Serotonin is a well known neurotransmitter in mammals and plays an important role in various mental functions in humans. In plants, the serotonin biosynthesis pathway and its function are not well understood. The rice sekiguchi lesion (sl) mutants accumulate tryptamine, a candidate substrate for serotonin biosynthesis. We isolated the SL gene by map-based cloning and found that it encodes CYP71P1 in a cytochrome P450 monooxygenase family. A recombinant SL protein exhibited tryptamine 5-hydroxylase enzyme activity and catalyzed the conversion of tryptamine to serotonin. This pathway is novel and has not been reported in mammals. Expression of SL was induced by the N-acetylchitooligosaccharide (chitin) elicitor and by infection with Magnaporthe grisea, a causal agent for rice blast disease. Exogenously applied serotonin induced defense gene expression and cell death in rice suspension cultures and increased resistance to rice blast infection in plants. We also found that serotonin-induced defense gene expression is mediated by the RacGTPase pathway and by the G␣ subunit of the heterotrimeric G protein. These results suggest that serotonin plays an important role in rice innate immunity.

Addendum to: Maisonneuve S, Bessoule J-J, Lessire R, Delseny M, Roscoe TJ. Expression of rapeseed microsomal lysophosphatidic acid acyltransferase isozymes enhances seed oil content in Arabidopsis.

We previously described the effects of intake of dairy products on plasmid dissemination in the digestive tract of gnotobiotic mice associated with human faecal flora (HFF) and found that yoghurt, heat-treated yoghurt (HTY) and milk reduced population levels of transconjugants compared with findings in mice fed a standard mouse diet. In the case of lactose intake, transconjugants were not detected. The aim of the present study was to assess the possible interrelationships between these observations and other variables (bacterial ecology, pH, moisture, enzyme activities, short-chain fatty acid (SCFA) contents, lactic acid contents). Much of the interest of the present comparison lies in the fact that the animals were homogeneous in terms of age, gender, food and intestinal microflora, owing to the gnotobiotic mouse model maintained in sterile isolators. We observed no variation in SCFA and lactic acid contents or in the population levels of strictly anaerobic strains of Bacteroides and Bifidobacterium, and of the facultative anaerobic recipient Escherichia coli PG1 strain. The main modifications were the reduction of population levels of transconjugants in mice receiving yoghurt, HTY and milk, and concomitantly an increase of b-galactosidase and a decrease of b-glucosidase activities, compared with control mice fed a standard diet. Total inhibition of plasmid transfer was observed in HFF mice consuming lactose, and concomitantly the two enzyme activities (b-glucosidase and b-galactosidase) were increased, compared with the findings in control mice fed a standard diet. In axenic mice consuming lactose, plasmid transfer occurred, b-galactosidase was not detected and b-glucosidase was decreased. It is therefore proposed that these two enzyme activities influence plasmid transfer and persistence of transconjugants in the digestive tract of HFF associated mice. When both activities were increased there was a total inhibition of plasmid transfer (case of lactose intake). When b-galactosidase increased and b-glucosidase decreased (case of yoghurt, HTY and milk), plasmid transfer occurred at a lower efficiency than in the control group, resulting in lower population levels of transconjugants.

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Résumé : Les manipulations sur la qualité de l'huile chez les plantes cultivées sont d'un intérêt majeur et dépendent des modifications de la composition en huile des graines. Les acides gras habituels sont stockés sous forme de triacylglycérols. De nombreuses espèces accumulent des acides gras inhabituels (AGI) qui peuvent servir comme précurseurs à de nombreux produits chimiques ou encore conférer de nouvelles propriétés physiques ou chimiques aux huiles. L'isolement de gènes contrôlant la synthèse d'AGI a permis la biosynthèse d'AGI par génie métabolique dans des graines de plantes cultivées. Nous présentons, ici quelques exemples de modifications de la composition en TAG chez le colza et tentons de comprendre quels peuvent être les facteurs limitant l'accumulation des AGI. Nous concluons que pour produire une huile homogène à un taux élevé, avec une nouvelle composition en acide gras chez une plante cultivée, il sera nécessaire de fournir un environnement optimal au transgène, de s'assurer que la plante est capable d'incorporer des AGI au niveau des TAG et enfin, de contrôler le métabolisme des lipides de stockage dans les graines en cours de développement chez ces plantes transgéniques.Mots-clés : acides gras inhabituels, triacylglycérols, ségrégation, Brassica napus.Summary : Vegetable-derived oils are of interest for industrial applications partly because of the chemical similarity of plant oils to mineral oils but also because of the economic need to reduce overproduction of seed oils for nutritional use. Complex oils can be produced in seeds as a low cost agricultural product based on renewable solar energy that requires less refining and is biodegradable and thus produces less adverse effects on the environment. In addition, biotechnologies have accelerated selection programmes and increased the genetic diversity available for the development of new varieties of oilseeds with specific fatty acid compositions. In the developing oilseed, energy and carbon are stored as lipid under the form of triacylglycerol, that is, a glycerol molecule to which three fatty acids are esterified. Fatty acids comprise a linear chain of carbon atoms, the first of which carries an organic acid group. The chain length and the presence of double bonds determine the properties of the fatty acid which in turn determine the physical and chemical properties of the oil of storage lipids and hence their economic value. In addition to the common C16-and C18-saturated and unsaturated fatty acids of membrane lipids, the seed storage lipids of many plant species contain unusual fatty acids (UFAs) which can vary in chain length, in the degree of unsaturation, possess double bonds in unusual positions, or can contain additional functional groups such as hydroxy, Article disponible sur le site http://www.ocl-journal.org ou http://dx

This study deals with the effects of yoghurt intake on wild-type and recombinant plasmid transfer from an exogenous Escherichia coli K12-derivative donor strain to an endogenous recipient strain in the digestive tract of mice associated with human faecal flora. We showed that the self-transmissible plasmid R388 was efficiently transferred to recipient strain PG1 in mice associated with human faecal flora (HFF-PG1) and that the resulting transconjugants (PG1-R388) became established at a high and maximal population level without any selective pressure. Using HFF-PG1 mice made it possible to determine whether yoghurt consumption decreases R388 transfer efficiency and the ability of transconjugant PG1-R388 to successfully colonise the digestive tract. Results indicated that yoghurt consumption had two effects: it reduced the efficacy of plasmid transfer 10-fold and decreased the transconjugant PG1-R388 population density 100-fold, compared to the control group. We also describe another HFF mouse model in which recipient PG1 was replaced by EM0 with which no plasmid transfer was observed. This model made it possible to demonstrate the potential promoting effect of yoghurt intake on transconjugant formation and establishment. Our results indicated no yoghurt effect; no transconjugants appeared in the digestive tract of HFF-EM0 mice fed on yoghurt or on standard food. In both mouse models, HFF-PG1 and HFF-EM0, yoghurt intake did not promote the mobilisation of either the non-self-transmissible plasmid pUB2380 or the recombinant plasmid pCE325.

Plasmid transfer occurs in the digestive tract and the transconjugants may become durably established. The aim of the present work is to investigate the effect of probiotics of plasmid transfer and on establishment of transconjugants in the gut. Plasmid transfers were carried out in the digestive tract of germ free mice associated with an E. coli K12 donor strain harboring three plasmids (R388, self-transmissible, pCE325 and pUB2380, mobilisable,) and an E. coli recipient strain, PG1, of human origin (Duval-Iflah et al., 1994). Milks fermented with either Lactobacillus bulgaricus or Streptococcus thermophilus or symbiosis, S85, of both strains were given daily as 1/3 of food diet. Fermented milks have no effect on the transfer of R388 and pUB2380 except a slight increase of TC(R388) with milk fermented with S85. Long term ingestion of milk fermented with S85 inhibited the formation and the establishment of transconjugants TC(pCE325). Milk fermented with L. bulgaricus lowered the population density of TC(pCE325) in animals where they were already established. This phenomenon was reversible, since the density of TC(pCE325) increased in the same animals after cessation of supplementation. Bacterial cultures obtained in MRS broth and given in state of drinking water were compared with fermented milks. Bacterial cultures with L. bulgaricus and with S85 favoured the establishment of TC(pCE325). There results indicate for the first time that probiotics have various effects on the formation and/or establishment of transconjugants in the gut of axenic mice. The effects depend on whether the probiotics were cultivated in milk or in MRS, indicating that bacterial metabolites and viable bacteria can be involved.

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