Implication des méthionines sulfoxide réductases dans la longévité des graines

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Patterns of protein carbonylation during Medicago truncatula seed maturation

Seeds mainly acquire their physiological quality during maturation, whereas oxidative conditions reign within cells triggering protein carbonylation. To better understand the role of this protein modification in legume seeds, we compared by proteomics patterns of carbonylated proteins in maturing seeds of Medicago truncatula naturally desiccated or prematurely dried, a treatment known to impair seed quality acquisition. In both cases, protein carbonylation increased in these seeds, accompanying water removal. We identified several proteins whose extent of carbonylation varied when comparing natural desiccation and premature drying and that could therefore be responsible for the impairment of seed quality acquisition or expression. In particular, we focused on PM34, a protein specific to seeds exhibiting a high sensitivity to carbonylation and of which function in dicotyledons was not known before. PM34 proved to have a cellulase activity presumably associated with cell elongation, a process required for germination and subsequent seedling growth. We discuss the possibility that PM34 (abundance or redox state) could be used to assess crop seed quality

A Photoacoustic Study of Xenon Implantation in CuInSe2CuInSe_2

In this paper, we report a study on the optical properties of xenon ion implanted $CuInSe_2$ single crystals using a high resolution near-infrared photoacoustic spectrometer of the gas-microphone type. Samples of high quality of $CuInSe_2$, p-type conducting, have been implanted with $Xe^{+}$ at 40 keV with doses of $5 \times 10^{15},$ $10^{16}$ and $5 \times 10^{16}$ ions/$cm^2$. Photoacoustic spectra have been measured before and after implantation. A newly developed theoretical model based on a two-layer sample configuration has been used to single out the spectral dependence of the absorption coefficient of the implanted layer from that of the substrate. The absorption spectra were used to evaluate the gap energy and to establish ionization energies for several shallow and deep defect states. The resulting effects following the introduction of xenon into $CuInSe_2$ at different doses are discussed in the light of published literature