THE ARABIDOPSIS TT5 MUTANT ACCUMULATES NARINGENIN CHALCONE AND EXHIBITS ENHANCED RESISTANCE TO FUNGAL PATHOGENS WHEN GROWN UNDER LONG DAY CONDITIONS
Date
2021-10-04
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Journal ISSN
Volume Title
Publisher
ORCID
Type
Thesis
Degree Level
Doctoral
Abstract
Fungal diseases such as powdery mildew (Erysiphe cichoracearum) and anthracnose (Colletotrichum higginsianum) cause symptoms leading to death in many crop species. In order to stop the progression of diseases, plant species deploy several metabolites such as flavonoids. In this research, we used the model plant Arabidopsis thaliana to evaluate the effect of the Flavonoid Naringenin Chalcone (NC) against both pathogens. We discovered that when grown under long days, the tt5 mutant of Arabidopsis (which accumulates NC) exhibits reduced growth but enhanced resistance to the above pathogens. The TT5 gene encodes Chalcone Isomerase, a key enzyme in the flavonoid pathway which converts naringenin chalcone to naringenin. Observing the tt5 plant phenotype, we found that they exhibited increased cell death, callose deposition and reactive oxygen species (ROS) accumulation in leaves. They also constitutively expressed transcripts encoding the pathogenesis-related (PR) proteins: PR1 and PR5. To isolate the cause of these phenotypes, tt4 (Chalcone Synthase) and tt4/tt5 mutants were also examined. Neither exhibited pathogen resistance, cell death, callose deposition, ROS or PR expression phenotypes. When tt5 plants were grown under short days, they behave like wild type plants with respect to growth patterns, pathogen resistance, cell death, callose deposition, ROS accumulation, and PR expression. These responses correlate with the accumulation of naringenin chalcone, the compound expected to accumulate in tt5 plants. The same behavior was observed when tt5 plants were crossed with Salicylic acid (SA) insensitive mutants (sid2, nahG), except for tt5/sid2 that presented small traces of NC. Our results suggest a link between naringenin chalcone accumulation and SA signaling cascade during plant defense.
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Keywords
Flavonoids, Naringenin Chalcone, Plant defense, Fungal pathogens
Citation
Degree
Doctor of Philosophy (Ph.D.)
Department
Biology
Program
Biology