A conserved long-distance telomeric silencing mechanism suppresses mTOR signaling in aging human fibroblasts

Telomeres are repetitive nucleotide sequences at the ends of each chromosome. It has been hypothesized that telomere attrition evolved as a tumor suppressor mechanism in large long-lived species. Long telomeres can silence genes millions of bases away through a looping mechanism called telomere position effect over long distances (TPE-OLD). The function of this silencing mechanism is unknown. We determined a set of 2322 genes with high positional conservation across replicatively aging species that includes known and candidate TPE-OLD genes that may mitigate potentially harmful effects of replicative aging. Notably, we identified PPP2R2C as a tumor suppressor gene, whose up-regulation by TPE-OLD in aged human fibroblasts leads to dephosphorylation of p70S6 kinase and mammalian target of rapamycin suppression. A mechanistic link between telomeres and a tumor suppressor mechanism supports the hypothesis that replicative aging fulfills a tumor suppressor function and motivates previously unknown antitumor and antiaging strategies

Ozone- and ethylene-induced regulation of a grapevine resveratrol synthase promoter in transgenic tobacco.

Stilbene synthases (STSs) are enzymes that play a critical role in the biosynthesis of stilbene, phytoalexins in a small number of unrelated plant species, and are induced by various biotic and abiotic stressors like pathogen attack, UV-irradiation or ozone exposure. To investigate the molecular basis for ozone-induced plant stress responses, we have examined the promoter of the grapevine resveratrol synthase (Vst1). In this report we summarize the influence of ozone on gene regulation. In transgenic tobacco a chimeric gene construct, containing the Vst1 promoter combined with the β-glucuronidase (GUS) reporter gene, is rapidly induced by ozone (0.1 µl·l−1, 12 h). The same construct is also strongly induced by ethylene (20 µl·l−1, 12 h). Promoter deletion analysis of the 5′ flanking sequence identified a positive regulatory element between −430 bp and −280 bp. This region contains ethylene-responsive enhancer elements, as well as an elicitor-responsive sequence in inverse orientation

Ethylene- and ozone-induced regulation of a grapevine resveratrol synthase gene: Different responsive promoter regions.

Stilbene synthases (STSs) are enzymes that play a critical role in the biosynthesis of stilbenes, phytoalexins that are induced by various biotic and abiotic stressors like pathogen attack, UV radiation or ozone exposure. To investigate the molecular basis for ozone- and ethylene-induced plant stress responses, we analysed the full size promoter of the grapevine resveratrol synthase gene (Vst1). Transgenic tobacco plants harbouring a Vst1 promoter::beta-glucuronidase (GUS) reporter construct showed an increased GUS activity upon ozone (0.3 mul l(-1), 8 h) or ethylene (10 mul l(-1), 8 h) treatment. Using the fluorimetric GUS assay, deletion analysis of the 5'-flanking sequence identified a minimal ethylene-responsive region between -280 and -40 by upstream of the translation start codon. This region differs from the ozone-responsive Vst1 promoter region, suggesting that ethylene is not directly involved in signalling ozone-induced stilbene biosynthesis

Ozone-induced gene expression occurs via ethylene-dependent and -independent signalling.

Recent studies suggest that ethylene is involved in signalling ozone-induced gene expression. We show here that application of ozone increased glucuronidase (GUS) expression of chimeric reporter genes regulated by the promoters of the tobacco class I beta-1,3-glucanases (GLB and Gln2) and the grapevine resveratrol synthase (Vst1) genes in transgenic tobacco leaves. 5'-deletion analysis of the class I beta-1,3-glucanase promoter revealed that ozone-induced gene regulation is mainly mediated by the distal enhancer region containing the positively acting ethylene-responsive element (ERE). In addition, application of 1-methylcyclopropene (1-MCP), an inhibitor of ethylene action, blocked ozone-induced class I beta-1,3-glucanase promoter activity. Enhancer activity and ethylene-responsiveness depended on the integrity of the GCC boxes, cis-acting elements present in the ERE of the class I beta-1,3-glucanase and the basic-type pathogenesis-related PR-1 protein (PRB-1b) gene promoters. The minimal PRB-1b promoter containing only the ERE with intact GCC boxes, was sufficient to confer 10-fold ozone inducibility to a GUS-reporter gene, while a substitution mutation in the GCC box abolished ozone responsiveness. The ERE region of the class I beta-1,3-glucanase promoter containing two intact GCC boxes confered strong ozone inducibility to a minimal cauliflower mosaic virus (CaMV) 35S RNA promoter, whereas two single-base substitution in the GCC boxes resulted in a complete loss of ozone inducibility. Taken together, these datastrongly suggest that ethylene is signalling ozone-induced expression of class I beta-l,3-glucanase and PRB-1b genes. Promoter analysis of the stilbene synthase Vst1 gene unravelled different regions for ozone and ethylene-responsiveness. Application of 1-MCP blocked ethylene-induced Vst1 induction, but ozone induction was not affected. This shows that ozone-induced gene expression occurs via at least two different signalling mechanisms and suggests an additional ethylene independent signalling pathway for ozone-induced expression of genes involved in phytoalexin biosynthesis

Síntese de trans-resveratrol e controle de podridão em maçãs com uso de elicitores em pós-colheita Synthesis of trans-resveratrol and rotting control in apples with use of elicitors in post-harvest

O objetivo deste trabalho foi avaliar o efeito da aplicação de elicitores abióticos na biossíntese de resveratrol e na indução de resistência à podridão póscolheita de maçãs 'Gala' e 'Fuji'. Foram realizados os tratamentos: radiação ultravioleta, fosfito e acibenzolar-Smetil - aplicados antes do armazenamento - e ozônio - aplicado intermitente durante o armazenamento. As condições de armazenamento foram: 'Gala', 1,5 kPa de O2 e 2,5 kPa de CO2, a 0,5±0,1ºC, por oito meses, e 'Fuji', 1,0 kPa de O2 e <0,5 kPa de CO2, a 0,5±0,1ºC, por sete meses. O delineamento experimental foi inteiramente ao acaso, com oito repetições de 25 frutos. Na casca dos frutos, determinou-se: trans-resveratrol, polifenóis totais, antocianinas totais e diâmetro de lesão, após inoculação de Penicillium sp. no ferimento. Analisou-se na polpa: firmeza de polpa, acidez titulável, sólidos solúveis totais, açúcares redutores e nãoredutores. Os elicitores não alteram a concentração de polifenóis totais e antocianinas, com exceção do acibenzolar-Smetil que reduz o conteúdo de antocianinas na maçã 'Gala'. Os elicitores induzem, na 'Fuji', mas não na maçã 'Gala', a síntese de trans-resveratrol na seqüência: acibenzolar-Smetil> fosfito> irradiação UV-C> ozônio. Na maçã 'Gala', o fosfito reduz a ocorrência de podridão, porém, em ambas as cultivares, não há correlação entre síntese de trans-resveratrol e controle de podridão.<br>The objective of this study was evaluate the effect of the application of abiotic elicitors of resveratrol in 'Gala' and 'Fuji' apples, and rotting control. The treatment was with ultraviolet irradiation, phosphite and acibenzolar-Smethyl, applied before controlled atmosphere storage and ozone, applied so intermittently during storage. The storage conditions were: 'Gala' (1.5 kPa O2 and 2.5 kPa CO2, at 0.5±0.1°C by eight months) and 'Fuji' (1.0 kPa O2 and <0.5 kPa CO2, at 0.5±0.1°C for seven months). The experimental design was a completely randomized with eight repetitions of 25 fruits. In the skin of fruit trans-resveratrol were analyzed by high performance liquid chromatography; total polyphenols and anthocyanins by spectrophotometry and diameter of injury after inoculation by Penicillium sp. Firmness, acidity, total soluble solids, and reducing and nonreducing sugars were analyzed in the flesh. The elicitores do not change the concentration of phenols and anthocyanins, with the exception of the loss of total anthocyanins with acibenzolar-Smethyl in 'Gala' apple. The elicitors induce in 'Fuji' apples the synthesis of trans-resveratrol in the sequence: acibenzolar-Smethyl>phosphite>UV-C irradiation>ozone. There isn't correlation between synthesis of trans-resveratrol and rotting control, but the phosphite controlled rot in 'Gala'