Mauch-Mani, Brigitte

2014, Planchamp, Chantal, Glauser, Gaetan, Mauch-Mani, Brigitte

2013, Planchamp, Chantal, Mauch-Mani, Brigitte

To protect themselves against biotic and abiotic stresses, plants have developed a broad range of defense mechanisms that are constitutively present or that can be induced in response to a stress. Such induced defense can be the result of a resistance elicitation by non-pathogenic organisms that are present in soil and is then called induced systemic resistance (ISR). ISR confers plant resistance against a large variety of attackers such as pathogens and herbivores. In monocotyledonous plants this phenomenon has been less studied than in dicots such as Arabidopsis. Hence, the aim of this thesis was to enhance our knowledge on ISR in monocots and more specifically in maize plants.
To facilitate plant root manipulation for our experiments, we established a soil-free system for growing maize plants. Based on an existing system for root observation, we adapted a system that is convenient for working with beneficial as well as pathogenic microbes.
ISR establishment necessitates the local recognition of the beneficial microbe by the plant. Thus, we studied the reaction of maize after inoculation with a well-known maize colonizer rhizobacterium Pseudomonas putida KT2440. The presence of these bacteria activated plant immunity early in the interaction. We hypothesized that KT2440 manipulates root defense to be able to colonize roots. We observed that KT2440 had a beneficial effect on plant growth, showing their capacity to be a plant growth promoting rhizobacteria.
After analyzing the local plant response to KT2440 inoculation we tested the efficiency of KT2440 to induce a systemic defense against various types of attacks. We demonstrated that ISR triggered by KT2440 was efficient against an hemibiotrophic fungus, Colletotrichum graminicola, and a generalist herbivore, Spodoptera littoralis. However, the efficacy of ISR induced by KT2440 was dependent of the host-plant specialization of the leaf herbivores as ISR triggered by KT2440 did not affect the specialist S. frugiperda. Our transcript and metabolite analyses revealed the involvement of phenolic compounds as well as ethylene-dependent signaling in maize ISR. However, mechanisms involved in ISR induced by KT2440 in maize remain to be further investigated.

2011, Erb, Matthias, Balmer, Yves, de Lange, Elvira S., von Merey, Georg, Planchamp, Chantal, Robert, Christelle Aurélie Maud, Röder, Gregory, Sobhy, Islam, Zwahlen, Claudia, Mauch-Mani, Brigitte, Turlings, Ted

Determining links between plant defence strategies is important to understand plant evolution and to optimize crop breeding strategies. Although several examples of synergies and trade-offs between defence traits are known for plants that are under attack by multiple organisms, few studies have attempted to measure correlations of defensive strategies using specific single attackers. Such links are hard to detect in natural populations because they are inherently confounded by the evolutionary history of different ecotypes. We therefore used a range of 20 maize inbred lines with considerable differences in resistance traits to determine if correlations exist between leaf and root resistance against pathogens and insects. Aboveground resistance against insects was positively correlated with the plant's capacity to produce volatiles in response to insect attack. Resistance to herbivores and resistance to a pathogen, on the other hand, were negatively correlated. Our results also give first insights into the intraspecific variability of root volatiles release in maize and its positive correlation with leaf volatile production. We show that the breeding history of the different genotypes (dent versus flint) has influenced several defensive parameters. Taken together, our study demonstrates the importance of genetically determined synergies and trade-offs for plant resistance against insects and pathogens.

2014, Boachon, Benoît, Gamir, Jordi, Pastor, Victoria, Erb, Matthias, Dean, John V., Flors, Victor, Mauch-Mani, Brigitte

2013, Planchamp, Chantal, Balmer, Dirk, Hund, Andreas, Mauch-Mani, Brigitte

2011, Thuerig, Barbara, Slaughter, Ana R., Marouf, Elaheh, Held, Matthias, Mauch-Mani, Brigitte, Tamm, Lucius

The influence of site on resistance of grapevine (cv. Chasselas) to Plasmopara viticola was evaluated. Grapevine leaves from three vineyards in the region of Lake Neuchâtel (Switzerland) were tested for their susceptibility to P. viticola in the lab in five successive years (2004–2008), and the expression levels of four selected defence-related genes (Glucanase, Lipoxygenase 9, 9-cis epoxycarotenoid dioxygenase, Stilbene synthase) were studied in 1 year. In all 5 years of examination, differences between sites were substantial. In four out of 5 years, plants from site Hauvernier were much less susceptible to P. viticola than plants from site Auvernier. In another year, differences were less pronounced but still significant for one leaf age. Susceptibility of plants from a third site (Concise) varied from year to year. Differences in the genetic background were excluded by microsatellite analysis. Differences in susceptibility were mirrored in the constitutive expression pattern of four defence-related genes, with samples from the Hauterive site clearly separated from samples of the other two sites in redundancy analysis. Furthermore, it was evaluated whether site-specific resistance can be modulated by agronomic practices such as the application of organic amendments. In two commercial vineyards (cv. Pinot noir), soils had either not (control) or yearly (compost) been amended with a compost for the last 9 years. Leaves from plants grown in any of the two treatments did not differ in their susceptibility to P. viticola in both years of examination. Additionally, under controlled conditions, none of 19 different composts amended to the substrate of grapevine seedlings or cuttings affected their susceptibility to P. viticola, but 8 out of 19 composts reduced severity in the control bioassay Arabidopsis thaliana—Hyaloperonospora arabidopsidis, indicating that a modulation of site-specific susceptibility of grapevine plants by organic amendments is at the very least, difficult.

2013, Balmer, Dirk, Papajewski, Daniela Villacres, Planchamp, Chantal, Glauser, Gaetan, Mauch-Mani, Brigitte

2012, Balmer, Dirk, Planchamp, Chantal, Mauch-Mani, Brigitte

2007, Ton, Jurriaan, D'Alessandro, Marco, Jourdie, Violaine, Jakab, Gabor, Karlen, Danielle, Held, Matthias, Mauch-Mani, Brigitte, Turlings, Ted

Plants counteract attack by herbivorous insects using a variety of inducible defence mechanisms. The production of toxic proteins and metabolites that instantly affect the herbivore's development are examples of direct induced defence. In addition, plants may release mixtures of volatile organic compounds (VOCs) that indirectly protect the plant by attracting natural enemies of the herbivore. Recent studies suggest that these VOCs can also prime nearby plants for enhanced induction of defence upon future insect attack. However, evidence that this defence priming causes reduced vulnerability to insects is sparse. Here we present molecular, chemical and behavioural evidence that VOC-induced priming leads to improved direct and indirect resistance in maize. A differential hybridization screen for inducible genes upon attack by Spodoptera littoralis caterpillars identified 10 defence-related genes that are responsive to wounding, jasmonic acid (JA), or caterpillar regurgitant. Exposure to VOCs from caterpillar-infested plants did not activate these genes directly, but primed a subset of them for earlier and/or stronger induction upon subsequent defence elicitation. This priming for defence-related gene expression correlated with reduced caterpillar feeding and development. Furthermore, exposure to caterpillar-induced VOCs primed for enhanced emissions of aromatic and terpenoid compounds. At the peak of this VOC emission, primed plants were significantly more attractive to parasitic Cotesia marginiventris wasps. This study shows that VOC-induced priming targets a specific subset of JA-inducible genes, and links these responses at the molecular level to enhanced levels of direct and indirect resistance against insect attack.