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Reims, France

Colin F.,French National Institute for Agricultural Research | Ducousso A.,French National Institute for Agricultural Research | Fontaine F.,Laboratoire Of Stress
Annals of Forest Science | Year: 2010

• The provenance effect on epicormics is poorly documented and restricted to epicormic shoots. Our objective was to characterize the relationship between epicormics and provenance on 13-year-old Quercus petraea trees, taking into account their growth traits. • On the growth units (GU) studied, epicormics were essentially isolated buds (95%) and they were mainly located at branch bases, secondarily on GU limits and marginally on lateral position. Provenance effect was very small on the number of epicormics and slightly larger on the number of branches and GU limits. On the contrary, the growth situation -independently from provenance- proved to have a larger effect on the 2 latter growth traits. • Altogether, these results clearly show the predominant effect of morphological traits and thus of ontogeny. This opens important research perspectives: how growth conditions and genetics (at progeny and individual levels) influence height growth, setting and fate of axillary buds on the one hand and fate of epicormic buds inserted directly on the stem, or at branch bases on the other hand. © INRA, EDP Sciences, 2010.

Colin F.,French National Institute for Agricultural Research | Mothe F.,French National Institute for Agricultural Research | Freyburger C.,French National Institute for Agricultural Research | Morisset J.-B.,French National Institute for Agricultural Research | And 2 more authors.
Trees - Structure and Function | Year: 2010

Branch knots and other traces of lateral axes, known as rameal traces, have generally been disregarded within architectural studies based on external observations and their analysis limited to tedious manual dissection methods. Based on non-destructive methods including X-ray CT scanning (XRCTS) and on the ontogenic knowledge progressively accumulated on Quercus petraea, this paper presents (1) the tracking methodology of all rameal traces with XRCTS and the "Gourmands" plugin, and software created downstream, notably the 3D visualisation software "Bil3D"; (2) preliminary results obtained on two Quercus petraea 50 cm-long logs; and (3) potential applications in the fields of biology and ecology. Of approximately 45 sequences of linked rameal traces (composing rameal sequences) per metre, half were directly connected to the pith as horizontal traces of primary epicormic buds, while the other half were connected to a branch by an oblique knot. Horizontal epicormic knots essentially emerged within the tree from the most intensive thinning treatment and led to additional knots in the clear wood. Secondary epicormic shoots may emerge from branch and epicormic knots, leading to a vertical spread of epicormic sites for the former and to more bud clusters for the latter. Engulfment of lateral axes can be quantified. Assumptions on the origin of between-tree variability are proposed. Our methodology opens the way to an exhaustive description of rameal traces. It is relevant for ontogenic and wood quality assessment at the trunk level. It may also be very useful for characterising the potentiality of reiteration and for repairing shoot damage and vegetative regeneration at the crown, collar and even root system level. © 2010 Springer-Verlag.

Gamm M.,University of Burgundy | Heloir M.-C.,University of Burgundy | Bligny R.,CEA Grenoble | Vaillant-Gaveau N.,Laboratoire Of Stress | And 7 more authors.
Molecular Plant-Microbe Interactions | Year: 2011

The oomycete Plasmopara viticola is responsible for downy mildew, a severe grapevine disease. In infected grapevine leaves, we have observed an abnormal starch accumulation at the end of the dark period, suggesting modifications in starch metabolism. Therefore, several complementary approaches, including transcriptomic analyses, measurements of enzyme activities, and sugar quantification, were performed in order to investigate and to understand the effects of P. viticola infection on leaf starch and-to a larger extent-carbohydrate metabolism. Our results indicate that starch accumulation is associated with an increase in ADP-glucose pyrophosphorylase (AGPase) activity and modifications in the starch degradation pathway, especially an increased α-amylase activity. Together with these alterations in starch metabolism, we have observed an accumulation of hexoses, an increase in invertase activity, and a reduction of photosynthesis, indicating a source-to-sink transition in infected leaf tissue. Additionally, we have measured an accumulation of the disaccharide trehalose correlated to an increased trehalase gene expression and enzyme activity. Altogether, these results highlight a dramatic alteration of carbohydrate metabolism correlated with later stages of P. viticola development in leaves. © 2011 The American Phytopathological Society.

Sanchez L.,Laboratoire Of Stress | Courteaux B.,Laboratoire Of Stress | Hubert J.,CNRS Institute of Molecular Chemistry - Reims | Kauffmann S.,University of Reims Champagne Ardenne | And 5 more authors.
Plant Physiology | Year: 2012

Plant resistance to phytopathogenic microorganisms mainly relies on the activation of an innate immune response usually launched after recognition by the plant cells of microbe-associated molecular patterns. The plant hormones, salicylic acid (SA), jasmonic acid, and ethylene have emerged as key players in the signaling networks involved in plant immunity. Rhamnolipids (RLs) are glycolipids produced by bacteria and are involved in surface motility and biofilm development. Here we report that RLs trigger an immune response in Arabidopsis (Arabidopsis thaliana) characterized by signaling molecules accumulation and defense gene activation. This immune response participates to resistance against the hemibiotrophic bacterium Pseudomonas syringae pv tomato, the biotrophic oomycete Hyaloperonospora arabidopsidis, and the necrotrophic fungus Botrytis cinerea. We show that RL-mediated resistance involves different signaling pathways that depend on the type of pathogen. Ethylene is involved in RL-induced resistance to H. arabidopsidis and to P. syringae pv tomato whereas jasmonic acid is essential for the resistance to B. cinerea. SA participates to the restriction of all pathogens. We also show evidence that SA-dependent plant defenses are potentiated by RLs following challenge by B. cinerea or P. syringae pv tomato. These results highlight a central role for SA in RL-mediated resistance. In addition to the activation of plant defense responses, antimicrobial properties of RLs are thought to participate in the protection against the fungus and the oomycete. Our data highlight the intricate mechanisms involved in plant protection triggered by a new type of molecule that can be perceived by plant cells and that can also act directly onto pathogens. © 2012 American Society of Plant Biologists.

Letousey P.,Laboratoire Of Stress | Baillieul F.,Laboratoire Of Stress | Perrot G.,Laboratoire Of Stress | Rabenoelina F.,Laboratoire Of Stress | And 4 more authors.
Phytopathology | Year: 2010

Plant infection by pathogens generates various forms of symptoms. Most of them have been described as soon as they become visible, whereas preceding, discrete signs during incubation are poorly or not understood. In Vitis vinifera, esca-related pathogenic fungi inhabit living trunk wood and induce the so-called apoplexy, a sudden wilting of leaves within a few days. To further understand the apoplexy expression, the period preceding symptom appearance was investigated by following physiological and molecular markers associated with photosynthetic mechanisms and stress responses. Within the week preceding symptoms, drastic physiological alterations of photosynthesis were registered in pre-apoplectic vines, as revealed by a decrease in gas exchange, changes in chlorophyll fluorescence, and repression of photosynthesis-related genes. In the meantime, expression of defense-related genes was induced and amplified during symptom expression. Water-stress-related genes were specifically investigated because water transport may be impeded by clogging xylem vessels due to esca-causing fungi. Neither of the tested water-stress-related genes was affected in pre-apoplectic grapevine leaves whereas these genes were downregulated in drying leaves. Our results suggest that, during incubation of esca apoplexy, grapevine perceives some signals (likely fungi-originated toxins) and reacts by reducing photosynthesis and triggering defense mechanisms.

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