P-691 - Observations in cercosporin sequestration and hyphal morphology in high- and low-toxin producing Cercospora cf. flagellaris isolates

Monday, August 4, 2025

4:30 PM - 5:15 PM HST

Location: Exhibit Hall 3

Presenting author(s)

BC

Beatriz M. Carvalho

Postdoctoral Researcher
Department of Plant Pathology & Crop Physiology, Louisiana State University
Baton Rouge, LA, USA

Author(s)

MC

Maria Izabel Costa de Novaes

LSU
Baton Rouge, Louisiana, United States
PD

Pedro Henrique Dias dos Santos

Postdoctoral Researcher
Department of Plant Pathology & Crop Physiology, Louisiana State University
Baton Rouge, Louisiana, United States
VD

Vinson P. Doyle

Associate Professor
Department of Plant Pathology & Crop Physiology, Louisiana State University, Baton Rouge, LA 70803
Baton Rouge, Louisiana, United States
ST

Sara Thomas-Sharma

Assistant Professor
Department of Plant Pathology & Crop Physiology, Louisiana State University
Baton Rouge, Louisiana, United States

Abstract Text: Cercosporin, a light-activated perylenequinone toxin, is a key virulence factor for Cercospora spp. causing Cercospora leaf blight on soybean. Cercosporin generates reactive oxygen species that damage host tissue but does not harm the producer. Self-resistance to cercosporin is known to involve maintenance of the toxin in a reduced state within the cytoplasm. Yet another mechanism of self-resistance was observed in a high-cercosporin producing C. cf. flagellaris isolate, where active cercosporin was sequestered in lipid droplets of thin hyphae. In contrast, a low-cercosporin isolate produced only thick hyphae and no cercosporin. Here, we used optical and confocal microscopy to study three C. cf. flagellaris isolates classified as high (0.040–0.045 mM) or low (0.025–0.029 mM) cercosporin producers. After 24 h on PDA, active and reduced cercosporin was detected only in isolate 6020MRL (high), however all isolates formed thin hyphae. By 48 and 72 h, only isolate DMCC1741 (low) did not produce any form of cercosporin. By 72 h, active cercosporin was present in five isolates, thin hyphae ( < 5 µm) were not exclusive to high producers, and their frequency did not correlate with cercosporin levels. These results suggest that hyphal morphology and cercosporin production differed considerably between isolates categorized as low-/high- cercosporin producers. Experiments are underway to study toxin sequestration, hyphal morphology, and cercosporin production of other Cercospora spp. and on different media to determine the generalizability of these observations.