書評論文

Effect of chilling on gene expression in the leaves of two maize hybrids. The 7-day chilling treatment (10 °C day/4 °C night) was applied at about the 6-VL stage. Analyses were performed at the end of the chilling treatment for treated plants or 1 day after the beginning of the treatment for control plants in order to compare plants at the same developmental stage. a and b are biological replicates of Fig. 6. Data are means ± se of 3 technical replicates. Gene abbreviations: ICE1 (INDUCER OF CBF/DREB EXPRESSION 1), DREB1 (DROUGHT-RESPONSIVE ELEMENT BINDING), CDKA1 (CYCLIN DEPENDENT KINASE A 1), CYCA3 (CYCLIN A 3), KRP1 (CYCLIN-DEPENDENT KINASE INHIBITOR 1), EXPA4 (ALPHA EXPANSIN 4), EXPB2 (BETA EXPANSIN 2), GGR (GERANYLGERANYL REDUCTASE), CAB1 (CHLOROPHYLL A/B BINDING PROTEIN), psbS (CP22 PSII subunit), VDE (VIOLAXANTHIN DE-EPOXIDASE), PEPC (PHOSPHOENOLPYRUVATE CARBOXYLASE), PPDK (PYRUVATE, ORTHOPHOSPHATE DIKINASE) and rbcS (RUBISCO small subunit). (PDF 351 kb

Recherche de GTLs et choix de cibles stratégiques pour l'amélioration de la tolérance aux basses températures chez le maïs

La tolérance au froid est un caractère complexe lié à des modifications au niveau écophysiologique et métabolique. L'objectif de ce travail est d'identifier les zones chromosomiques clés impliquées dans la tolérance aux basses températures à partir d'une étude sur une population de backcross avancé obtenue à partir d'un parent tropical d'altitude dans le fond génétique d'un parent corné. Une approche sans a priori repose sur la mise en évidence des zones chromosomiques impliquées dans les variations de biomasse en réponse au froid ainsi que sur les origines de ces variations: mise en place des feuilles, photosynthèse et métabolismes carboné et azoté. Une approche avec a priori est basée sur l'hypothèse que le glutathion, molécule antioxydante, serait une molécule clé dans la tolérance aux basses températures. Grâce à ces deux approches, nous concluons que la photosynthèse semble jouer un rôle primordial mais que le rôle du glutathion reste limité dans notre contexte génétique et pour les scénarios climatiques testés.Cold tolerance is a complex mechanism linked to ecophysiological and physiological changes. The aim of this work was to identify key chromosomal regions involved in low temperature tolerance. This work was based on a population resulting from the advanced back-cross with a highland tropical inbred within a flint background. A first approach was based on the detection of chromosomal regions involved in biomass changes in response to cold and their origin: canopy development, photosynthesis, carbon and nitrogen metabolisms. A second approach was based on the hypothesis that an antioxidant, the glutathione, bas a key role in low temperature tolerance. Combining these two approaches, we conclude that photosynthesis seems to play a key rote when the glutathione one is limited in our genetic background and for the climatic conditions tested.COMPIEGNE-BU (601592101) / SudocSudocFranceF

Maize plants can enter a standby mode to cope with chilling stress

Background European Flint maize inbred lines are used as a source of adaptation to cold in most breeding programs in Northern Europe. A deep understanding of their adaptation strategy could thus provide valuable clues for further improvement, which is required in the current context of climate change. We therefore compared six inbreds and two derived Flint x Dent hybrids for their response to one-week at low temperature (10°C day/7 or 4°C night) during steady-state vegetative growth. Results Leaf growth was arrested during chilling treatment but recovered fast upon return to warm temperature, so that no negative effect on shoot biomass was measured. Gene expression analyses of the emerging leaf in the hybrids suggest that plants maintained a ‘ready-to-grow’ state during chilling since cell cycle genes were not differentially expressed in the division zone and genes coding for expansins were on the opposite up-regulated in the elongation zone. In photosynthetic tissues, a strong reduction in PSII efficiency was measured. Chilling repressed chlorophyll biosynthesis; we detected accumulation of the precursor geranylgeranyl chlorophyll a and down-regulation of GERANYLGERANYL REDUCTASE (GGR) in mature leaf tissues. Excess light energy was mostly dissipated through fluorescence and constitutive thermal dissipation processes, rather than by light-regulated thermal dissipation. Consistently, only weak clues of xanthophyll cycle activation were found. CO2 assimilation was reduced by chilling, as well as the expression levels of genes encoding phosphoenolpyruvate carboxylase (PEPC), pyruvate orthophosphate dikinase (PPDK), and the small subunit of Rubisco. Accumulation of sugars was correlated with a strong decrease of the specific leaf area (SLA). Conclusions Altogether, our study reveals good tolerance of the photosynthetic machinery of Northern European maize to chilling and suggests that growth arrest might be their strategy for fast recovery after a mild stress.Thermomaï

Genetic variation for heterotrophic growth in maize in relation to temperature

The investigation was conducted in the frame of early maize (Zea mays L) adaptation to northern Europe climatic conditions. In these countries, tolerance to low temperature during the first stages of development is necessary to ensure a good yield. We were therefore interested in seedling behaviour during heterotrophic growth. We observed rates of radicle elongation of 13 genotypes (inbred lines, hybrids or populations) at 18 controlled temperatures from 6 to 40 °C. One group of genotypes was used to determine endosperm influence. Results of non-linear analysis were in favour of the existence of genetic variation, even if seed effects were not clearly determined. This variation was found to be due to differences in temperature sensitivity or seedling vigour. It was particularly evident for elongation rates (from 0 to 0.2 mm/s in a cold environment, and for optimum temperature between 27 and 30 °C).Cette étude se situe dans le cadre de l’adaptation des maïs (Zea mays L) précoces aux conditions climatiques du Nord de l’Europe. Dans ces régions, la tolérance aux basses températures pendant les premiers stades de développement est nécessaire pour assurer un bon rendement. Nous nous sommes intéressés au comportement de plantules pendant la phase de croissance hétérotrophe. Nous avons observé la vitesse d’élongation de la radicule de 13 génotypes (lignées, hybrides ou populations) à 18 températures comprises entre 6 et 40 °C (fig 4). Un groupe de génotypes a permis d’étudier l’influence de la qualité de la semence. Les résultats de l’analyse non linéaire permettent de conclure à l’existence d’une variabilité génétique, même si l’effet du support-semence n’a pas pu être précisément défini. Cette variabilité trouve son origine dans des différences de sensibilité aux températures ou dans des différences de niveaux de vigueur. Elle se traduit en particulier par des variations de la vitesse de croissance à basse température entre 0 et 0,2 mm/s (tableau III) ou des déplacements de l’optimum thermique entre 27 et 30 °C (tableau II)

Heterosis in maize for biomass production, leaf area establishment, and radiation use efficiency under cool spring conditions

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Eléments de l'organisation fonctionnelle des végétaux

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Maize plants can enter a standby mode to cope with chilling stress

Background: European Flint maize inbred lines are used as a source of adaptation to cold in most breeding programs in Northern Europe. A deep understanding of their adaptation strategy could thus provide valuable clues for further improvement, which is required in the current context of climate change. We therefore compared six inbreds and two derived Flint x Dent hybrids for their response to one-week at low temperature (10 degrees C day/7 or 4 degrees C night) during steady-state vegetative growth. [br/] Results: Leaf growth was arrested during chilling treatment but recovered fast upon return to warm temperature, so that no negative effect on shoot biomass was measured. Gene expression analyses of the emerging leaf in the hybrids suggest that plants maintained a 'ready-to-grow' state during chilling since cell cycle genes were not differentially expressed in the division zone and genes coding for expansins were on the opposite up-regulated in the elongation zone. In photosynthetic tissues, a strong reduction in PSII efficiency was measured. Chilling repressed chlorophyll biosynthesis; we detected accumulation of the precursor geranylgeranyl chlorophyll a and down-regulation of GERANYLGERANYL REDUCTASE (GGR) in mature leaf tissues. Excess light energy was mostly dissipated through fluorescence and constitutive thermal dissipation processes, rather than by light-regulated thermal dissipation. Consistently, only weak clues of xanthophyll cycle activation were found. CO2 assimilation was reduced by chilling, as well as the expression levels of genes encoding phosphoenolpyruvate carboxylase (PEPC), pyruvate orthophosphate dikinase (PPDK), and the small subunit of Rubisco. Accumulation of sugars was correlated with a strong decrease of the specific leaf area (SLA). [br/] Conclusions: Altogether, our study reveals good tolerance of the photosynthetic machinery of Northern European maize to chilling and suggests that growth arrest might be their strategy for fast recovery after a mild stress

Conversion of intercepted radiation into aerial dry biomass for three maize genotypes : influence of plant density

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Effet de la duree du jour sur la mise en place de la surface foliaire chez le mais

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