Karyopherin Kap114p-mediated trans-repression controls ribosomal gene expression under saline stress.
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ABSTRACT:
SUBMITTER: Liao CC
PROVIDER: S-EPMC7332979 | biostudies-literature |
REPOSITORIES: biostudies-literature
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Project description:Gcn4p is a well-characterized bZIP transcription factor that activates more than 500 genes encoding amino acids and purine biosynthesis enzymes, and many stress-response genes under various stress conditions. Under these stresses, it had been shown that transcriptions of ribosomal protein (RP) genes were decreased. However, the detailed mechanism of this downregulation has not been elucidated. In this study, we present a novel mechanistic model for a repressive role of Gcn4p on RP transcription, especially under amino-acid starvation. It was found that Gcn4p bound directly to Rap1p, which in turn inhibited Esa1p-Rap1p binding. The inhibition of Esa1p recruitment to RP promoters ultimately reduced the level of histone H4 acetylation and RP transcription. These data revealed that Gcn4p has simultaneous dual roles as a repressor for RP genes as well as an activator for amino-acid biosynthesis genes. Moreover, our results showed evidence of a novel link between general control of amino-acid biosynthesis and ribosome biogenesis mediated by Gcn4p at an early stage of adaptation to amino-acid starvation.
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Project description:Plant growth is plastic, able to rapidly adjust to fluctuation in environmental conditions such as drought and salinity. Due to long-term irrigation use in agricultural systems, soil salinity is increasing; consequently crop yield is adversely affected. It is known that salt tolerance is a quantitative trait supported by genes affecting ion homeostasis, ion transport, ion compartmentalization and ion selectivity. Less is known about pathways connecting NaCl and cell proliferation and cell death. Plant growth and cell proliferation is, in part, controlled by the concerted activity of the heterotrimeric G-protein complex with glucose. Prompted by the abundance of stress-related, functional annotations of genes encoding proteins that interact with core components of the Arabidopsis heterotrimeric G protein complex (AtRGS1, AtGPA1, AGB1, and AGG), we tested the hypothesis that G proteins modulate plant growth under salt stress.Na+ activates G signaling as quantitated by internalization of Arabidopsis Regulator of G Signaling protein 1 (AtRGS1). Despite being components of a singular signaling complex loss of the G? subunit (agb1-2 mutant) conferred accelerated senescence and aborted development in the presence of Na+, whereas loss of AtRGS1 (rgs1-2 mutant) conferred Na+ tolerance evident as less attenuated shoot growth and senescence. Site-directed changes in the G? and G?? protein-protein interface were made to disrupt the interaction between the G? and G?? subunits in order to elevate free activated G? subunit and free G?? dimer at the plasma membrane. These mutations conferred sodium tolerance. Glucose in the growth media improved the survival under salt stress in Col but not in agb1-2 or rgs1-2 mutants.These results demonstrate a direct role for G-protein signaling in the plant growth response to salt stress. The contrasting phenotypes of agb1-2 and rgs1-2 mutants suggest that G-proteins balance growth and death under salt stress. The phenotypes of the loss-of-function mutations prompted the model that during salt stress, G activation promotes growth and attenuates senescence probably by releasing ER stress.
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Project description:BackgroundSaline-alkaline stress is a major abiotic stress that is harmful to plant growth worldwide. Two peach cultivars (GF677 and Maotao) display distinct phenotypes under saline-alkaline stress. The molecular mechanism explaining the differences between the two cultivars is still unclear.ResultsIn the present study, we systematically analysed the changes in GF677 and Maotao leaves upon saline-alkaline stress by using cytological and biochemical technologies as well as comparative transcriptome analysis. Transmission electron microscopy (TEM) observations showed that the structure of granum was dispersive in Maotao chloroplasts. The biochemical analysis revealed that POD activity and the contents of chlorophyll a and chlorophyll b, as well as iron, were notably decreased in Maotao. Comparative transcriptome analysis detected 881 genes with differential expression (including 294 upregulated and 587 downregulated) under the criteria of |log2 Ratio| ≥ 1 and FDR ≤0.01. Gene ontology (GO) analysis showed that all differentially expressed genes (DEGs) were grouped into 30 groups. MapMan annotation of DEGs showed that photosynthesis, antioxidation, ion metabolism, and WRKY TF were activated in GF677, while cell wall degradation, secondary metabolism, starch degradation, MYB TF, and bHLH TF were activated in Maotao. Several iron and stress-related TFs (ppa024966m, ppa010295m, ppa0271826m, ppa002645m, ppa010846m, ppa009439m, ppa008846m, and ppa007708m) were further discussed from a functional perspective based on the phylogenetic tree integration of other species homologues.ConclusionsAccording to the cytological and molecular differences between the two cultivars, we suggest that the integrity of chloroplast structure and the activation of photosynthesis as well as stress-related genes are crucial for saline-alkaline resistance in GF677. The results presented in this report provide a theoretical basis for cloning saline-alkaline tolerance genes and molecular breeding to improve saline-alkaline tolerance in peach.
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Project description:The rice cultivar (Oryza sativa L.) BRS AG, developed by Embrapa Clima Temperado, is the first cultivar designed for purposes other than human consumption. It may be used in ethanol production and animal feed. Different abiotic stresses negatively affect plant growth. Soil salinity is responsible for a serious reduction in productivity. Therefore, the objective of this study was to evaluate the gene expression and the activity of antioxidant enzymes (SOD, CAT, APX and GR) and identify their functions in controlling ROS levels in rice plants, cultivar BRS AG, after a saline stress period. The plants were grown in vitro with two NaCl concentrations (0 and 136 mM), collected at 10, 15 and 20 days of cultivation. The results indicated that the activity of the enzymes evaluated promotes protection against oxidative stress. Although, there was an increase of reactive oxygen species, there was no increase in MDA levels. Regarding genes encoding isoforms of antioxidant enzymes, it was observed that OsSOD3-CU/Zn, OsSOD2-Cu/Zn, OsSOD-Cu/Zn, OsSOD4-Cu/Zn, OsSODCc1-Cu/Zn, OsSOD-Fe, OsAPX1, OsCATB and OsGR2 were the most responsive. The increase in the transcription of all genes among evaluated isoforms, except for OsAPX6, which remained stable, contributed to the increase or the maintenance of enzyme activity. Thus, it is possible to infer that the cv. BRS AG has defense mechanisms against salt stress.
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Project description:BackgroundSoybean is an important oilseed crop that its development and production are affected by environmental stresses (such as saline-alkaline and water deficit).ObjectivesThis experiment was performed with the aim of identifying candidate genes in saline-alkaline stress and water-deficit stress conditions using transcriptome analysis and to investigate the expression of these genes under water deficit stress conditions using RTqPCR.Materials and methodsIn this experiment, soybean transcriptome data under saline-alkaline and water-deficit stress were downloaded from the NCBI website, and then the co-expression modules were determined for them and the gene network was plotted for each module, and finally, the hub genes were identified. To compare the expression of genes in saline-alkaline and water deficit conditions, soybean plants were subjected to water deficit stress and their gene expression was determined using RTqPCR.ResultsThe filtered (Log FC above +2 and below -2) genes of soybean were grouped under saline-alkaline stress in 15 modules and under water-deficit stress in 2 different modules. Within each module, the interaction of genes was identified using the gene network, then three genes of ann11, cyp450 and zfp selected as hub genes. These hub genes are highly co-expression with other network genes, which not only display differential expression but also differential co-expression. The results of RT-PCR indicated that cyp450 gene expression was not significantly different from the control, while ann11 gene expression significantly increased under water deficit stress, but zfp gene expression decreased significantly under water deficit stress.ConclusionsWe identified three genes, ann11, cyp450 and zfp, as hub genes. According to our results, ann11 gene had a significant increase in expression under water deficit stress, which can indicate the importance of this gene under drought conditions. Therefore, according to the results of this experiment as well as other researchers, we introduce this gene as a key gene in water deficit tolerance and recommend its use in genetic engineering to increase the tolerance of other plants.
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Project description:The expression of ribosomal protein (RP) genes requires a substantial part of cellular transcription, processing and translation resources. Thus, the RP expression must be tightly regulated in response to conditions that compromise cell survival. In Saccharomyces cerevisiae cells, regulation of the RP gene expression at the transcriptional, mature mRNA stability and translational levels during the response to osmotic stress has been reported. Reprogramming global protein synthesis upon osmotic shock includes the movement of ribosomes from RP transcripts to stress-induced mRNAs. Using tiling arrays, we show that osmotic stress yields a drop in the levels of RP pre-mRNAs in S. cerevisiae cells. An analysis of the tiling array data, together with transcription rates data, shows a poor correlation, indicating that the drop in the RP pre-mRNA levels is not merely a result of the lowered RP transcription rates. A kinetic study using quantitative RT-PCR confirmed the decrease in the levels of several RP-unspliced transcripts during the first 15 minutes of osmotic stress, which seems independent of MAP kinase Hog1. Moreover, we found that the mutations in the components of the nonsense-mediated mRNA decay (NMD), Upf1, Upf2, Upf3 or in exonuclease Xrn1, eliminate the osmotic stress-induced drop in RP pre-mRNAs. Altogether, our results indicate that the degradation of yeast RP unspliced transcripts by NMD increases during osmotic stress, and suggest that this might be another mechanism to control RP synthesis during the stress response.
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Project description:Transcription factor IIS (TFIIS) stimulates RNA cleavage by RNA polymerase II by allowing backtracked enzymes to resume transcription elongation. Yeast cells do not require TFIIS for viability, unless they suffer severe transcriptional stress due to NTP-depleting drugs like 6-azauracil or mycophenolic acid. In order to broaden our knowledge on the role of TFIIS under transcriptional stress, we carried out a genetic screening for suppressors of TFIIS-lacking cells' sensitivity to 6-azauracil and mycophenolic acid. Five suppressors were identified, four of which were related to the transcriptional regulation of those genes encoding ribosomal components [rRNAs and ribosomal proteins (RP)], including global regulator SFP1. This led us to discover that RNA polymerase II is hypersensitive to the absence of TFIIS under NTP scarcity conditions when transcribing RP genes. The absence of Sfp1 led to a profound alteration of the transcriptional response to NTP-depletion, thus allowing the expression of RP genes to resist these stressful conditions in the absence of TFIIS. We discuss the effect of transcriptional stress on ribosome biogenesis and propose that TFIIS contributes to prevent a transcriptional imbalance between rDNA and RP genes.
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Project description:Gene expression is modulated by both physiological signals (hormones, cytokines, etc.) and environmental stimuli (physical parameters, xenobiotics, etc.). Oxidative stress appears to be a key pleiotropic modulator which may be involved in either pathway. Indeed, reactive oxygen species (ROS) have been described as second messengers for several growth factors and cytokines, but have also been shown to rise following cellular insults such as xenobiotic metabolism or enzymic deficiency. Extensive studies on the induction of stress-response genes by oxidative stress have been reported. In contrast, owing to the historical focus on gene induction, less attention has been paid to gene repression by ROS. However, a growing number of studies have shown that moderate (i.e. non-cytotoxic) oxidative stress specifically down-regulates the expression of various genes. In this review, we describe the alteration of several physiological functions resulting from oxidative-stress-mediated inhibition of gene transcription. We will then focus on the repressive oxidative modulation of various transcription factors elicited by ROS.
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