Jérôme Lacoux

Tropane alkaloid production by hairy roots of Atropa belladonna obtained after transformation with Agrobacterium rhizogenes 15834 and Agrobacterium tumefaciens containing rol A, B, C genes only.

Atropa belladonna leaf disks were infected by a wild strain Agrobacterium rhizogenes 15834 harboring the Ri-TL-DNA and by a disarmed Agrobacterium tumefaciens strain harboring a construction with only rol ABC and npt II genes. Thirteen root lines were established and examined for their growth rate and alkaloid productivity to evaluate the possible role of rol genes in morphological differentiation and in tropane alkaloid formation. A great diversity has been observed in the growth rate of these 13 root lines. The root biomass increased up to 75 times. The total alkaloid contents were similar in the root lines obtained by infection with A. rhizogenes 15834 and A. tumefaciens rol ABC. The last ones accumulated between 4 (1.1 mg g(-1) DW) and 27 (8 mg g(-1) DW) times more alkaloids than the intact roots (0.3 mg g(-1) DW). This work has shown that the rol ABC genes were sufficient to increase tropane alkaloid production in A. belladonna hairy root cultures.

Antisense transgenesis of tobacco with a flax pectin methylesterase affects pollen ornamentation

Summary.Antisense transgenesis of tobacco (Nicotiana tabacum) with a partial flax (Linum usitatissimum L.) pectin methylesterase (Lupme3) cDNA sequence yielded plants with altered pollen content. Moreover, the characteristically sculptured cell wall surrounding the pollen grains was modified in transgenic tobacco plants: the wavy ornamentation was dramatically reduced, suggesting the involvement of the demethylation of pectin in the pollen cell wall-specific structure. Germination of pollen was decreased and the pollen tube surface aspect was also different in transgenic plants.

Antisense transgenesis of Linum usitatissimum with a pectin methylesterase cDNA

Abstract A cDNA of a flax ( Linum usitatissimum ) pectin methylesterase (PME) gene, Lupme3 , was isolated by RACE-PCR. A partial sequence of this cDNA was inserted in antisense orientation downstream the cauliflower mosaic virus 35S promoter and introduced into the flax genome via Agrobacterium tumefaciens . Transgenic calli derived from the cocultivated explants were analysed for the antisense sequence expression, and for their PME activity as well as their degree of pectin methylesterification and level of bound cations in the cell wall. Expression of the antisense sequence was correlated with a decrease of sense transcripts and a decrease of the PME enzyme activity of cell extracts at pH 8.5. In transgenic cells, a slight increase of activity was observed at acidic pH (5.5), possibly due to a compensation phenomenon and a moderately basic isoform appeared on IEF of transgenic lines. A decrease of the bound potassium level was also noted.

Activity of a flax pectin methylesterase promoter in transgenic tobacco pollen.

The regulatory region of the flax Lupme3 gene, which codes for a pectin methylesterase, contains two sequences (PB box) that are putative cis-active sequence elements thought to regulate transcription in pollen. The Lupme3 promoter was fused to the beta-glucuronidase (gus) reporter gene. The chimeric gene fusion was introduced into tobacco via Agrobacterium-mediated transformation. Expression of the reporter gene was monitored using a histochemical X-Gluc assay at different stages of pollen maturation and germination. The Lupme3 promoter was found to be active in germination-competent mature pollen and in pollen tube.

Does nitrogen fertilization history affects short-term microbial responses and chemical properties of soils submitted to different glyphosate concentrations?

The use of nitrogen (N) fertilizer and glyphosate-based herbicides is increasing worldwide, with agriculture holding the largest market share. The agronomic and socioeconomic utilities of glyphosate are well established; however, our knowledge of the potential effects of glyphosate applied in the presence or absence of long-term N fertilization on microbial functional activities and the availability of soil nutrients remains limited. Using an ex situ approach with soils that did (N+) or did not (N0) receive synthetic N fertilization for 6 years, we assessed the impact of different rates (no glyphosate, CK; field rate, FR; 100 × field rate, 100FR) of glyphosate application on biological and chemical parameters. We observed that, after immediate application (1 day), the highest dose of glyphosate (100FR) negatively affected the alkaline phosphatase (AlP) activity in soils without N fertilization history and decreased the cation exchange capacity (CEC) in N0 compared to CK and FR treatments with N+. Conversely, the 100FR application increased nitrate (NO3-) and available phosphorus (PO43-) regardless of N fertilization history. Then, after 8 and 15 days, the N+\100FR and N+\FR treatments exhibited the lowest values for dehydrogenase (DH) and AlP activities, respectively, while urease (URE) activity was mainly affected by N fertilization. After 15 days and irrespective of N fertilization history, the FR glyphosate application negatively affected the degradation of carbon substrates by microbial communities (expressed as the average well color development, AWCD). By contrast, the 100FR treatment positively affected AWCD, increasing PO43- by 5 and 16% and NO3- by 126 and 119% in the N+ and N0 treatments, respectively. In addition, the 100FR treatment resulted in an increase in the average net nitrification rate. Principal component analysis revealed that the 100FR glyphosate treatment selected microbial communities that were able to metabolize amine substrates. Overall, the lack of N fertilization in the 6 past years combined with the highest glyphosate application rate (100FR) induced the highest values of AWCD, functional diversity, NO3-, PO43- and nitrification. We concluded that the intensive use of N fertilization for 6 years may change the non-target effects of glyphosate application on enzyme activities. The functional activities, nitrification and nutrient contents were increased by glyphosate only when applied at 100 times the field application rate.

Conversion to No-Till Improves Maize Nitrogen Use Efficiency in a Continuous Cover Cropping System

A two-year experiment was conducted in the field to measure the combined impact of tilling and N fertilization on various agronomic traits related to nitrogen (N) use efficiency and to grain yield in maize cultivated in the presence of a cover crop. Four years after conversion to no-till, a significant increase in N use efficiency N harvest index, N remobilization and N remobilization efficiency was observed both under no and high N fertilization conditions. Moreover, we observed that grain yield and grain N content were higher under no-till conditions only when N fertilizers were applied. Thus, agronomic practices based on continuous no-till appear to be a promising for increasing N use efficiency in maize.