Aldaulactone – An Original Phytotoxic Secondary Metabolite Involved in the Aggressiveness of Alternaria dauci on Carrot

Frontiers in Plant Science

Romain Berruyer¹  Linda Voisine²  Latifa Hamama²  Mathilde Briard²  Mickaël Lecomte²  Pascal Poupard²  Séverine Gagné²  Julia Courtial²  Laurent Ogé²  Claire Yovanopoulos²  Yann Renaux²  Esteban Guichard²  Bruno Hamon²  Tristan Boureau³  Pascal Richomme⁴  Jean-Jacques Helesbeux⁴ 

[1] Département de Biologie, Faculté des Sciences, Université d’Angers, Angers, France;IRHS, INRA, AGROCAMPUS-Ouest, Université d’Angers, SFR 4207 QUASAV, Beaucouzé, France;PHENOTIC Platform, IRHS, INRA, AGROCAMPUS-Ouest, Université d’Angers, SFR 4207 QUASAV, Beaucouzé, France;Substances d’Origine Naturelle et Analogues Structuraux, SFR4207 QUASAV, UNIV Angers, Université Bretagne Loire, Beaucouzé, France;

关键词: Alternaria leaf blight;    aggressiveness;    fungal pathogenicity;    in vitro culture;    phytotoxin;    quantitative disease resistance;   

DOI  :  10.3389/fpls.2018.00502

来源: DOAJ

【 摘 要 】

Qualitative plant resistance mechanisms and pathogen virulence have been extensively studied since the formulation of the gene-for-gene hypothesis. The mechanisms involved in the quantitative traits of aggressiveness and plant partial resistance are less well-known. Nevertheless, they are prevalent in most plant-necrotrophic pathogen interactions, including the Daucus carota–Alternaria dauci interaction. Phytotoxic metabolite production by the pathogen plays a key role in aggressiveness in these interactions. The aim of the present study was to explore the link between A. dauci aggressiveness and toxin production. We challenged carrot embryogenic cell cultures from a susceptible genotype (H1) and two partially resistant genotypes (I2 and K3) with exudates from A. dauci strains with various aggressiveness levels. Interestingly, A. dauci-resistant carrot genotypes were only affected by exudates from the most aggressive strain in our study (ITA002). Our results highlight a positive link between A. dauci aggressiveness and the fungal exudate cell toxicity. We hypothesize that the fungal exudate toxicity was linked with the amount of toxic compounds produced by the fungus. Interestingly, organic exudate production by the fungus was correlated with aggressiveness. Hence, we further analyzed the fungal organic extract using HPLC, and correlations between the observed peak intensities and fungal aggressiveness were measured. One observed peak was closely correlated with fungal aggressiveness. We succeeded in purifying this peak and NMR analysis revealed that the purified compound was a novel 10-membered benzenediol lactone, a polyketid that we named ‘aldaulactone’. We used a new automated image analysis method and found that aldaulactone was toxic to in vitro cultured plant cells at those concentrations. The effects of both aldaulactone and fungal organic extracts were weaker on I2-resistant carrot cells compared to H1 carrot cells. Taken together, our results suggest that: (i) aldaulactone is a new phytotoxin, (ii) there is a relationship between the amount of aldaulactone produced and fungal aggressiveness, and (iii) carrot resistance to A. dauci involves mechanisms of resistance to aldaulactone.

【 授权许可】

Unknown