Flumorph Is a Novel Fungicide That Disrupts Microfilament Organization in Phytophthora melonis

Abstract

The mechanism of the effects of flumorph (a novel fungicide) was investigated by analyzing alterations of hyphal morphology, cell wall deposition patterns, F-actin organization, and other organelles in Phytophthora melonis. Calcofluor white staining suggested that flumorph did not inhibit the synthesis of cell wall materials, but disturbed the polar deposition of newly synthesized cell wall materials during cystospore germination and hyphal growth. After exposure to flumorph, zoospores were able to switch into cystospores accompanied with the formation of a cell wall, whereas cystospores failed to induce the isotropic-polar switch and did not produce germ tubes but continued the isotropic growth phase. In flumorph-treated hyphae, the most characteristic change was the development of periodic swelling ("beaded" morphology) and the disruption of tip growth. Newly synthesized cell wall materials were deposited uniformly throughout the diffuse expanded region of hyphae, in contrast to their normal polarized patterns of deposition. These alterations were the result of F-actin disruption, identified with the fluorescein isothiocynate (FITC)-phalloidin staining. The disruption of F-actin also was accompanied by disorganized organelles: each swelling of subapical hyphae was associated with a nucleus. Vesicles did not undergo polarized secretion to the apical hyphae, but diffused around nuclei for the subapical growth; thus, the cell wall was thickened with periodic expansion along the hyphae. Upon removing flumorph, normal tip growth and organized F-actin were observed again. These data, as well as data published earlier, suggest that flumorph may be involved in the impairment of cell polar growth through directly or indirectly disrupting the organization of F-actin. The primary site of action by flumorph in the disruption of the F-actin organization is under investigation.

Plant-Plant-Microbe Mechanisms Involved in Soil-Borne Disease Suppression on a Maize and Pepper Intercropping System

“…The inhibitory activity of root exudates and target compounds on colony growth of P. capsici was determined according to a previously published method [33] . Briefly, a fresh plug (5 mm in diameter) was taken from the growing edge of a carrot agar medium (CAM) (200 g boiled carrot and 15 g agar in a total volume of 1 liter of distilled water) culture and transferred onto CAM supplemented with root exudates (0, 0.06, 0.10, 0.5, 1.0, and 5.0 mg/mL) or target compound (MBOA, BZO, or MBZO) (0, 0.02, 0.1, 0.2, 0.6, and 1.0 mg/mL), respectively.…”

“…Colony growth was assessed by measuring the increase in colony diameter after incubation in darkness at 25°C for 4 days. The inhibition of root exudates or target compounds against colony growth was calculated [33] .…”

Mandipropamid targets the cellulose synthase‐like PiCesA3 to inhibit cell wall biosynthesis in the oomycete plant pathogen, Phytophthora infestans

“…, 2001, Reuveni, 2003), modifications in phospholipid biosynthesis (Griffiths et al. , 2003) or the disruption of F‐actin (Sheng Zhu et al. , 2007) as a primary mode of action.…”

“…Despite numerous attempts, the mode of action of CAAs has, until now, remained unknown. Several studies have described or suggested modifications of the cell wall structure (Cohen et al, 1995, Jende et al, 2001, Reuveni, 2003, modifications in phospholipid biosynthesis (Griffiths et al, 2003) or the disruption of F-actin (Sheng Zhu et al, 2007) as a primary mode of action.…”

A complex game of hide and seek: the search for new antifungals

“…More recently, Si and co-workers determined that flumorph is able to penetrate the cells and disrupt the organization of F-actin, which leads to alterations in cell-wall deposition. 46 …”