs and developability assessments to identify candidates for preclinical/clinical development derived from GE81112A as the lead structure. IMPORTANCE The spread of antimicrobial resistance (AMR) is becoming a more and more important global threat to human health. With regard to current medical needs, penetration into the site of infection represents the major challenge in the treatment of infections caused by Gram-positive bacteria. Considering infections associated with Gram-negative bacteria, resistance is a major issue. Obviously, novel scaffolds for the design of new antibacterials in this arena are urgently needed to overcome this crisis. Such a novel potential lead structure is represented by the GE81112 compounds, which inhibit protein synthesis by interacting with the small 30S ribosomal subunit using a binding site distinct from that of other known ribosome-targeting antibiotics. Therefore, the tetrapeptide antibiotic GE81112A was chosen for further exploration as a potential lead for the development of antibiotics with a new mode of action against Gram-negative bacteria.

Integration of miRNA and mRNA analysis reveals the role of ribosome in to anti-artificial aging in sweetcorn

Sweetcorn is a kind of maize with high sugar content and has poor seed aging tolerance, which seriously limits its production. However, few studies have explored the artificial aging (AA) tolerance by miRNA-mRNA integration analysis in sweetcorn. Here, we characterized the physiological, biochemical and transcriptomic changes of two contrasting lines K62 and K107 treated with AA during time series. Both the germination indexes and antioxidant enzymes showed significant difference between two lines. The MDA content of AA-tolerant genotype K62 was significantly lower than that of K107 on the fourth and sixth day. Subsequently, 157 differentially expressed miRNAs (DEMIs) and 8878 differentially expressed mRNAs (DEMs) were identified by RNA-seq analysis under aging stress. The “ribosome” and “peroxisome” pathways were enriched to respond to aging stress, genes for both large units and small ribosomal subunits were significantly upregulated expressed and higher translation efficiency might exist in K62. Thirteen pairs of miRNA-target genes were obtained, and 8 miRNA-mRNA pairs might involve in ribosome protein and translation process. Our results elucidate the mechanism of sweetcorn response to AA at miRNA-mRNA level, and provide a new insight into sweetcorn AA response to stress.