Abstract Detail


Salley, Maggie [1], Ferraro, Anna [1], McCormick, Bailey [1], Wommacck, Andrew [2], Hughes, Nicole Michelle [3].

Characterizing plant biochemical responses to pathogenic stress: a spotlight on red leaf spots.

Red leaf spots commonly accompany pathogen infection in plants. Yet, the function of red anthocyanins pigments in infected tissues is unknown. We characterized biochemical responses of two plant species, red-tip photinia (Photinia glabra) and Indian hawthorn (Rhaphiolepis indica), to infection by the pathogenic fungus, Entomosporium mespili. We used analytical HPLC and LC-MS to identify and quantify anthocyanins and photopigments in red leaves or tissues (including red expanding leaves, red senescing leaves, and red spots) and green tissues (green areas around red spots, fully-expanded green leaves) of the same plants. Maximum quantum yield efficiency of PSII (Fv/Fm) and xanthophyll cycle pigment ratios was measured as a proxy for sustained high-light stress. DPPH radical scavenging assay assessed low molecular weight activity (LMWA) in red spots versus surrounding green tissues. The major anthocyanins in red tissues of both species were cyanidin-3-O-galactoside and cyanidin-3-O-arabinoside. Red tissues of photinia also contained small amounts of three additional cyanidin mono-glycosides (cyanidin-3-O-glucoside and two unidentified cyanidin-O-pentosides); red spots lacked cyanidin-3-O-arabinoside. All red tissues had significantly lower chlorophyll and Fv/Fm than green tissues, suggesting increased vulnerability to photo-oxidative stress. Photoprotective carotenoids did not differ between red and green tissues, likely due to small sample size. Antioxidant activity was 1.5-3.4x higher in red spots versus surrounding green tissues; follow up assays with purified anthocyanins suggested anthocyanins were responsible for ca. 1/3 antioxidant activity in red spots. From these results, we predict the function of anthocyanins in red spots is similar to anthocyanins in young and senescing leaves, and this function likely includes photoprotection (i.e. light attenuation and antioxidant defense). We are currently investigating a possible anti-microbial function as well.

1 - High Point University, 1 N University Pkwy, High Point, NC, 27268-0002, USA
2 - High Point University, Department of Chemistry, 1 N University Pkwy, High Point, NC, 27268-0002, USA
3 - High Point University, Department of Biology, 1 N University Pkwy, Wanek Natural Science 311, High Point, NC, 27268, United States


Presentation Type: Poster
Number: PPM003
Abstract ID:863
Candidate for Awards:Phytochemical Best Poster Award

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