Résultat de la recherche
BABA in priming tomato for enhanced tolerance to drought, salinity and fungal stress and combinations thereof
La tomate compte parmi les légumes-fruits les plus importants sur le plan économique dans plusieurs pays. Cependant la sécheresse, la salinité et le les pathogènes constituent les principales causes de réduction et de variabilité des rendements des cultures. Bien que les plantes aient développé des capacités défensives contre ces stress, leur tolérance et résistance dépend du degré et de l’intensité du stress et aussi de l’espèce. Dans cette thèse, nous avons étudié le rôle de l’acide β-aminobutyrique (BABA) dans l’induction de la résistance contre le stress hydrique, le stress salin et la combinaison de salinité et infection avec Botrytis cinerea chez deux cultivars de tomate (cv Marmande : un cultivar résistant au stress et cv Cœur de Bœuf : un cultivar sensible au stress). Nos résultats ont montré que BABA atténue considérablement les effets nocifs d’un seul stress et aussi des stress combinés. Les plants de tomate sous contrainte hydrique ou saline, traités avec BABA accumulent plus de chlorophylle a et b, anthocyanine, ABA et montrent aussi une induction des gènes reliés au stress abiotique comparé aux plants non-traités. Nous avons trouvé une réduction des espèces réactives d’oxygène qui sont liées à une augmentation des antioxydants plus importante chez les plants traités avec BABA par rapport aux plants non-traités. Ce qui nous a surpris c’est que BABA induit plus de tolérance au cv Marmande qu’au cv Cœur de Bœuf. De plus, les plants traités avec BABA présentent une meilleure résistance contre la combinaison des deux stress par rapport aux plants non-traités suite à l’induction de l’accumulation de callose, d’H2O2, d’ABA, de SA et aussi l’expression de PR1 et PR5. Ceci ouvre de nombreuses perspectives quant à l’effet de BABA sur les métabolites., Tomatoes are among the most produced and consumed vegetable-fruit in many countries and is considered an economically important crop. However, drought, salinity and pathogen infection are the main causes of crop yield reduction and variability. Although plants have developed defensive capacities against these stresses, but plant tolerance and resistance depend on the degree and intensity of stress and on the species. In this thesis, we investigated the role of β-aminobutyric acid (BABA) in the induction of tolerance and resistance against drought stress, salt stress and combination of salinity and infection with Botrytis cinerea in two tomato cultivars (cv Marmande: a stress-resistant cultivar and cv Coeur de Boeuf: a stress-sensitive cultivar). Our results showed that BABA significantly reduces the harmful effects of a single and combined stress. Treated tomato plants with BABA in response to drought or salt stress accumulate more chlorophyll a and b, anthocyanin, ABA and genes related to abiotic stress compared to non-treated plants. We found a reduction in reactive oxygen species that are related to greater increase of antioxidant in treated-plants with BABA compared to non-treated ones. What surprised us is that BABA induces more tolerance to Marmande than to Coeur de Boeuf. In addition, plants treated with BABA show better resistance against the combination of both stresses compared to non-treated plants by induction of callose accumulation, H2O2, ABA, SA and the expression of PR1 and PR5. This opens many perspectives on the effect of BABA on metabolic study.
Interplay between JA, SA and ABA signalling during basal and induced resistance against Pseudomonas syringae and Alternaria brassicicola
We have examined the role of the callose synthase PMR4 in basal resistance and β-aminobutyric acid-induced resistance (BABA-IR) of Arabidopsis thaliana against the hemi-biotrophic pathogen Pseudomonas syringae and the necrotrophic pathogen Alternaria brassicicola. Compared to wild-type plants, the pmr4-1 mutant displayed enhanced basal resistance against P. syringae, which correlated with constitutive expression of the PR-1 gene. Treating the pmr4-1 mutant with BABA boosted the already elevated levels of PR-1 gene expression, and further increased the level of resistance. Hence, BABA-IR against P. syringae does not require PMR4-derived callose. Conversely, pmr4-1 plants showed enhanced susceptibility to A. brassicicola, and failed to show BABA-IR. Wild-type plants showing BABA-IR against A. brassicicola produced increased levels of JA. The pmr4-1 mutant produced less JA upon A. brassicicola infection than the wild-type. Blocking SA accumulation in pmr4-1 restored basal resistance, but not BABA-IR against A. brassicicola. This suggests that the mutant's enhanced susceptibility to A. brassicicola is caused by SA-mediated suppression of JA, whereas the lack of BABA-IR is caused by its inability to produce callose. A. brassicicola infection suppressed ABA accumulation. Pre-treatment with BABA antagonized this ABA accumulation, and concurrently potentiated expression of the ABA-responsive ABI1 gene. Hence, BABA prevents pathogen-induced suppression of ABA accumulation, and sensitizes the tissue to ABA, causing augmented deposition of PMR4-derived callose.
β-Aminobutyric Acid-induced Resistance in Plants
The broad sprectrum protective effect of the non-protein amino acid β-aminobutyric acid (BABA) against numerous plant diseases has been well-documented in the literature. Here, we present an overview of BABA-induced protection in various pathosystems. Contriidictory reports concerning the mechanism of action underlying this type of protection incited us to take advantage of Arabidopsis/pathogen interactions as model systems to investigate the action of BABA at the genetic and molecular level. We present evidence that the protective effect of BABA is due to a potentiation of natural defense mechanisms against biotic and abiotic stresses. In order to dissect the pathways involved in potentiation by BABA describe the use of a mutational approach based on BABA-induced female sterility in Arabidopsis.