Tomato fruit wound inoculation by C. coccodes and ammonium treated

Experiment description: Colletotrichum coccodes secretes ammonium during germination and colonization of host tissue as a mechanism for dual activation of fungal pathogenicity factors and plant cell death via activation of host NADPH oxidase. Ammonium accumulation during colonization of tomato fruits by C. coccodes induced host nucleus integrity changes and program cell death (PCD). Transcriptome analysis at the leading edge of colonized tissue and ammonium treated tomato fruits revealed 82 and 237 common up-regulated and common down-regulated genes, respectively. The common-up-regulated genes showed over representation of pathogen related (PR) proteins, salicylic acid (SA) dependent and systemic acquired resistance (SAR) related genes and genes related to biotic stress. The down regulated genes showed over representation of Jasmonic acid (JA) dependent genes. Consistent with this observation the direct application of SA enhanced C. coccodes colonization, whereas the application of JA delayed colonization. Candidate genes were selected for QRT-PCR analysis of transcripts in normal and transgenic RBOH antisense plants and showed dependence on RBOH regulation. In all, the results suggest that ammonia accumulation during C. coccodes colonization activates SA and suppress JA pathways through activation of RBOH. The effects of ammonium on the expression of the selected up-and down regulated genes were examined in fruit of different maturation stages. Red, susceptible and green resistant, tomato fruit displayed similar behavior, suggesting that resistance of green fruits to C. coccodes colonization is not modulated by the JA and SA pathways but depends on other factors

Author: Robert Fluhr

Contact: Pierdomenico Perata (, Sant Anna School of Advanced Studies

External link: GEO