The largest reservoir of mitochondrial introns is a relic of an ancestral split gene

In eukaryotes, introns are located in nuclear and organelle genes from several kingdoms (ref. 1-4). Large introns (0.1 to 5 kbp) are frequent in mitochondrial genomes of plant and fungi (ref. 1,5) but scarce in Metazoa, despite these organisms are grouped with fungi among Opisthokonts. Introns are classified in two main groups (I and II) according to their RNA secondary structure involved in the intron self-splicing mechanism (ref. 5,6). Most of the group I introns carry a "Homing Endonuclease Gene" (ref. 7-9) encoding a DNA endonuclease acting in the transfer and site specific integration "homing") and allowing the intron spreading and gain after lateral transfer even between species from different kingdoms (ref. 10,11). Opposite to this "late intron" paradigm, the "early intron" theory indicates that introns, which would have been abundant in the ancestral genes, would mainly evolve by loss (ref. 12,13).

Here we report the sequence of the cox1 gene of the button mushroom _Agaricus bisporus_, the most worldwide cultivated mushroom. This gene is both the longest mitochondrial gene (29,902 nt) and the largest Group I intron reservoir reported to date. An analysis of the group I introns available in _cox1_ genes shows that they are ancestral mobile genetic elements, whose frequent events of loss (according to the "late theory") and gain by lateral transfer ("early theory") must be combined to explain their wide and patchy distribution extending on several kingdoms. This allows the conciliation of the "early" and "late intron" paradigms, which are still matters of much debate (ref. 14,15). The overview of the intron distribution indicates that they evolve towards elimination. In such a landscape of eroded and lost intron sequences, the _A. bisporus_ largest intron reservoir, by its singular dynamics of intron keeping and catching, constitutes the most fitted relic of an early split gene

The Agaricus bisporus cox1 Gene: The Longest Mitochondrial Gene and the Largest Reservoir of Mitochondrial Group I Introns

In eukaryotes, introns are located in nuclear and organelle genes from several kingdoms. Large introns (up to 5 kbp) are frequent in mitochondrial genomes of plant and fungi but scarce in Metazoa, even if these organisms are grouped with fungi among the Opisthokonts. Mitochondrial introns are classified in two groups (I and II) according to their RNA secondary structure involved in the intron self-splicing mechanism. Most of these mitochondrial group I introns carry a “Homing Endonuclease Gene” (heg) encoding a DNA endonuclease acting in transfer and site-specific integration (“homing”) and allowing intron spreading and gain after lateral transfer even between species from different kingdoms. Opposed to this gain mechanism, is another which implies that introns, which would have been abundant in the ancestral genes, would mainly evolve by loss. The importance of both mechanisms (loss and gain) is matter of debate. Here we report the sequence of the cox1 gene of the button mushroom Agaricus bisporus, the most widely cultivated mushroom in the world. This gene is both the longest mitochondrial gene (29,902 nt) and the largest group I intron reservoir reported to date with 18 group I and 1 group II. An exhaustive analysis of the group I introns available in cox1 genes shows that they are mobile genetic elements whose numerous events of loss and gain by lateral transfer combine to explain their wide and patchy distribution extending over several kingdoms. An overview of intron distribution, together with the high frequency of eroded heg, suggests that they are evolving towards loss. In this landscape of eroded and lost intron sequences, the A. bisporus cox1 gene exhibits a peculiar dynamics of intron keeping and catching, leading to the largest collection of mitochondrial group I introns reported to date in a Eukaryote

CYTOTOXICITY STUDY OF ANTIDIABETIC PLANTS ON NEUROBLASTOMA CELLS CULTURED AT NORMAL AND HIGH GLUCOSE LEVEL

Objective:In diabetes, chronic hyperglycemia causes damage (glucose toxicity) on some cells leading to micro and macro vascular complications. The aim of this study was to investigate the effect of antidiabetic plants extracts in high glucose concentration in vitro. Methods: Phyllanthus amarus (whole plant), Vitex doniana (leaves), Tectona grandis (leaves and trunk bark) and Plumeria alba (roots) hydroalcoholic extract (at the concentrations of 6.25, 25, 75, 125, 250 and 500 µg/ml) were tested for their possible cytotoxicity using the 3-(4,5-dimetylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay on neuroblastoma cells lines in standard condition (extract alone) and high glucose concentration (extract+50 mM glucose). Results: At concentrations of 6.25 and 25µg/ml, T. grandis bark and leaves and P. amarus induced a significant decrease (p<0.01; p<0.001) on cell viability as compared to controls. The decrease on cell viability was very pronounced in the presence of the extracts plus glucose 50 mM. P. amarus extract becomes increasingly toxic as the concentration of extract increased in the presence of glucose. With P. amarus at 125 µg/ml and glucose at 50 mM, there is no more viable cells in the medium. By contrast, T. grandis bark extract induced a significant reduction of the cytotoxicity in the presence of glucose compared to standard condition. Conclusion:It appears that, only hydroalcoholic extract of T. grandis bark possesses neuroprotective activity in high glucose concentration

Characterization and expression of the cDNA encoding a new kind of phospholipid transfer protein, the phosphatidylglycerol/phosphatidylinositol transfer protein from Aspergillus oryzae : evidence of a putative membrane targeted phospholipid transfer protein in fungi

International audienc

Idiophasic metabolism shift localization at mycelial and hyphal levels case of mycotoxin biosyntheses and secretion

National audienc

Characterization and expression of the cDNA encoding a new kind of phospholipid transfer protein, the phosphatidylglycerol/phosphatidylinositol transfer protein from Aspergillus oryzae : evidence of a putative membrane targeted phospholipid transfer protein in fungi

International audienc

Leveraging Idiophasic metabolism shift localization at mycelial and hyphal levels: case of mycotoxin biosynthesis and secretion

National audienc

Cloning and expression in phospholipid containing cultures of the gene encoding the specific phosphatidylglycerol/phosphatidylinositol transfer protein from Aspergillus oryzae : evidence that the pg/pi-tp is tandemly arranged with the putative 3-ketoacyl-CoA thiolase gene

International audienc

Safety evaluation of Agaricus subrufescens varieties and their products of therarpeutic interest or for disease prevention

National audienceMushrooms are food traditionally consumed in Europe, Asia and America. They are being studied for medicinal benefits. Extensive studies have shown that Agaricus subrufescens ( A. blazei Murrill or A. brasiliensis) has anticancer properties. A comparative study of Agaricus subrufescens strains (from Brazil and France) is presented herein using Agaricus bisporus (champignon de Paris) as control. In vivo OCDE test were performed to evaluate either tolerance and/or acute and sub chronic toxicity in rats and mice. Our data reveal that all A. subrufescens strains are not toxic, either in vivo or in vitro, except some locomotor hypoactivity. All show a preventing effect against carcinogenesis, including A. bisporus. This is the first time that this mushroom is shown to be effective, even thought it is clearly less effective than A. subrufescens. However no anti tumour effect is found using Balb-c mice implanted with leukaemia cells. Furthermore they elicit slight cell growth stimulation at the concentrations tested in vitro, in Hep G2 (human hepatoma cells) and Neuro 2a (mouse neuroblastoma cells). The most active is A. subrufescens from Brazil. These mushrooms do have many bioactive compounds, different from the polysaccharides that need to be isolated and characterised for their curative properties following accurate evaluation of toxicological effects. Indeed there is clearly a lake of information on toxicological assessment (acute and chronic toxicity) of compound such as agaritine, blazein among others and of the whole mushroom A. subrufescens itself, and overall on epidemiological data linking the consumption of Agaricus sp and eventual prevention and/or pathologies