scholarly journals Early Transcriptional Response to DNA Virus Infection in Sclerotinia sclerotiorum

Viruses ◽  
2019 ◽  
Vol 11 (3) ◽  
pp. 278 ◽  
Author(s):  
Feng Ding ◽  
Jiasen Cheng ◽  
Yanping Fu ◽  
Tao Chen ◽  
Bo Li ◽  
...  
Keyword(s):  
Signal Transduction ◽  
G Protein ◽  
Sclerotinia Sclerotiorum ◽  
Molecular Mechanisms ◽  
Cell Structure ◽  
Differentially Expressed ◽  
Post Inoculation ◽  
Dna Virus ◽  
Fungal Cell ◽  
Small G Protein

We previously determined that virions of Sclerotinia sclerotiorum hypovirulence associated DNA virus 1 (SsHADV-1) could directly infect hyphae of Sclerotinia sclerotiorum, resulting in hypovirulence of the fungal host. However, the molecular mechanisms of SsHADV-1 virions disruption of the fungal cell wall barrier and entrance into the host cell are still unclear. To investigate the early response of S. sclerotiorum to SsHADV-1 infection, S. sclerotiorum hyphae were inoculated with purified SsHADV-1 virions. The pre- and post-infection hyphae were collected at one–three hours post-inoculation for transcriptome analysis. Further, bioinformatic analysis showed that differentially expressed genes (DEGs) regulated by SsHADV-1 infection were identified in S. sclerotiorum. In total, 187 genes were differentially expressed, consisting of more up-regulated (114) than down-regulated (73) genes. The identified DEGs were involved in several important pathways. Metabolic processes, biosynthesis of antibiotics, and secondary metabolites were the most affected categories in S. sclerotiorum upon SsHADV-1 infection. Cell structure analysis suggested that 26% of the total DEGs were related to membrane tissues. Furthermore, 10 and 27 DEGs were predicted to be located in the cell membrane and mitochondria, respectively. Gene ontology enrichment analyses of the DEGs were performed, followed by functional annotation of the genes. Interestingly, one third of the annotated functional DEGs could be involved in the Ras-small G protein signal transduction pathway. These results revealed that SsHADV-1 virions may be able to bind host membrane proteins and influence signal transduction through Ras-small G protein-coupled receptors during early infection, providing new insight towards the molecular mechanisms of virions infection in S. sclerotiorum.

scholarly journals Global Gene Responses of Resistant and Susceptible Sugarcane Cultivars to Acidovorax avenae subsp. avenae Identified Using Comparative Transcriptome Analysis

2019 ◽  
Vol 8 (1) ◽  
pp. 10 ◽  
Author(s):  
Na Chu ◽  
Jing-Ru Zhou ◽  
Hua-Ying Fu ◽  
Mei-Ting Huang ◽  
Hui-Li Zhang ◽  
...  
Keyword(s):  
Signal Transduction ◽  
Large Scale ◽  
Molecular Mechanisms ◽  
Expression Patterns ◽  
Defense Responses ◽  
Differentially Expressed ◽  
Mitogen Activated Protein Kinase ◽  
Post Inoculation ◽  
Rna Seq ◽  
Mitogen Activated Protein

Red stripe disease in sugarcane caused by Acidovorax avenae subsp. avenae (Aaa) is related to serious global losses in yield. However, the underlying molecular mechanisms associated with responses of sugarcane plants to infection by this pathogen remain largely unknown. Here, we used Illumina RNA-sequencing (RNA-seq) to perform large-scale transcriptome sequencing of two sugarcane cultivars to contrast gene expression patterns of plants between Aaa and mock inoculations, and identify key genes and pathways involved in sugarcane defense responses to Aaa infection. At 0–72 hours post-inoculation (hpi) of the red stripe disease-resistant cultivar ROC22, a total of 18,689 genes were differentially expressed between Aaa-inoculated and mock-inoculated samples. Of these, 8498 and 10,196 genes were up- and downregulated, respectively. In MT11-610, which is susceptible to red stripe disease, 15,782 genes were differentially expressed between Aaa-inoculated and mock-inoculated samples and 8807 and 6984 genes were up- and downregulated, respectively. The genes that were differentially expressed following Aaa inoculation were mainly involved in photosynthesis and carbon metabolism, phenylpropanoid biosynthesis, plant hormone signal transduction, and plant–pathogen interaction pathways. Further, qRT-PCR and RNA-seq used for additional validation of 12 differentially expressed genes (DEGs) showed that eight genes in particular were highly expressed in ROC22. These eight genes participated in the biosynthesis of lignin and coumarin, as well as signal transduction by salicylic acid, jasmonic acid, ethylene, and mitogen-activated protein kinase (MAPK), suggesting that they play essential roles in sugarcane resistance to Aaa. Collectively, our results characterized the sugarcane transcriptome during early infection with Aaa, thereby providing insights into the molecular mechanisms responsible for bacterial tolerance.

scholarly journals Identification of Differentially Expressed Proteins in Sugarcane in Response to Infection by Xanthomonas albilineans Using iTRAQ Quantitative Proteomics

2020 ◽  
Vol 8 (1) ◽  
pp. 76
Author(s):  
Jian-Yu Meng ◽  
Mbuya Sylvain Ntambo ◽  
Philippe C. Rott ◽  
Hua-Ying Fu ◽  
Mei-Ting Huang ◽  
...  
Keyword(s):  
Molecular Mechanisms ◽  
Vascular System ◽  
Lipid Transfer Protein ◽  
Differentially Expressed ◽  
Post Inoculation ◽  
Differentially Expressed Proteins ◽  
Lipid Transfer ◽  
Leaf Scald ◽  
Improvement Programs ◽  
Xanthomonas Albilineans

Sugarcane can suffer severe yield losses when affected by leaf scald, a disease caused by Xanthomonas albilineans. This bacterial pathogen colonizes the vascular system of sugarcane, which can result in reduced plant growth and plant death. In order to better understand the molecular mechanisms involved in the resistance of sugarcane to leaf scald, a comparative proteomic study was performed with two sugarcane cultivars inoculated with X. albilineans: one resistant (LCP 85-384) and one susceptible (ROC20) to leaf scald. The iTRAQ (isobaric tags for relative and absolute quantification) approach at 0 and 48 h post-inoculation (hpi) was used to identify and annotate differentially expressed proteins (DEPs). A total of 4295 proteins were associated with 1099 gene ontology (GO) terms by GO analysis. Among those, 285 were DEPs during X. albilineans infection in cultivars LCP 85-384 and ROC20. One hundred seventy-two DEPs were identified in resistant cultivar LCP 85-384, and 113 of these proteins were upregulated and 59 were downregulated. One hundred ninety-two DEPs were found in susceptible cultivar ROC20 and half of these (92) were upregulated, whereas the other half corresponded to downregulated proteins. The significantly upregulated DEPs in LCP 85-384 were involved in metabolic pathways, the biosynthesis of secondary metabolites, and the phenylpropanoid biosynthesis pathway. Additionally, the expression of seven candidate genes related to photosynthesis and glycolytic pathways, plant innate immune system, glycosylation process, plant cytochrome P450, and non-specific lipid transfer protein was verified based on transcription levels in sugarcane during infection by X. albilineans. Our findings shed new light on the differential expression of proteins in sugarcane cultivars in response to infection by X. albilineans. The identification of these genes provides important information for sugarcane variety improvement programs using molecular breeding strategies.

scholarly journals Transcriptome Analysis of Cinnamomum Migao Seed Germination in Medicinal Plants of Southwest China

2020 ◽  
Author(s):  
xiaolong Huang ◽  
Tian Tian ◽  
Jingzhong Chen ◽  
Deng Wang ◽  
Bingli Tong ◽  
...  
Keyword(s):  
Seed Germination ◽  
Transcriptome Analysis ◽  
Energy Supply ◽  
Molecular Mechanisms ◽  
Tricarboxylic Acid Cycle ◽  
Cell Structure ◽  
Seed Vigor ◽  
Differentially Expressed ◽  
Oil Bodies ◽  
Physiological Indexes

Abstract Background: Cinnamomum migao is an endangered evergreen woody plant species endemic to China. Its fruit is used as a traditional medicine by the Miao nationality of China and has a high commercial value. However, its seed germination rate is very low under natural and artificial conditions. As the foundation of plant propagation, seed germination involves a series of physiological, cellular, and molecular changes; however, the molecular events and systematic changes occurring during C. migao seed germination remain unclear.Results: In this study, combined with the changes in physiological indexes and transcription levels, we revealed the regulation characteristic of cell structures, storage substances, and antioxidant capacity during seed germination. Anatomical analysis revealed that abundant smooth and full oil bodies were present in the cotyledons of the seeds. With seed germination, the oil bodies and other substances gradually degraded to supply energy; this was consistent with the content of storage substances. In parallel to anatomical and physiological analyses, transcriptome analysis showed that 80%–90% of differentially expressed genes (DEGs) appeared after seed imbibition, reflecting important development and physiological changes. The unigenes involved in material metabolism (glycerolipid metabolism, fatty acid degradation, and starch and sucrose metabolism) and energy supply pathways (pentose phosphate pathway, glycolysis pathway, pyruvate metabolism, tricarboxylic acid cycle, and oxidative phosphorylation) were differentially expressed in the four germination stages. Among these DEGs, a small number of genes in the energy supply pathway at the initial stage of germination maintained high level of expression to maintain seed vigor and germination ability. Then, the genes involved in lipid metabolism were activated at a large scale, followed by the activation of the genes involved in CHO metabolism, which had its own species specificity. Conclusions: Our study revealed the transcriptional levels of genes during seed germination as well as determined the order of the metabolic pathways. The changes in cell structure and physiological indexes also confirmed these events. Our findings lay a foundation for determining the molecular mechanisms underlying seed germination.

scholarly journals fIdentification of B. napus small RNAs responsive to infection by a necrotrophic pathogen

2021 ◽  
Vol 21 (1) ◽  
Author(s):  
Roshan Regmi ◽  
Toby E. Newman ◽  
Lars G. Kamphuis ◽  
Mark C. Derbyshire
Keyword(s):  
Disease Resistance ◽  
Small Rnas ◽  
Molecular Mechanisms ◽  
High Throughput Sequencing ◽  
Differentially Expressed ◽  
Disease Resistance Gene ◽  
Ethylene Response Factor ◽  
Post Inoculation ◽  
Necrotrophic Pathogen ◽  
Degradome Sequencing

Abstract Background Small RNAs are short non-coding RNAs that are key gene regulators controlling various biological processes in eukaryotes. Plants may regulate discrete sets of sRNAs in response to pathogen attack. Sclerotinia sclerotiorum is an economically important pathogen affecting hundreds of plant species, including the economically important oilseed B. napus. However, there are limited studies on how regulation of sRNAs occurs in the S. sclerotiorum and B. napus pathosystem. Results We identified different classes of sRNAs from B. napus using high throughput sequencing of replicated mock and infected samples at 24 h post-inoculation (HPI). Overall, 3999 sRNA loci were highly expressed, of which 730 were significantly upregulated during infection. These 730 up-regulated sRNAs targeted 64 genes, including disease resistance proteins and transcriptional regulators. A total of 73 conserved miRNA families were identified in our dataset. Degradome sequencing identified 2124 cleaved mRNA products from these miRNAs from combined mock and infected samples. Among these, 50 genes were specific to infection. Altogether, 20 conserved miRNAs were differentially expressed and 8 transcripts were cleaved by the differentially expressed miRNAs miR159, miR5139, and miR390, suggesting they may have a role in the S. sclerotiorum response. A miR1885-triggered disease resistance gene-derived secondary sRNA locus was also identified and verified with degradome sequencing. We also found further evidence for silencing of a plant immunity related ethylene response factor gene by a novel sRNA using 5′-RACE and RT-qPCR. Conclusions The findings in this study expand the framework for understanding the molecular mechanisms of the S. sclerotiorum and B. napus pathosystem at the sRNA level.

Multi-omics analysis of cellular pathways involved in different rapid growth stages of moso bamboo

2020 ◽  
Vol 40 (11) ◽  
pp. 1487-1508
Author(s):  
Gui-Yun Tao ◽  
Muthusamy Ramakrishnan ◽  
Kunnummal Kurungara Vinod ◽  
Kim Yrjälä ◽  
Viswanathan Satheesh ◽  
...  
Keyword(s):  
Signal Transduction ◽  
Rapid Growth ◽  
Ribosome Biogenesis ◽  
Molecular Mechanisms ◽  
Expression Profiles ◽  
Moso Bamboo ◽  
Differentially Expressed ◽  
Molecular Networks ◽  
Growth Stages ◽  
Cellular Pathways

Abstract Moso bamboo (Phyllostachys edulis (Carriere) J. Houzeau) is a rapidly growing grass of industrial and ecological importance. However, the molecular mechanisms of its remarkable growth are not well understood. In this study, we investigated the early-stage growth of moso bamboo shoots and defined three different growth stages based on histological and biochemical analyses, namely, starting of cell division (SD), rapid division (RD) and rapid elongation (RE). Further analyses on potentially relevant cellular pathways in these growth stages using multi-omics approaches such as transcriptomics and proteomics revealed the involvement of multiple cellular pathways, including DNA replication, repair and ribosome biogenesis. A total of 8045 differentially expressed genes (DEGs) and 1053 differentially expressed proteins (DEPs) were identified in our analyses. Gene Ontology and Kyoto Encyclopedia of Genes and Genomes enrichment analyses of detected DEGs identified several key biological pathways such as phytohormone metabolism, signal transduction, cell wall development and carbohydrate metabolism. The comparative analysis of proteins displayed that a total of 213 DEPs corresponded with DEGs and 3 significant expression profiles that could be promoting the fast growth of bamboo internodes. Moreover, protein–protein interaction network prediction analysis is suggestive of the involvement of five major proteins of signal transduction, DNA synthesis and RNA transcription, and may act as key elements responsible for the rapid shoot growth. Our work exploits multi-omics and bioinformatic approaches to unfurl the complexity of molecular networks involved in the rapid growth of moso bamboo and opens up questions related to the interactions between the functions played by individual molecular pathway.

scholarly journals Comparative Analysis of Transcriptome and sRNAs Expression Patterns in the Brachypodium distachyon— Magnaporthe oryzae Pathosystems

2021 ◽  
Vol 22 (2) ◽  
pp. 650
Author(s):  
Silvia Zanini ◽  
Ena Šečić ◽  
Tobias Busche ◽  
Matteo Galli ◽  
Ying Zheng ◽  
...  
Keyword(s):  
Magnaporthe Oryzae ◽  
Brachypodium Distachyon ◽  
Expression Patterns ◽  
Critical Role ◽  
Differentially Expressed ◽  
Post Inoculation ◽  
Plant Host ◽  
Fungal Cell ◽  
Fungal Virulence ◽  
Leaves And Roots

The hemibiotrophic fungus Magnaporthe oryzae (Mo) is the causative agent of rice blast and can infect aerial and root tissues of a variety of Poaceae, including the model Brachypodium distachyon (Bd). To gain insight in gene regulation processes occurring at early disease stages, we comparatively analyzed fungal and plant mRNA and sRNA expression in leaves and roots. A total of 310 Mo genes were detected consistently and differentially expressed in both leaves and roots. Contrary to Mo, only minor overlaps were observed in plant differentially expressed genes (DEGs), with 233 Bd-DEGs in infected leaves at 2 days post inoculation (DPI), compared to 4978 at 4 DPI, and 138 in infected roots. sRNA sequencing revealed a broad spectrum of Mo-sRNAs that accumulated in infected tissues, including candidates predicted to target Bd mRNAs. Conversely, we identified a subset of potential Bd-sRNAs directed against fungal cell wall components, virulence genes and transcription factors. We also show a requirement of operable RNAi genes from the DICER-like (DCL) and ARGONAUTE (AGO) families for fungal virulence. Overall, our work elucidates the extensive reprogramming of transcriptomes and sRNAs in both plant host (Bd) and fungal pathogen (Mo), further corroborating the critical role played by sRNA species in the establishment of the interaction and its outcome.

scholarly journals Genome-wide characterization of Rice Black Streaked Dwarf Virus-responsive genes in rice

2020 ◽  
Vol 5 (2) ◽  
pp. 66-82
Author(s):  
Wei Liu ◽  
◽  
Zhen Li ◽  
Qingguo Wang ◽  
Jiaowen Pan ◽  
...  
Keyword(s):  
Signal Transduction ◽  
Molecular Mechanisms ◽  
High Throughput Sequencing ◽  
Cell Structure ◽  
Brown Planthopper ◽  
Digital Gene Expression ◽  
Dwarf Virus ◽  
Rna Seq ◽  
Digital Gene Expression Profile ◽  
Dark Green

Background: Rice black streaked dwarf virus (RBSDV) is an important pathogen disease in rice and gramineous planting regions all over the world. The major phenotypes of RBSDV infected rice were dwarf with dark green leaves, which generally resulted in seriously loss of yield. The RBSDV known so far is preoperatively transmitted to rice in a persistent manner by small brown planthopper (SBPH), instead of transmitting to offspring through ovary. Results: To identify RBSDV responsive genes and to explore and clarify the molecular mechanisms involved in plant-virus interaction, digital gene expression profile (DGE) analysis was performed by high-throughput sequencing using wild-type (WT) and RBSDV infected rice leaves (IRL) as materials. A total of 165,975 and 165,940 unique tags were obtained in IRL and WT libraries, respectively. In comparison with the control, 896 differentially expressed genes (DEGs) were obtained, of which 500 DEGs were up regulated and 396 DEGs were down regulated. Functional analysis showed that DEGs mainly classified into10 groups, including metabolism, stress pathogen and defense, signal transduction, Transporter, transcription and post-transcription, cell structure and division etc. To further validate reliability and authenticity of the data, 10 DEGs were randomly picked and Real-time RT-PCR was carried out, and the expression trends of 7 genes were in line with the RNA-seq results. By searching the RBSDV related miRNA database of rice, 10 targeted genes of 6 significantly changed miRNAs were also identified in these DEGs. Conclusions: The data derived from RNA-seq were valid and credible. Through this research, a series of candidate RBSDV-responsive genes were obtained, and special signal transduction and metabolism pathways were built and pulled out in rice. This study provided further insight into the molecular mechanisms during compatible and incompatible interactions between viruses and their host plants.

scholarly journals Transcriptomics analysis reveals the signal transduction mechanism of brassinolides in tea leaves and its regulation on the growth and development of Camellia sinensis

BMC Genomics ◽  
2022 ◽  
Vol 23 (1) ◽  
Author(s):  
Qifang Jin ◽  
Zhong Wang ◽  
Yanni Chen ◽  
Yiping Luo ◽  
Na Tian ◽  
...  
Keyword(s):  
Signal Transduction ◽  
Differentially Expressed Genes ◽  
Camellia Sinensis ◽  
Growth And Development ◽  
Cell Structure ◽  
Enrichment Analysis ◽  
Differentially Expressed ◽  
Pathway Enrichment Analysis ◽  
Tea Leaves ◽  
Depth Analysis

Abstract Background Brassinosteroids (BRs) are a type of sterol plant hormone that play an important role in various biochemical and physiological reactions such as promoting cell growth, increasing biomass, and improving stress resistance. Results To investigate the regulatory and molecular mechanism of BRs on the growth and development of tea plants (Camellia sinensis L.), changes in cell structure and gene expression levels of tea leaves treated with exogenous BRs were analyzed by electron microscopy and high-throughput Illumina RNA-Seq technology. The results showed that the number of starch granules in the chloroplasts and lipid globules increased and thylakoids expanded after BR treatment compared with the control. Transcriptome analysis showed that in the four BR treatments (CAA: BR treatment for 3 h, CAB: BR treatment for 9 h, CAC: BR treatment for 24 h, and CAD: BR treatment for 48 h), 3861 (1867 upregulated and 1994 downregulated), 5030 (2461 upregulated and 2569 downregulated), 1626 (815 upregulated and 811 downregulated), and 2050 (1004 upregulated and 1046 downregulated) differentially expressed genes were detected, respectively, compared with CAK (BR treatment for 0 h). Using Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) databases, metabolic pathway enrichment analysis showed that the differentially expressed genes of CAA vs. CAK, CAB vs. CAK, CAC vs. CAK, and CAD vs. CAK significantly enriched the functional categories of signal transduction, cell cycle regulation, and starch, sucrose, and flavonoid biosynthesis and metabolism pathways. We also found that after spraying BR, the key genes for caffeine synthesis were downregulated. The results of qRT-PCR coincided with the findings of transcriptomic analysis. Conclusions The present study improved our understanding of the effects of BRs on the growth and development of tea leaves and laid the foundation for the in-depth analysis of signal transduction pathways of BRs in tea leaves.

scholarly journals Comparative transcriptomic analysis uncovers the complex genetic network for resistance to Sclerotinia sclerotiorum in Brassica napus

2016 ◽  
Vol 6 (1) ◽  
Author(s):  
Jian Wu ◽  
Qing Zhao ◽  
Qingyong Yang ◽  
Han Liu ◽  
Qingyuan Li ◽  
...  
Keyword(s):  
Brassica Napus ◽  
Differentially Expressed Genes ◽  
Sclerotinia Sclerotiorum ◽  
Defense Response ◽  
Quantitative Resistance ◽  
Resistance Breeding ◽  
Mapk Signaling ◽  
Differentially Expressed ◽  
Post Inoculation ◽  
Sclerotinia Stem Rot

Abstract Sclerotinia stem rot caused by Sclerotinia sclerotiorum is one of the most devastating diseases in many important crops including Brassica napus worldwide. Quantitative resistance is the only source for genetic improvement of Sclerotinia-resistance in B. napus, but the molecular basis for such a resistance is largely unknown. Here, we performed dynamic transcriptomic analyses to understand the differential defense response to S. sclerotiorum in a resistant line (R-line) and a susceptible line (S-line) of B. napus at 24, 48 and 96 h post-inoculation. Both the numbers of and fold changes in differentially expressed genes in the R-line were larger than those in the S-line. We identified 9001 relative differentially expressed genes in the R-line compared with the S-line. The differences between susceptibility and resistance were associated with the magnitude of expression changes in a set of genes involved in pathogen recognition, MAPK signaling cascade, WRKY transcription regulation, jasmonic acid/ethylene signaling pathways and biosynthesis of defense-related protein and indolic glucosinolate. The results were supported by quantitation of defense-related enzyme activity and glucosinolate contents. Our results provide insights into the complex molecular mechanism of the defense response to S. sclerotiorum in B. napus and for development of effective strategies in Sclerotinia-resistance breeding.

scholarly journals Alterations in myocardial signal transduction due to aging and chronic dynamic exercise

1998 ◽  
Vol 84 (1) ◽  
pp. 177-184 ◽  
Author(s):  
David A. Roth ◽  
Cynthia D. White ◽  
Deborah A. Podolin ◽  
Robert S. Mazzeo
Keyword(s):  
Signal Transduction ◽  
G Protein ◽  
Molecular Mechanisms ◽  
Middle Age ◽  
Age Groups ◽  
Dynamic Exercise ◽  
Significant Shift ◽  
Α Subunit ◽  
Myocardial Signal ◽  
Significant Difference

Roth, David A., Cynthia D. White, Deborah A. Podolin, and Robert S. Mazzeo. Alterations in myocardial signal transduction due to aging and chronic dynamic exercise. J. Appl. Physiol.84(1): 177–184, 1998.—Normal aging without disease leads to diminished chronotropic and inotropic responses to catecholamine stimulation, resulting in depressed cardiac function with stress. The purpose of this study was to determine molecular mechanisms for decrements in adrenergic responsiveness of the left ventricle (LV) due to aging and to study the effects of chronic dynamic exercise on signal transduction. We measured β-adrenergic receptor (β-AR) density, adenylyl cyclase (AC) activity, and G-protein content and distribution in LV from 66 male Fischer 344 rats from three age groups that were either sedentary or treadmill trained (60 min/day, 5 days/wk, 10 wk at 75% of the maximal capacity). Final ages were 7 mo (young), 15 mo (middle-age), and 25 mo (old). There was no significant difference in β-AR density among groups as a function of age or training. AC production of adenosine 3′,5′-cyclic monophosphate (cAMP) with the use of five pharmacological stimulations revealed that old sedentary myocardium had depressed basal, receptor-dependent, G-protein-dependent, and AC catalyst stimulation (30–43%) compared with hearts from young and middle-age sedentary rats. Training did not alter AC activity in either middle-age or old groups but did increase G-protein-dependent cAMP production in young myocardium (12–34%). Immunodetectable concentrations of stimulatory and inhibitory G proteins (Gs and Gi, respectively) showed 43% less total Gs with similar Gicontent in hearts from old sedentary compared with middle-age sedentary rats. When compared with young sedentary animals, Gicontent was 39 and 50% higher in middle-age sedentary and old sedentary myocardium, respectively. With age, there was a significant shift in the α-subunit of Gs distribution from cytosolic fractions of LV homogenates to membrane-bound fractions (8–12% redistribution in middle-age sedentary vs. old sedentary). The most significant training effect was a decrease in Gi content in hearts from old trained rats (23%), which resulted in values comparable with young sedentary rats and reduced the Gi/Gs ratio by 27% in old-rat LV. We report that age-associated reductions in cardiovascular β-adrenergic responsiveness correspond with alterations in postreceptor adrenergic signaling rather than with a decrease in receptor number. Chronic dynamic exercise partially attenuates these reductions through alterations in postreceptor elements of cardiac signal transduction.

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